Consistent chromosome abnormalities have been described in many pediatric solid tumors. These findings led to direct molecular investigation and a better understanding of tumor pathogenesis. Clinical correlation often produced useful prog- nostic information.
GENETICS/BASIC DEFECTS
1. Somatic mutation theory of cancer
a. Resulting from the accumulation of specific genetic changes
b. Several lines of evidence
i. Monoclonal origin of most tumors, suggesting that they derive from a single progenitor cell ii. Several tumors occurring not only sporadically
but also as familial hereditary traits
iii. Mutagenic nature of most carcinogenic agents, at least in experimental systems
iv. Acquired genetic changes in the tumor cells, many of which are detectable at the chromosome level and several of these mutations have been shown to be tumorigenic in experimental animals 2. Chromosome abnormalities in neoplastic cells
a. Technical improvement in basic cytogenetic techniques i. Use of colchicine to arrest dividing cells in metaphase and hypotonic solutions to improve spreading of the chromosomes
a) Description of the correct chromosome number in humans
b) The first specifically neoplasia-associated chromosome aberration: the Ph1 chromo- some in chronic myeloid leukemia
ii. Introduction of chromosome banding techniques a) Possible to identify individual chromosome
pairs
b) To detect and characterize even subtle rearrangements
b. Clonal chromosome aberrations in neoplasms i. Primary aberrations
a) Nonrandomly associated with particular tumor types
b) Sometimes observed as the sole karyotypic deviation
c) Thought to constitute early and essential events in carcinogenesis
d) Increased genomic instability thought to be one of the consequences of the acquisition of a primary cancer chromosome rearrangement e) Many primary aberrations affect cellular oncogenes, often fusing them with other genes to encode hybrid proteins or disrupting the normal control sequences of the oncogene, causing its inappropriate expression
ii. Secondary aberrations
a) Occurrence of new abnormalities facilitated by primary aberrations
b) Nonrandom
c) Distribution of the secondary aberrations dependent on both the primary abnormality and the tumor type in which they occur iii. Cytogenetic noise
a) Resulting from acquired instability
b) Random changes with little or no selective value
3. Mechanisms by which chromosomal aberrations arise a. Aberrations that lead to aneuploidy
i. Polyploidy ii. Aneuploidy
iii. Reciprocal translocation iv. Nonreciprocal translocation
v. Amplification (double minutes) vi. Amplification (HSR)
vii. Amplification (distributed insertions)
b. Aberrations that leave the chromosome apparently intact
i. Loss of heterozygosity (LOH) (somatic recombi- nation)
ii. Loss of heterozygosity (duplication/loss) 4. Identification of specific chromosome rearrangements in
neoplasms
a. Leukemia and lymphoma
i. Crucial for more detailed studies utilizing mole- cular genetic techniques
ii. Possible to compare cytogenetic findings with morphologic, immunologic, and clinical param- eters such as the response to therapy and survival iii. Diagnostic and prognostic implications of kary-
otyping b. Solid tumors
i. In general, more complex karyotypes observed in solid tumors
ii. Have distinct patterns of primary and secondary aberrations closely associated with histopatho- logic entities
iii. Identification of only a few genes as a conse- quence of recurrent structural rearrangements iv. Fusion of transcription factor gene with other
loci, a common feature v. Tumor suppressor genes
a) Important in solid tumors
b) Thought to encode inhibitors of unrestrained growth
c) Behave in a recessive manner at the cellular level (i.e., loss or structural disruption of both wild-type alleles is required to unleash a neoplastic phenotype)
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5. Retinoblastoma (RB)
a. A prototype tumor for understanding basic concepts in cancer genetics
b. Genetics of retinoblastoma
