Detection and Radiological Imaging of SLN 6

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In many tumor diseases, locoregional recurrence after operation is a serious problem, and is always a shock to patients and doctors alike.

The problem of locoregional recurrences is also especially important when the patients are treated by breast-conserving surgery, because locoregional recurrences occur even in approximately 10% of cases where primaries are small (pT 1a±1c) and homogeneous radiation therapy has been delivered to the remaining breast. When all operable breast cancers are considered together, the locoregional recurrence rate increases to ranges of upto 35%

(Rauschecker et al. 2001).

New approaches with the aim of improving or solving this problem are therefore a high priority.

In this context, improvements are necessary to make it possible to attain R0 resection (controlled by surgeons in consultation with the acting pathologists) by intraoperative histopathological examination of the margins of the lumpectomy or wide excision specimens and of the margins of any further marginal excisions around the primary ex- cisate, e.g., in cases with an extensive intraductal component (EIC) or direct cancer infiltration reaching parts of the margins of the primary exci- sate.

In addition, continuous excision of the blue dye- and ^99mTc-marked or -labeled strand(s) con- taining the draining lymphatics seems to be important for the attainment of maximum locoregional cancer clearance.

Such new approaches in tumor treatment are often published on the Internet and also discussed on television, where new guidelines can be re- ceived by doctors and patients simultaneously. This leads to frequent questioning of doctors about the quality of such new diagnostic and treatment protocols and the success achieved with them. There- fore, it is now more important than ever before for all medical specialists involved in patients' cancer treatment to keepfully informed and upto date with new ideas and techniques. The new sentinel

node approach is one such theme, challenging medical doctors working in a broad field of cancer diagnosis and treatment; its application is cur- rently in the course of being extended from melanoma and breast cancer to head and neck cancers, gastrointestinal cancers, and both male and female urogenital cancers and now involves nearly all surgical disciplines.

When in breast-conserving therapy protocols axillary revision with postoperative complications (bleeding infections, seroma formation, lymphede- ma etc.) can be largely avoided and atypically located sentinel nodes and/or sentinel nodes in different basins can be detected, these facts indicate that breast cancer treatment has been highly bene- ficial. Apart from this, in the case of a false-negative diagnosis, e.g. on the grounds of examination of the axillary lymph nodes, it is well known that the development of local and regional recurrence makes both doctors and patients afraid that the primary tumor is progressing and the prognosis is therefore poorer.

Initially there was a great deal of enthusiasm for the sentinel node concept, but doctors soon had to realize that good practice is not simple and that there are many aspects needing consideration, while good interdisciplinary cooperation and improvements are necessary before these methods, some of which are quite new, can be successful in all hospitals in which tumor treatment is carried out and which claim to provide optimal quality care (centers of excellence). The objective that the development of a simple, minimally invasive, technique for determining whether regional node metastasis has occurred, was clearly formulated by Krag et al. (1995) early in the emergence of the sentinel node concept and its application in patients with melanoma. This formula also fits in with most other cancer entities and in many clinics is already optimized by support from exist- ing well-defined guidelines (Krag et al. 1995; Al- bertini et al. 1996; Veronesi et al. 1997; Borgstein Chapter 6

Detection and Radiological Imaging of SLN 6

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et al. 1998; Cascinelli et al. 1998; Cox et al. 1998;

Leong et al. 1998; Paganelli et al. 1998).

It is still too early to intensify the spread of these new interdisciplinary approaches, including all techniques for blanket coverage, because in most countries processes for technical updating and development of local and multicenter studies are still only just being devised and set up, and experiences of at least some of the approaches are no more than preliminary.

Furthermore, there are some important points that need further clarification.

One of these is tumor cell clearance in continuity between the primary cancer and the sentinel node(s); another is, for instance, good practice in the investigation of sentinel node(s) in breast cancers with parasternal node(s) located along the mammaria interna blood vessel strands.