i. Thought to be a single gene disorder caused by mutation of the RB1 gene
ii. Sporadic, nonhereditary form in most cases a) Unilateral or unifocal retinoblastoma b) A mutation in the RB1 locus occurred later
in embryogenesis
iii. Hereditary form (1/3rd of tumors) a) Bilateral or multifocal retinoblastoma b) Predisposition inherited as an autosomal
dominant trait
c) Mutations inherited from a carrier parent in 25% of the cases
d) A new mutation occurring very early in embryogenesis in 75% of cases
e) Overall estimates of the penetrance of the trait: 85–95%
c. Retinoblastoma gene, RB1
i. The first cancer-predisposition gene to be cloned ii. Chromosome map: 13q14
iii. More than 100 different mutations reported to date a) Missense mutations
b) Nonsense mutations c) Splice-site mutations d) Small and large deletions
d. Knudson’s “two-hit hypothesis” of tumorigenesis i. In the unaffected individual, both RB1 genes are
intact and serve as guardians of the retina ii. Retinoblastoma develops as a result of two sepa-
rate mutations
iii. Sporadic tumors: two separate mutations occur- ring somatically in the same retinal cell
iv. Heritable retinoblastoma: The first mutation is germinal and the second somatic
e. Inherited form of retinoblastoma
i. Critical gene for retinoblastoma located in band 13q14, suggested by cytogenetic analyses of tumor cells and lymphocytes
ii. Homozygous loss of DNA markers from 13q14 in tumor cells from individuals with familial retinoblastoma vs heterozygous loss of these DNA markers in normal cells, suggested by molecular genetic investigations
6. Neuroblastoma (NB)
a. A malignant tumor derived from undifferentiated neural crest cells that are committed to differentiate into the sympathetic nervous system
b. Inheritance
i. Sporadic in most cases
ii. A few clustered familial cases reported indicat- ing an autosomal dominant inheritance with incomplete penetrance
c. Molecular biology
i. The amplification (i.e., increased number of DNA copies) of the oncogene MYCN (N-myc) and changes in the normal diploid chromosomal content
a) Both are correlated with disease prognosis and disease recurrence
b) The amplification can be in the form of the double minute chromosomes, which are extragenomic segments of DNA, or in homo- geneously staining chromosomal regions ii. Variable DNA content of neuroblastoma
a) Near-triploid DNA index regardless of any clinical or biologic features predicts a smaller risk of progression to higher-stage diseases b) Diploid/tetraploid index tends to predict
higher risk of progression or multiple relapses
iii. Other molecular markers (receptors for nerve growth factors) associated with neuroblastoma a) Trk A: associated with favorable neuroblas-
tomas
b) Trk B: expressed in unfavorable neuroblas- tomas
7. Wilms tumor (WT)
a. Biological pathways leading to the development of Wilms tumor
i. Complex
ii. Involvement of several genetic loci
a) Two genes on chromosome 11p; one on chromosome 11p13 (the Wilms tumor sup- pressor gene, WT1) and the other on chro- mosome 11p15 (the putative Wilms tumor suppressor gene, WT2)
b) Loci at 1p, 7p, 16q, 17p (the p53 tumor sup- pressor gene), and 19q (the putative familial Wilms tumor gene, FWT2)
b. Inheritance
i. Sporadic in majority of cases (>95%)
ii. Familial predisposition to Wilms tumor is rare, affecting only1.5% of patients with Wilms tumor
c. Association with specific genetic disorders or recog- nizable syndromes
i. WAGR syndrome
a) Large constitutional deletions of chromo- some 11p13
b) Tumor suppressor gene: WT1
c) Mechanism of gene inactivation: hemizy- gous deletion
d) Wilms tumor incidence: >30%
e) Associated features: aniridia, genitourinary abnormalities
f) Mental retardation
g) Associated aniridia: caused by deletion of the PAX6 gene in the 11p13 region in close proximity to WT1 gene
ii. Denys-Drash syndrome a) Chromosomal loss: 11p13 b) Tumor suppressor gene: WT1
c) Mechanism of gene inactivation: mutation (DNA binding domain)
d) Wilms tumor incidence: >90%
e) Associated features: pseudohermaphro- ditism, mesangeal sclerosis, renal failure
iii. Beckwith-Weidemann syndrome a) Chromosomal loss: 11p15
b) Tumor suppressor gene: (WT2/BWS?) c) Mechanism of gene inactivation: unknown d) Wilms tumor incidence: 5%
e) Associated features: organomegaly, hemi- hypertrophy, umbilical hernia, neonatal hypoglycemia, other tumors such as hepato- blastoma
iv. Perlman syndrome a) Renal dysplasia
b) Multiple congenital anomalies c) Gigantism
d) Wilms’ tumor
v. X-linked Simpson-Golabi-Behmel syndrome a) Overgrowth disorder
b) Caused by mutations in the GPC3 gene located on Xq26
c) Overlapping physical features with Beckwith- Wiedemann syndrome
d) Wilms’ tumor and other embryonal tumors 8. Primary tumors of the central nervous system
a. Primitive neuroectodermal tumors (PNETs)
i. Homozygous inactivation of the TP53 gene, a tumor-suppressor gene located in 17p, secondary to i(17p): implicated in the development of sev- eral tumor types
ii. Molecular analyses indicating the existence of a second tumor-suppressor gene, distinct from and distal to the TP53 locus that might be patho- genetically involved in a subset of primitive neu- roectodermal tumors
b. Gliomas
i. A tumor-suppressor gene in 22q implicated as an essential event in the genesis of a number of neu- rogenic neoplasms
ii. A candidate for such a role: is NF2, thought to be mutated in neurofibromatosis type 2, a domi- nantly inherited disorder predisposing for gliomas, neurinomas, and meningiomas
CLINICAL FEATURES
1. Only retinoblastoma, neuroblastoma, and Wilms tumor will be discussed here
2. Retinoblastoma
a. A rare malignant tumor arising from cells of the embryonal neural retina
b. Develops only in infants and young children
c. Unifocal retinoblastoma: presence of a single retinoblastoma
d. Multifocal retinoblastoma: presence of more than one tumor
i. Unilateral: occurrence of multiple RB tumors in one eye
ii. Bilateral: occurrence of RB tumors in both eyes iii. “Trilateral” retinoblastoma: occurrence of bilat-
eral retinoblastoma plus a pinealoma e. Presenting signs
i. White papillary reflex (leukocoria): the most common presenting sign
ii. Strabismus: the second most common presenting sign
iii. Less common signs a) Poor vision b) Orbital swelling c) Unilateral mydriasis d) Heterochromia iridis e) Glaucoma
f) Orbital cellulitis g) Uveitis
h) Hyphema or vitreous hemorrhage i) Nystagmus
f. Retinoma-associated eye lesions ranging from retinal scars to calcified phthisical eyes resulting from spon- taneous regression of retinoblastoma (include benign retinal tumors called retinocytoma or retinoma) g. Patients with germline RB1 mutations: at an increased
risk of developing tumors outside the eye i. Pinealomas
ii. Osteosarcomas iii. Soft tissue sarcomas
iv. Melanomas 3. Neuroblastoma
a. The most frequently occurring solid tumor in children b. Responsible for 8–10% of all cancers in children and
approximately 15% of all pediatric cancer deaths c. 40% of cases diagnosed in children under 1 year of
age who have a very good prognosis
d. 60% in older children and young adult who have a poor prognosis despite advanced medical and surgical management
e. Amplification of MYCN gene found in neuroblas- tomas:
i. A powerful prognostic indicator ii. Associated with:
a) Advanced stages of disease b) Rapid tumor progression c) Poor outcome
f. Clinical presentation i. Variable presentation
a) Localized disease (1/3rd to 1/4th of cases) b) Metastatic disease (2/3rd to 3/4th of cases) c) Asymptomatic in small number of patients ii. Retroperitoneal and abdominal tumors
(62–65%)
a) A palpable mass b) Abdominal pain (34%) c) Weight loss (21%) d) Anorexia
e) Vomiting
f) Symptoms related to mass effect iii. Thoracic tumors (14%)
a) Dysphagia b) Cough
c) Respiratory distress
iv. Pelvis (5%) and paraspinal tumors that compress the spinal cord
a) Urinary dysfunction b) Constipation c) Fetal incontinence
d) Lower extremity weakness v. Neck tumors
a) Horner syndrome: present in patients with lesions in the cervical or upper thoracic sympathetic ganglia (1.7%)