Nonetheless, it seems clear that the most important preconditions for good end-results are high- precision work and close cooperation among specialists in nuclear medicine, surgeons, and pathologists. On this very point, Glass (2001) has recently stated very clearly that lymphoscintigraphy and radioguided surgery are now also valuable tools that can be used in contemporary surgical staging of malignancies, continuing with the warning that these techniques require attention to detail and a moderate level of experience for optimal clinical use. Glass encourages cooperation of teams. He emphasizes that the wide use of these procedures has demonstrated that the methodolo- gy can be learned with guidance from a few dozen cases. Accuracy in use significantly enhances the sentinel node technique.

Discussion continues about the question of whether the sentinel node alone should be histo- pathologically evaluated and what distinguishes the cases in which it is necessary to investigate all nodes in the basin concerned.

At first view this does not seem to be a difficult question, as the current literature demonstrates.

However, in some specific regions, such as the axilla and the pelvis, the nodes are so closely packed together that at level I of the axilla, for instance, 3±5 nodes can all be sentinels and these nodes cannot be clearly separated by the gamma camera.

In contrast, with the blue dye method it is easier to separate the nodes (Fig. 1a).

When radiolabeling methods alone are used (Fig. 1 b), however, and on the grounds of these we would accept basin clearance by extirpation of

the nodes at level I ± thinking that the sentinel node(s) are included in this group± we incline to the opinion propagated years ago by the Rotter- dam-Breast Cancer Research Groupthat only the level I lymph node group should be removed.

Most research groups have not found only one sentinel node in the axillary basin: on average just under or over two nodes have been found.

Because the use of different labeling solutions results in different speeds of passage through level I lymph nodes to nodes of level II, it is not clear to what extent published results are comparable.

Furthermore, detection of multiple sentinel nodes in different levels of the same basin is critical with regard to strategies on further removal (Fig. 1c).

From these discussions it follows that the work carried out with reference to the sentinel node concept must be done very precisely.

The ªcontinuityº between the primary and the sentinel node(s) is a serious problem in cases with malignant melanomas of the foot and lower leg draining to the inguinal nodes. Such long pathways of the lymphatics not uncommonly lead to a predisposition to the development of so-called transit metastasis with no possibility of precalcu- lating the likelihood. There are a great many other incalculable problem areas in addition to this one.

In particular, the drainage pathways of cancers localized in the upper respiratory tract or within the oral cavity are not always calculable, which means the draining lymph nodes and the lymphatics to them cannot be easily reached by a surgical approach. The same is true for cancers of the gastrointestinal tract and the pelvic region.

Methodical Work-up and Improvements

The range of stains and radioactive substances that can be used for labeling is well developed, but there is still room for improvement. It is also not clear how probe and tracer techniques can be combined.

One novel procedure in this connection is the radiological investigation of lymph nodes with iron oxide used for labeling of the sinus histiocytes to find defective areas of nodes with tumor infiltration (point 1 in Table 1).

In addition, the problem of the injection route has not been entirely solved. It seems important that most hospitals have not accepted intratumoral

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Methodical Work-up and Improvements 41

Fig. 1a±c.Visualization of lymphatics and the sentinel node(s) using blue stain (patent blue) and exact localization by the use of^99mTc-nanocolloid.

aWith free sight of the blue-stained lymphatics and blue-stained sentinel lymph nodes (SLN) the path of locoregional spread can be defined precisely.

bImaging and labeling (lymphoscintigraphy) allow precise localization of the SLN. Total excision can be controlled by use of a gamma probe. Note that in cases with centrally located primaries the singular SLN can be located in the axillary basin. [Figure kindly made available by Professor Paganelli, Milan, Italy: Detection of a solitary SLN in the axilla (^99mTc-nanocolloid).]

cIn this case too-small colloid particles were used; the radiolabeled particles passed through the SLN too quickly and accumulated in subsequent nodes (high ªspilloverº)

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injection of labeling substances and/or solutions.

This can be fully understood on two grounds:

1. An acute increase in hydrostatic pressure can open small veins, pressing tumor cells into the vascular lumina with a consequent increase of metastatic potential.