b) Airway distress vi. Liver metastasis
a) Hepatomegaly b) Jaundice
c) Abnormal liver function tests d) Abdominal pain
vii. Bone metastases and bone marrow involvement a) Bone pain
b) Palpable bony nodules c) Anemia
d) Purpura viii. Fever (28%)
ix. Lymph node metastases: palpable lym- phadenopathy
x. Retrobulbar and orbital metastases: periorbital ecchymoses
xi. Severe diarrhea refractory to standard treatment due to production of vasoactive intestinal peptide by tumor cells (4%)
xii. Acute cerebellar encephalopathy (2%) a) Cerebellar ataxia
b) “Dancing eyes and dancing feet syndrome”
(involuntary eye fluttering and muscle jerking)
xiii. Symptoms related to high catecholamine levels (0.2%)
a) Hypertension b) Palpitations c) Flushing d) Sweating e) Malaise
f) Headache 4. Wilms’ tumor
a. The most common kidney cancer in childhood b. Represents about 6% of all childhood cancers in the
United States c. Clinical presentation
i. Presence of an asymptomatic abdominal mass:
the most common presentation
a) Usually affects one kidney with multiple tumor foci in 8% of cases
b) Bilateral in 6% of cases
ii. Hypertension, gross hematuria, and fever observed in 5–30% of patients
iii. Hypotension, anemia, and fever in a small number of patients who have hemorrhaged into their tumor iv. Rare respiratory symptoms related to the presence of lung metastases in patients with advanced- stage disease
d. Association with congenital malformations
i. Found in 60% of the bilateral cases and 4% of the unilateral cases
ii. WAGR
iii. Denys-Drash syndrome
iv. Beckwith-Wiedemann syndrome v. Perlman syndrome
vi. Beckwith-Wiedemann syndrome
vii. X-linked Simpson-Golabi Behmel syndrome e. Likelihood of developing Wilms’ tumor in aniridia
patients
i. Aniridia patients without other anomalies: 1–2%
ii. Aniridia patients with WAGR syndrome: 25–40%
DIAGNOSTIC INVESTIGATIONS
1. Cytogenetic and molecular genetic techniques used in analyzing tumor materials from patients
a. Conventional and molecular cytogenetic techniques most commonly used
i. Metaphase cytogenetics or karyotyping (G-, Q-, and R-bandings):
a) Protein digestion and/or special dye generat- ing banding pattern specific for each chro- mosome
b) Identification of numerical and structural chromosomal anomalies
ii. Fluorescence in situ hybridization (FISH) a) A small, labeled DNA fragment used as a
probe to search for homologous target sequences in chromosome or chromatin DNA b) Identification of the presence, number of copies per cell, and localization of probe DNA c) Applicable to interphase cells
iii. Comparative genomic hybridization (CGH) a) Comparative hybridization of differentially
labeled total genomic tumor DNA and nor- mal reference DNA to normal human metaphases used as templates
b) Detection of variant DNA copy numbers at the chromosome level
c) Applicable to fresh or preserved specimens iv. Multicolor karyotyping (M-FISH, SKY)
a) Hybridization with 24 differentially labeled, chromosome-specific probes allowing the painting of every human chromosome in a distinct color
b) Detection of rearrangements involving one or more chromosomes within individual metaphase spreads
c) Accurate origin identification of all seg- ments in complex rearrangements
d) Clarification of marker chromosomes b. Other techniques
i. Flow cytometry
ii. Reverse transcriptase-polymerase chain reaction (RT-PCR)
iii. Quantitative PCR
iv. Southern blot analysis of gene rearrangements v. Loss of heterozygosity analysis (LOH) vi. Restriction landmark genome scanning vii. Representational difference analysis viii. cDNA gene expression microarrays
ix. Proteomic methods
a) Matrix Assisted Laser Desorption ionization Time of Flight (MALDI-TOF)
b) Surface Enhanced Laser Desorption Ionization Time of Flight (SELDI-TOF)
2. Cytogenetic studies in retinoblastoma
a. Cytogenetically visible changes of 13q14: infrequent in retinoblastoma
b. Deletions or unbalanced translocations leading to loss of 13q14 band (10%)
c. Monosomy 13 (10%)
d. i(6p), mostly detected as a supernumerary isochromo- some (1/3rd of cases)