2. The lymph vessels are much more highly developed in the tumor periphery than in its central parts (point 2, of Table 1).

For visualization of the connection of primaries with their sentinel nodes the best method is the use of blue stains; but detection of the sentinels is increased by labeling with ^99mTc used as a tracer;

therefore, a combination of both methods is preferred by many working-groups who are interested in sentinel node detection and investigation.

A further point is improvement of the detection systems (point 3, Table 1) and kinds of imaging.

In addition, there are new approaches that pathologists can apply.

· For confirmation of the diagnosis of the primary made with the aspiration biopsy or punch biopsy techniques.

· For evaluation of the sentinel nodes.

± Exact statistically significant evaluation procedures are needed for SLNs. This demand implicates the key question of how many sections are needed and how far apart they must be to increase reliability in exclusion or confirmation of metastatic involvement.

± Evaluation of combined H&E staining and immunohistochemical reactions.

± Evaluation of RT-PCR techniques for cancer cell detection in sentinel nodes (see point 4d, Table 1).

Table 1.Favorite pharmaceuticals for routine use as tracers for sentinel node detection 1) Pharmaceuticals and tracers used for sentinel node detection

a) Blue dyes and others Patent blue

Indigo carmine blue dye (see Kim et al. 2001) Isosulfan blue dyes

(Lymphazurin ± specifically used for colored N-staging) see Waters et al. 2000 Wiese et al. 2000 Paramo et al. 2001 Saha et al. 2001 b)^99mTc-labeled compounds:

99mTc-nanocolloid

99mTc-human serum albumin

99mTc-tin colloids see Kim et al. 2001

c) Iodine-125 for staging of differentiated thyroid cancer (see also Chapter 22)

d) Systemically administered compounds:

Ultra small particles of iron oxide (USPIO) (see also Chapter 19) 2) Modalities of injection

a) Intradermal (breast cancer, malignant melanoma) injection is preferred in the majority of breast cancers because also from deeper areas of the parenchyma the lymphatics drain first to superficial regions and then to the sentinel nodes

b) Peritumoral injection is compatible with deeply located primaries which can drain to interpectoral nodes c) Intratumoral injection has been practiced in the very early stages of the sentinel node concept developed, but hen

widely left because of warning signals that the tumor spread can be propagated by this application modality But now, in cases with non palpable breast cancers and diffuse cancer growth, showing very limited extension injection of a small portion of the labeling solution into the cancer area is carried out by some groups, in order to recover the lesion intraoperatively more precisely. This strategy has been called radioguided occult lesion localization (ROLL)

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The ambitious new approaches to more intensive investigation of the SLN(s) than of the excised lymph node groups when lymph node staging is practiced indicate positive developments in lymph node staging.

Nonetheless, when this procedure is practiced with the object of a high degree of safety in detection at least of small tumor cell areas (clusters), a large number of sections of the sentinel node must also be stained immunohistochemically with antibodies (e.g. against cytokeratins, or S-100 protein and other markers). As long as such investigations are covered by clinical research programs the results will be optimal, because these investigations are important factors in scientific success. How- ever, when such investigations are introduced into clinical routine programs and there are no rules for adequate payment (payment for primary or secondary antibodies, technicians, etc.), these extremely sophisticated and intensive investigations cannot be performed, or if they are, because no adequate payment is made for them, we have to fear that they are not correctly done.

Harmonization in the usage of tracer substances is a difficult problem both technically and also le- gally, in view of the differing laws among the na- tions throughout the world.

Because the background preconditions are so inhomogeneous, international and comparative studies are difficult to perform.

It seems that in the United States and also in some European countries the diversification of tracer development is much more advanced than in Germany. However, it seems that as the Europe- an integration progresses, some of the problems will be solved. Besides the radiolabeled tracers, the development of colloid particle production and re-

search on adaptation to clinical performances seem to be in progress.

Techniques in Sentinel Node Detection Tracers and Application Modality

A large number of tracers and carrier solutions have been used in experimental and routine studies, but few of the pharmaceuticals have proved suitable for development for standard use. Their limited suitability depended mostly on their quality and was based at least partly on the requirements that they

· Involve no toxicity or genetic injury to the patient and extremely low antigenicity, in order to avoid allergic or anaphylactic reactions as far as possible

· Be largely innocuous in terms of radioactive injury to medical and nursing staff as well as patients

With due consideration for all this, the following compounds can be seen as the favorites for routine usage (Table 1).

Intraoperative Sentinel Node Detection by Use of the Gamma Probe

Figure 2 demonstrates roughly the different components of a gamma probe unit. The collimator takes upthe signals coming from the labeled SLN.

The signals are then sent to the scintillation crystal Intraoperative Sentinel Node Detection by Use of the Gamma Probe 43

Fig. 2a,b.Collimator, with the honey- comb structure of its face(a)and per- pendicular side view(b)is shown. The gamma rays pass through the collimator and are detected within the scintillation crystal photo-multiplier assem- bly

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and led through the photomultiplier tubes to the measuring instruments.

Dedicated processing components determine the gamma ray energy and its location.

The kind of imaging influences the diagnostic result. It can be dynamic, early, or early and late.

Efforts at Optimization in^99mNanocolloid- Mediated Sentinel Node Localization

Van Dongen's group(Gommans et al. 2001) tried to optimize^99mTc-nanocolloid sentinel node detection in breast cancer cases by improving the count rate by use of higher specific concentrations of ^99mTc- colloidal albumin, with increased radiochemical labeling efficiency and stability. The particle size of colloidal albumin was tested by dynamic light scat- tering at angles of 30.28, 62.68, and 908. For labeling under nitrogen a maximum acceptable concentra- tion of 10 MBq/lg was found, which complies with the specifications of the manufacturer, when the labeling was carried out in vacuum vials; 2.5-fold radiochemical labeling efficiency over the entire period was achieved, and a significant improvement (P<0.002) was found in vivo.

The investigators concluded that, although the rate of successful visualization of the SLN was high, the count rate achieved with the highest con- centration of ^99mTc-colloidal albumin was 9 times as high. This facilitated SLN detection by the gamma probe during surgery.

Histo- and Cytopathological Diagnosis

It is beyond doubt that the sentinel node approach sometimes restricts the conventional histopathological diagnosis, which has to be made on the basis of primary tumors.

The highest degree of limitation exists in the diagnosis of malignant melanomas. As a rule, in practice this tumor is often removed in toto with an adequate safety margin before the sentinel node search is started (see also Chapter 25).

In breast cancer the diagnostic results obtained by radiodiagnosis (mammography, MRI) can be supplemented or complemented by the use of fine- needle aspiration cytology (FNAC) before SLN labeling takes place.

We cannot recommend a routine strategy in which lumpectomy/wide excision is first performed for removal of the primary and the sentinel nodes are then labeled by the blue dye method and/or

99mTc-nanocolloid labeling, because by then the drainage ways may have changed as a result of operation-related local injuries. Such strategies would have been limited to subdermal injection topogra- phically corresponding to the location of the primary.

In surface cancers of the epidermis and mucosa (mostly squamous cell cancers) in the head and neck regions and oropharynx or vulva, the use of exfoliative cytology or minibiopsies can help to confirm the cancer diagnosis before the sentinel node biopsy procedure is started.

In the diagnosis of lung cancer, verification of non-small-cell type (nSCLC) and exclusion of small-cell type (SCLC) is possible preoperatively in more than 90% of cases, when endoscopic biopsies and/or cytology methods are applied before N-staging followed by sentinel node search procedures, which can be further extended by intraoperative N-staging before lobectomy or pneumectomy.

In the case of gastrointestinal cancers or neuroendocrine cancers, the diagnosis is most frequently confirmed by investigation of endoscopi- cally taken biopsy specimens.

In prostate cancer treatment sentinel node labeling with ^99mTc-colloids is not limited by needle biopsies taken before N-staging is carried out.