e. Gain of 1q material (1/3rd of cases) f. Cytogenetic aberrations in retinoblastoma
i. Secondary to RB1 mutations
ii. More related to tumor progression than to tumor establishment
3. Other studies for retinoblastoma
a. Indirect ophthalmoscopy to examine the fundus of the eye to detect retinomas, preferably by a retinal specialist b. Imaging studies (CT, MRI, ultrasonography) to sup-
port the diagnosis and stage the tumor
c. Histopathological examination to confirm the diagnosis d. Direct DNA testing of the RB1 gene in WBC DNA
i. Identify a germline mutation in about 80% of individuals with a hereditary predisposition to retinoblastoma
ii. Probability of detection of the RB1 gene muta- tion in an index case dependent on the following:
a) Whether the tumor is unifocal or multifocal b) Whether the family history is positive or
negative
c) The sensitivity of the testing methodology 4. Cytogenetic studies in neuroblastoma
a. Identification of multiple cytogenetic abnormalities in neuroblastoma
i. Allelic losses on chromosomes 1p (particularly 1p36), 11q, 14q, 7q, 2q, 3p, and 19q
ii. Allelic gains on chromosomes 17q, 18q, 1q, 7q, and 5q
b. Hyodiploid, triploid or “near triploid”, or “near- tetraploid” in modal chromosome number
i. Majority (55%) with triploid or “near-triploid”
(a chromosome number between 58–80) ii. Remainder with “near-diploid” (35 to 57 chro-
mosomes) or “near-tetraploid” (81–103 chro- mosomes)
c. Frequent partial 1p monosomy (70–80% of cases) with most commonly deleted region being between 1p32 and 1p36
d. Gain on the long arm of chromosome 17 (17q) i. Probably the most common genetic abnormality
in neuroblastomas
ii. Occurring in approximately 75% of primary tumors iii. Most often resulting from an unbalanced translo- cation of this region to other chromosomal sites, most frequently 1p or 11q
iv. A powerful independent finding of adverse outcome
e. Deletions of the long arms of chromosomes 11 (11q) and 14 (14q)
i. Appears to be common in neuroblastomas ii. Both inversely related to MYCN amplification f. Frequent presence of extrachromosomal double
minute chromatin bodies (DMs) or homogneously staining regions (HSRs)
i. Cytogenetic evidence of gene amplification ii. Amplified region derived from the distal short
arm of chromosome 2 (2p24) that contains the MYCN proto-oncogene
5. Other studies for neuroblastoma a. Imaging studies
i. Chest radiography ii. Ultrasound iii. CT
iv. MRI
v. Radionucleotide bone scan b. Blood tests
i. Elevated urinary and serum catecholamine metabolites
a) Homovanillic acid (HVA) b) Vanillylmandelic acid (VMA) ii. Abnormal liver function tests 6. Cytogenetic studies in Wilms’ tumor
a. A near-diploid chromosome count
b. Triploid-tetraploid karyotypes in a few cases with tendency to have an anaplastic morphology
c. Numerical aberrations
i. Mainly involving gains of chromosomes a) Trisomy 12: particularly frequent
b) Followed by trisomies 8, 6, 7, 13, 20, and 17 d. Structural rearrangements
i. Involve all chromosomes except the Y chromosome ii. Recombinations of 11p (>20%)
a) Vast majority of the breakpoints assigned to 11p13 and 11p15, indicating these loci are important in sporadic Wilms tumor
b) Loss of heterozygosity studies indicating that alleles from 11p13 and 11p15 are often lost in Wilms’ tumor
iii. Loss of the long arm of chromosome 16 occurring in about 20% of Wilms’ tumors: associated with poor prognosis independent of stage or tumor histology 7. Other studies in Wilms’ tumor
a. Renal ultrasound to monitor Wilms’ tumor
b. Abdominal CT scanning to determine the tumor’s ori- gin, lymph node involvement, bilateral kidney involvement, and invasion into major vessels (e.g., inferior vena cava or liver metastases)
c. Chest radiography to detect lung metastases
d. Histopathological examination to confirm the diagnosis e. Further studies of certain patients with either Wilms
tumor or associated anomalies