The histopathological and both cytopathological and immunohistochemical spectra for confirmation of cancer and biological analyses ± critically evaluated in chapter 30 is summarized in Table 2.

Table 2 gives an overview of the spectrum of histo- and cytopathological possibilities for confirmation and subtyping of cancer and the evaluation of prognostic factors

Sun et al. (2001) compared the efficiency of

99mTc MIBI single photon emission computed tomography (SPECT) and computed tomography in head and neck cancer patients in whom involvement of cervical lymph nodes was suspected. In 40 of 50 patients with nasopharyngeal cancers (NPC) cervical lymph node involvement was detected. For 22 lymph node lesions there were discrepancies in the results between ^99mTc MIBI-SPECT and CT

99mTc, and in these MIBI SPECT correctly detected 5 metastatic and 7 benign lymph node lesions.

99mTc MIBI SPECT and CT correctly detected all of the 18 metastatic lymph node lesions. In total,

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Histo- and Cytopathological Diagnosis 45

Table2.Importantprognosticfactorsandlabelingproceduresforsentinellymphnodes(SLN) Cancertype(s) Verification subt

ypingDifferentiation products/gradingProliferationactivity S-phaseImprint+FNACProceduresusedfor cancercelldetect. inSLN

Labelingprocedures BreastcancerHandE-stainingCK 8,18. /.CD68allow discriminationof cancercellsfrom histiocytes.Actin labelsmyoepithelial cells

Estrogenandpro- gesteronereceptor (stainingintensity; %ofpositivecells c-erbB2(p185) cathepsinD(bioch.) MIBI(Ki67)after microwaveprepara- tionKiS1lowprolif- erationmedium, highproliferation photometricS-phase FNACpossible smearfrom mammillaesecretion possible Serialsectionsof thewholeSLN(s) HE,CK8,18,RT, PCRpossible

Bluedye(patent blue)and/or 99m Tc-nanocolloid Malignant melanomaHE,vimentin, HMB45,S100 protein. MelanA/Mart-1

Lowrateofc-erb B2-positivecasesMIBI,KiSI,S-phase, ploidynopuncture(con- traindicatedbecause ofposs.spread)

HE,HMB45,tyrosinase-RT-PCRbluedyeand/or 99mTc-nanocolloid Head,neckand oropharyngeal cancers

HE,CK,5,6for squamouscell cancers CK8,18foradeno- carcinomas Degreeofmalig- nancy(G1±G3)MIBI,KiSI,S-phase, ploidyExfoliativeand FNACcytologySerialsectionsCK5, 6forsquamouscell cancers;CK8,18for adenocarcinomas

Bluedyeand/or 99mTc-nanocolloid alternatively: 99mTC-methoxy- isobutylisonitrile (99m Tc-MIBI) Genitalcancers Female:vulva,cervix Male:penilecancer

HE,CK5,6for squamouscell cancers Degreeofmalig- nancyc-erbB2in cervicalcancers MIBI,KiSI,S-phase, ploidyExfoliative,cytologySerialsectionsCK5, 6forsquamouscell cancers CK8,18forendo- cervicalcancers

Bluedyeand/or 99mTc-nanocolloid Non-small-celllung cancer(nSCLC)HE,CK5,6for squamouscell cancers CK8,18,19for adenocarcinomas

Degreeofmalig- nancyc-erbB2MIBI,KiSI,S-Phase, PloidyExfoliativecytology andFNACbesides biopsyuseful Serialsectionscyto- keratin±staining (CK5,6forsqua- mouscellcancer CK8,18,19forade- nocarcinoma

Viamediastinos- copyorendoscopic orsystemic (Sinerem),alsoby useofFDGPET Gastrointestinal cancersHE,CK8,18Degreeofmalig- nancyadenocar- cinomavsdiffuse typec-erbB2

MIBI,KiSI,S-Phase, PloidyExfoliativecytology possibleSerialsectionsCK8, 18

99m Tc-nanocolloid Neuroendocrine cancersHE,cytokeratin (pan),neuromarkersDegreeofmalig- nancyS100-protein chromograninA synaptophysin