i. Hemihypertrophy/Beckwith-Wiedemann syn- drome: uniparental disomy studies to evaluate constitutional or somatic alterations of 11p15 ii. WAGR syndrome: molecular evaluation of the
11p13 region if chromosomal studies do not reveal a deletion
a) Fluorescence in-situ hybridization (FISH) b) Pulsed-field electrophoresis
iii. Denys-Drash syndrome: molecular evaluation of WT1 to determine whether the patient indeed carries a constitutional mutation. If the mutation is present, family members need to be screened iv. Aniridia
a) Cytogenetic analysis and molecular evalua- tion of the WAGR region by FISH or pulsed field to rule out contiguous deletion of Pax6 and WT1
b) No further screening for Wilms tumor if Pax6 mutation is identified in isolated cases of aniridia
8. Cytogenetic studies of primary tumors of the central nerv- ous system
a. Primitive neuroectodermal tumors i. Near-diploid in most tumors
ii. I(17q): the most consistent rearrangement b. Gliomas
i. Mostly astrocytomas and ependymomas ii. No specific structural rearrangement found iii. Loss of 1p and gain of 1q found in a subset of
tumors
iv. Loss of chromosome 22 common in childhood gliomas
v. Loss of material from chromosome 22, either numeric or structural aberrations, found recur- rently in rhabdoid tumors, meningiomas, and neurinomas
9. Cytogenetic studies in hepatoblastoma
a. Trisomy 2 or duplications of part of 2q: detected in half of the cases
b. Trisomy 20
c. Duplication of 8q through either i(8q) formation or trisomy 8
10. Cytogenetic studies in sarcomas
a. Ewing sarcoma/primitive neuroectodermal tumor i. Reciprocal translocation t(11;22)(q24;q12)
a) Characteristic primary rearrangement b) Found in nearly 90% of the tumors
c) Causing a fusion of the transcription factor gene FLI1 on chromosome 11 with EWS on chromosome 22 (FLI1-EWS, a fusion tran- script). Only the chimeric gene expresses on the derivative chromosome 22 which con- tains a sequence encoding a DNA-binding domain from FLI1
ii. t(21;22)(q22;q12), ERG-EWS iii. t(7;22)(p22;q12), ETV1-EWS
iv. t(17;22)(q12;q12), E1AF-EWS v. t(2;22)(q33;q12), FEV-EWS b. Additional chromosome changes
i. Trisomy 8
ii. Der(16)t(1;16)(a10-q21;q10-13), leading to gain of 1q and loss of 16q
c. Congenital or infantile fibrosarcoma i. t(12;15)(p13;q25), ETV6-NTRK3
ii. Hyperdiploid with few or no structural rearrangements
iii. Nonrandom numerical changes
a) Trisomies 11 and 20, the most frequent changes, followed by:
b) Trisomies 17 and 8 d. Osteosarcomas
i. Highly complex karyotypes in the majority of cases
ii. Chromosome number in the triploid-tetraploid range
iii. Most common numeric aberrations involving −3,
−10, −13, and −15
iv. Structural rearrangements involving chromo- some arms 1p, 1q, 3p, 3q, 7q, 11p, 17p, and 22q v. Presence of many undefined chromosome markers e. Rhabdomyosarcoma
i. The most common soft tissue sarcoma in child- hood
ii. Alveolar subtype
a) t(2;13)(q35-37;q14), shown to juxtapose the PAX3 gene on chromosome 2 with the FKHR gene on chromosome 13, leading to the formation of a hybrid transcription factor (PAX3-FKHR)
b) Found in about 70% of the alveolar tumors c) Only occasionally described in other sub-
types
iii. Embryonal subtype: numerical changes with +2, +8, +11, and +20, found in 35–50% of cases 11. Other common, recurrent translocation in solid and soft
tissue tumors of childhood
a. Alveolar soft part sarcoma: t(X;17)((p11;q25), ASPL- TFE3
b. Inflammatory myofibroblastic tumor: 2p23 transloca- tions, ALK-TPM3
c. Desmoplastic small round cell tumor i. t(11;22)(p13;q12), WT1-EWS
ii. t(11;22)(q24;q12), FLI1-EWS, ERG-EWS d. Synovial sarcoma
i. t(X;18)(p11.23;q11.2), SSX1-SSXT ii. t(X;18)(p11.21;q11), SSX2-SSXT
e. Malignant melanoma of soft part (clear cell sarcoma):
t(12;22)(q13;q12), ATF1-EWS f. Myxoid liposarcoma
i. t(12;16)(q13;p11), CHOP-TLS(FUS) ii. t(12;22)(q13;q12), CHOP-EWS
g. Extraskeletal myxoid chondrosarcoma: t(9;22)(q22;q12), CSMF-EWS
h. Dermatofibrosarcoma protuberans and giant cell fibroblastoma: t(17;22)(q22;q13), COL1A1-PDGFB i. Lipomas: t(var;12)(var;q13-15), var, HMGI-C j. Leiomyomas: t(12;14)(q13;15), HMGI-C,?
12. Other primary chromosome changes in solid tumors a. Benign tumors
i. Meningioma and acoustic neuroma a) −22
b) 22q−
ii. Mixed tumors of salivary glands a) t(3;8)(p21;q12)
b) t(9;12)(p13-22;q13–15) iii. Colonic adenomas
a) 12q− and/or +7 b) 12q− and/or +8
iv. Cortical adenoma of the kidney (+7, +7, +17,
−Y)
b. Adenocarcinomas i. Bladder
a) i(5p) b) +7 c) −9/9q−
d) 11p−
ii. Prostate: del(10)(q24)
iii. Lungs (small cell carcinoma): del(3)(p14p23) iv. Colon
a) 12q− b) +7 c) +8 d) +12 e) 17(q11)
f) 17p−
v. Kidney: del(3)(p11p21) vi. Uterus: 1q−
vii. Ovary a) 6q−
b) t(6;14)(q21;q24) viii. Endometrium
a) Trisomy 1q b) +10
c. Embryonal and other tumors
i. Testicular (germ cell tumors): i(12p) ii. Malignant melanoma
a) Del(6)(q11q27) b) i(6p)
c) Del(1)(p11p22) d) t(1;19)(q12;q13)
iii. Mesothelioma: del(3)(p13p23) iv. Glioma:−22
13. Potential prognostic markers of neoplastic disease a. Breast cancer: allelic loss at 1p22–p31 (lymph node
metastasis and tumor size >2 cm) b. Bladder cancer
i. LOH RB (high grade/muscle invasion)
ii. Genomic alterations (2q−, 5p+, 5q−, 6q−, 8p−, 10q−, 18q−, 20q+) (higher grade)
c. Cervical carcinoma: LOH on chromosome (advanced stage)
d. Colorectal cancer
i. LOH at 18q21 or p53 expression (recurrence/
poor survival)
ii. MSI (microsatellite instability) and K-ras muta- tions in normal appearing colonic mucosa (pre- dictive of colorectal cancer)
iii. P16-hypermethylation (shorter survival in Stage T3N0M0 tumors)
e. Gastric cancer
i. LOH p53 (invasive disease)
ii. LOH of 7q (D7S95) (poor prognosis (in Stage III/IV))
f. Glioma: chromosome 22q loss (astrocytomas pro- gression)
g. Head and neck squamous cell carcinoma
i. LOH of 14q (poor outcome) ii. LOH on 2q (poor prognosis) iii. LOH on 17p (chemoresistance)
h. Melanoma: LOH in plasma (advanced stage/tumor progression)
i. Neuroblastoma
i. N-myc amplification (poor prognosis) ii. TrkA expression (good prognosis)
iii. High telomerase expression (aggressive behav- ior)
j. Neuroblastomas, 4s-: N-myc amplification, 1p deletion, 17q gains, elevated telomerase activity (poor prognosis) k. Non-small cell lung cancer
i. Allelic imbalances on 9p (poor prognosis) ii. LOH 11p (poor prognosis)
l. PNET
i. LOH of 17p (metastatic disease) ii. C-myc amplification (poor prognosis) m. Prostate cancer: LOH on 13q (advanced stage)
n. Retinoblastoma: LOH at RB1 locus (tumoral differ- entiation, absence of choroidal invasion)
GENETIC COUNSELING
1. Recurrence risk a. Retinoblastoma
i. Predisposition to retinoblastoma which is caused by germline mutations in the RB1 gene: trans- mitted in an autosomal dominant fashion ii. Use RB1 mutation analysis to clarify the genetic
status of at-risk sibs and offspring when a previ- ously characterized germline cancer-predispos- ing mutation is available
iii. Use indirect testing using polymorphic loci linked to the RB1 gene in some families to clarify genetic status of at-risk family members if RB1 direct DNA testing is not available or is uninformative
iv. Use empiric recurrence risk estimates in all families in which direct DNA testing of RB1 and linkage analysis are unavailable or uninfor- mative
v. Risk to patient’s siblings
a) When there is an existing family history: a 45% chance for siblings of bilaterally affected cases and a 30% chance for siblings of uni- laterally affected cases to develop disease b) When there is absence of any family history:
2% risk for siblings of bilaterally affected cases and 1% for siblings of unilaterally affected cases to develop disease
c) There is an additional risk to siblings in the absence of any family history or documented mutation in parental leukocyte DNA because of germline mosaicism. If neither parent has the cancer-predisposing RB1 germline†mutation that was identified in the index case, germline mosaicism in one par- ent is possible and the risk to each sib of having retinoblastoma is 3–5%
d) If the index case has mosaicism for an RB1 cancer-predisposing mutation (the muta- tion arose as a post-zygotic event) and that neither parent has an RB1 germline muta- tion, the risk to the sibs is not increased and thus it is not warranted to test the sibs for the RB1 mutation identified in the index case