MIBI,KiSI,S-phase, ploidyExfoliativecytology possibleSerialsectionsS100, chromograninAHardlyanyexperi- enceavailable ProstatecancerHE,capsular infiltrationor perforation

Gleasongradeacid prostatephosphatase, prostate-specific antigeninthecase ofmarkerlossalso CK(pan),P504S MIBI,KiSI,S-phase, ploidySixsitepuncture (biopsies),checkat onceinbiopsycylin- derswhethercapsule tissueisinvadedby cancer SerialsectionsHE andpan-cytokeratin

99m Tc-nanocolloid

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99m Tc MIBI SPECT showed better specificity but lower sensitivity than CT in detecting cervical lymph node metastases in NPC.

MAGE-A3 Marker Function in Breast Cancer Patients Sentinel Node Evaluation

There have been attempts to detect occult cancer cells by RT-PCR, with tyrosinase in malignant melanoma cases and with MAGE-A3 in breast cancer cases.

Whereas many approaches to RT-PCR detection are limited by poor specificity, MAGE-A3 seems to be a highly specific tumor mRNA-marker, which is not expressed in noncancer cells.

In recent investigations by Wascher et al.

(2001), 77 AJCC stage I±IIIa breast cancer cases were analyzed. The results of this study are summarized in Table 3.

MAGE-A3 mRNA expression in the SLN occurred more frequently with infiltrating lobular carcinomas than with infiltrating ductal carcinomas (P<0.001). Use of MAGE-A3 mRNA in the development of antigen-specific targeted immu- notherapy has been planned. Basically, it is beset by the same difficulties as tyrosinase RT-PCR eva- luations in SLN material from patients with malignant melanomas.

It is possible that the tumor marker MAGE-A4 is not derived exclusively from vital melanoma cells, but can also be present in apoptotic or ne- crotic melanoma cells.

Retrospective Evaluation of the Significance of SLN Located Mediastinally or Along the Mammaria Interna by Radioimaging

Eubank et al. (2001) conducted a retrospective investigation into the question of mediastinal or internal mammary metastases in breast cancer patients, using FDG-PET and CT in 73 consecutive patients with recurrent or metastatic breast cancer.

Both CT and FDG-PET were carried out within 30 days of each other.

Overall, 40% of the patients had abnormal mediastinal or internal mammary (IM) FDG-uptake consistent with metastases, compared with 23% of patients in whom enlarged mediastinal or internal mammary (IM) nodes giving rise to suspicion were disclosed by CT. Both FDG-PET and CT were positive in 22% of these patients.

In the subset of 33 patients with assessable follow- up by CTor biopsy, the sensitivity, specificity and accuracy for nodal disease were 85%, 90%, and 88%, respectively, according to FDG-PET; 54%, 85% and 73%, respectively, according to prospective interpretation of CT; and 50%, 83% and 70%, respectively, by blinded observer interpretation of CT.

Among the 33 patients in whom locoregional disease recurrence only was suspected also had un- suspected mediastinal or IM disease according to FDG-PET. The inescapable conclusion to be drawn from this well-documented series is that FDG-PET can uncover nodal involvement in these nodal regions that has not been recognized by conventional staging methods.

These preliminary results should be further val- idated by prospective histo- and cytopathological studies in the future.

Suspicion of IM node involvement by locoregional cancer spread seems to be an important point in implication of this node group in the radiotherapy field of treatment and/or adjuvant chemotherapy treatment protocols.

Table 3.Analysis of breast cancer cases classified as stages I±IIIa (AJCC system; Wascher et al. 2001) Number of

cases investi- gated

Marker No. of positive nodes, HE and/or IHC

No. of nodes in analyzed series

Histologically negative SLN but positive for MAGE-A3

Overall positive cases for MAGE-A3

SLN positive cases for MAGE-A3

77 MAGE-A3 48/121

40% 35/77

45% 28/73

38% 41/77

53% 50/121

41%

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Siddon et al. (1982) underscored the utilization of parasternal lymphoscintigraphy in radiation therapy of breast carcinoma.

The decision to pursue the internal mammary nodes (IMN) has long been a source of contro- versy. Dupont et al. (2001) mapped 1,470 cases to correct the N-staging and determine the therapeu- tic consequences the mistaken staging had had for therapy.

It is important to recall that mapping to the IMN basins with a finding of metastasis means stage N3-disease according to the current staging system.

In Dupont's series 5 (14%) of 36 cases with sentinel nodes in the IMN basin had to be upstaged and more frequently had multiple positive IMNs.

These patients then had additional radiation therapy.

Inclusion and Exclusion Criteria for Sentinel Node Investigation

These criteria are very important: they have been intensively evaluated for breast cancer and also for malignant melanoma, but for many other cancers only rare certified results are available.

In breast cancer cases, as a rule it makes sense to look for the SLN only when the diagnosis of the primary is secure according to mammography and/or MRI or has been confirmed at least cyto- logically. This can be achieved by punch or aspiration biopsy, perhaps including evaluation of so- called prognostic factors such as ER and PR status, c-erbB2 overexpression, mutated p53 expression or vimentin expression (Domagala et al. 1990). In

breast cancer series with vimentin coexpression, Domogala et al. found an association with low or missing estrogen and/or progesterone receptor expression and high proliferative activity measured with the antibody Ki-67 (1990 a), a worse prognosis even in node-negative cases (1990 b) and an association with a high degree of malignancy (1990 c).

Cases with local multifocality can be included in the sentinel node detection regimen, because these foci are by definition located close together and therefore drain into the same basin in most cases, in addition to which multifocality is often found by MRI or intraoperatively when the primary is excised. However, as MRI investigation techniques become more advanced it is becoming more and more possible also to find small tumor foci around the primary and with this a higher rate of the ªstate of multifocalityº even before surgery. This is an important point and should be taken upwhen radiological diagnosis (MRI) has already raised the suspicion of multifocality.

In cases with multicentricity involving the development of tumor nodes in different quadrants, sentinel node examination is generally pointless, because in most cases mastectomy is the method of choice and multicentric intradermal and/or peritumoral injections of ^99mTc would need too high a total dosage. Only when parasternal nodes must be suspected as target nodes more often but not exclusively in medially or centrally localized primaries can labeling of these foci by peritumoral injection and looking for parasternal SLN (along the IM) be of value with respect to postoperative radiation and/or chemotherapy. The exclusion criteria for SLN investigation are summarized in Ta- ble 4. In position I the assessment criteria (triple Inclusion and Exclusion Criteria for Sentinel Node Investigation 47

Table 4.Specific tumor types and axillary conditions in which looking for sentinel nodes is unreasonable and in which it should be carried out

a) Multicentric cancers in different quadrants As a rule should be excluded with regard to resection.^a The safest strategy is still mastectomy and axillary revision at levels I and II

b) Clinically positive axillary nodes Enlarged, indurated and immobilized nodes. Confirmation by aspiration or punch biopsy in questionable cases c) Clinically visible lymphangiosis carcinomatosa Confirmed by biopsy

d) Inflammatory breast cancer

Previous breast surgery with extensive scar formation Confirmed by biopsy

Accumulation of fluid in scar formations can lead to wrong or false results

aFor exceptions see Chapter 21

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diagnosis) are summarized as preconditions for sentinel node labeling with blue dye and/or ^99mTc- nanocolloid.

In position II the requirements for labeling mul- tifocal cancers are summarized. In cases with multicentric cancers peritumoral labeling can only be useful for adjuvant radio- and/or chemotherapy (III) (Fig. 3).

Criteria for Clinical and Histopathological Sentinel Node Evaluation (Breast Cancer)

In contrast to the clearly defined conditions in which sentinel node search and detection are helpful to avoid axillary revision in levels I and II and exceptions in which parasternal location of the sentinel node(s), for instance in cases with multicentric, partly centromedially localized cancers is helpful with regard to far-reaching decision making, there are clearly defined entities in which the search for sentinel nodes is contraindicated.

These constellations are summarized in Table 4, which also gives an overview of specific tumor subtypes and axillary conditions in which sentinel node search is unreasonable or not indicated or should not be carried out.

Recurrence rates in cases with breast cancers in central or retroareolar locations and treated by mastectomy or lumpectomy are still under discussion.

In their follow-upstudies (99 patients) Simmons et al. (2001) found a 4.8% (2 of 42 patients) local recurrence rate 3 years after mastectomy and a 4.8% recurrence rate (1 of 21) 5 years after lumpectomy.

In cases with subareolar cancers the local recurrence was 1 of 25 (4%) for patients undergoing mastectomy and 1 of 11 (9.1%) for patients undergoing lumpectomy (P>0.99).

The authors concluded that lumpectomy is a rea- sonable treatment option for selected patients with central or retroareolar breast cancers. On the basis of these still preliminary results ± which are based on a relatively small number of cases ± it can be concluded that in selected cases with subareolar cancers regardless of the surgical option (mastectomy or lumpectomy) sentinel node labeling is a helpful strategy for further decision making.

Recently, Macmillan et al. (2001) tried to test the relative benefits of the sentinel node concept and of the four node axillary sampling technique already tested 10 years ago by the Rotterdam groupand now called 4 NAS, in breast cancer.

This approach has already been abandoned throughout the world in view of the possibility of skipmetastases or metastases bypassing these nodes. Macmillan's groupinvestigated 200 breast cancer cases. A sentinel node (SN) was found in 96%. The SN was contained in the 4NAS in 153 cases (80%) and identified separately in 38 cases (20%).

That means that 20% of the SNs are not included in the 4NAS biopsy material. Finally, 49 of

Fig. 3.Criteria for clinical and histopathological sentinel node evaluation (breast cancer)

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the 60 node-positive patients were positive according to 4NAS and SN biopsy. The SN was not identified in 2, and in 8 the SN was falsely negative compared with 4NAS. For 1 patient the SN was positive and the 4NAS were negative.

The authors conclude from these results that SNB has no advantage when nodes are assessed by standard histological investigation, but the results of Macmillan's groupalso demonstrate clearly that the SLN concept is really superior to 4NAS procedure.

Furthermore, these results indicate that the SN concept cannot be practiced using simple routine techniques, but needs serial sectioning of the SN(s) and usage of immunohistochemistry for single cancer cell detection in the SLN.

Comparative Experimental Tracer Studies

99mTc is now the most used tracer and was introduced many years ago for SLN detection.

But is it really the best?

For further elucidation comparative animal-related studies were started (Edina et al. 2001). The investigators compared the uptake of^99mTc-labeled human serum albumin colloid (^99mTc HSAC),

99mTc-labeled antimony sulphur colloid (^99mTc-SC), and a ^99mTc-labeled dextran 70 solution (^99mTc- DX) and their selectivity in identification of the sentinel node(s) of normal mice and tumor-bearing mice.

After injection into the footpad, the radiopharmaceutical uptake in the SLN (popliteal lymph node) and the lumbar lymph node (LLN) was measured at different time points after intradermal and intratumoral injection, respectively, in normal and murine mammary cancer (M2)-bearing mice.

The results were:

· ^99mTc-HSAC uptake in the SLN was significantly higher than LLN uptake.

· ^99mTc-SC showed high uptake in the SLN but also high accumulation in the LLN.

· Uptake of ^99mTc-DX was low in both the SLN and the LLN. Intradermal administration of the radiopharmaceuticals was superior to intratumoral injection.

In summary, we can conclude:

· ^99mTc-HSAC exhibited the highest uptake in the SLN, combined with the smallest amounts of

radiopharmaceutical passing through to the

· LLN.Therefore, according to the authors (Edeira et al. 2001), ^99mTc-HSAC appears to be the best radiopharmaceutical for sentinel node detection.

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