vi. Risk for patient’s offspring
a) About 45% by the age 6 years (consistent with an autosomal dominant inheritance with 90% penetrance) for the offsprings of survivors of hereditary (multifocal, bilateral) retinoblastoma
b) About 2.5% for the offsprings of survivors of unilateral retinoblastoma
c) The low (~1%), but not negligible, risk to the offspring of index cases with unifocal disease and a negative family history reflects the possibility of a germline RB1 mutation with low penetrance or mutational mosaicism
b. Neuroblastoma
i. Risk for patient’s sibling: low unless a parent has hereditary form of neuroblastoma
ii. Risk for patient’s offspring: 50%
c. Wilms’ tumor
i. Risk for patient’s sibling: low unless a parent has hereditary form of Wilms tumor
ii. Risk for patient’s offspring: 50%
2. Prenatal diagnosis a. Retinoblastoma
i. Prenatal testing possible if the germline RB1 mutation in the parent is known or if RB1 link- age analysis is informative in the family ii. Mutation analysis on fetal DNA obtained from
amniocentesis or CVS
iii. Use prenatal ultrasonography to detect intraocu- lar tumors if the disease-causing RB1 mutation is identified in the fetus
b. Adrenal neuroblastoma
i. Prenatal diagnosis adrenal neuroblastoma by ultrasonography usually made in the 3rd trimester ii. Sonographic appearance of the adrenal neurob-
lastoma varies a) Solid
b) Purely cystic (50%)
c) Mixed echo pattern (related to necrosis, hem- orrhage or spontaneous tumoral involution) d) Fetal hydrops
e) Hydropic placenta with metastases in the placenta
iii. Frequently producing catecholamines and hence maternal symptoms could aid the diagnosis iv. Elevated catecholamines in the amniotic fluid c. Wilms tumor by prenatal ultrasonography
i. A solid echogenic mass with a clearly defined capsule
ii. Areas of hemorrhage and necrosis may be seen within the mass
3. Management
a. Surgeries for most solid tumors
b. Determining the genetic changes present in the tumor of an individual patient: becoming increasingly important for managing the oncology patient c. Retinoblastoma
i. Goals of treatment: preservation of sight and life ii. Treatment options
a) Enucleation b) Cryotherapy c) Photocoagulation d) Photochemistry
e) External-beam radiation
f) Radiation therapy using episcleral plaques iii. Novel treatment options: systemic chemotherapy
combined with local therapy
iv. Frequent postoperative follow-up examinations for early detection of new intraocular tumors v. Detection of second nonocular tumors
vi. Individuals warrant surveillance for early mani- festations of retinoblastoma
a) Individuals with retinomas b) Asymptomatic at-risk children d. Neuroblastoma
i. Localized, low-risk disease:
a) Primary curative surgery
b) Minimal therapy: low-dose radiation or chemotherapy
c) Supportive care with surveillance
ii. Intermediate-risk patients: combination therapy with radiation, chemotherapy, and surgery iii. High-risk patients
a) Combination of radiation, myeloablative chemotherapy, and surgery (delayed) b) Autologous bone marrow transplant c) Research protocols
e. Wilms tumor: the usual approach in most patients is nephrectomy followed by chemotherapy with or with- out postoperative radiotherapy
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Fig. 1. Notice white firm neoplasm (retinoblastoma) filling the vitre- ous space of the eye.
Fig. 2. Large well circumscribed ovoid Wilms tumor in the upper pole of the kidney. Barely identifiable small areas of hemorrhage and necrosis are present.
Fig. 3. Karyotype of a patient with Wilms tumor showing 46,XY, der(11)(p11.2q13.5)del(11)(p13p15.1).
Fig. 4. Note a lobulated meningioma encroaching the brain at the inferior surface of left frontal lobe.
Fig. 7. N-MYC amplification in a patient with neuroblastoma. Gross copy number of the orange signal is noted (LSIÆ N-MYC (2p24.1) SpectrumOrange TM probe).
Fig. 5. Karyotypes of two patients with meningioma showing 46,XX,del(22)(q12) (the first picture) and 44,XX,del(7)(q32q36),
−11,der(14)t(11;14)(q12;p11),−22 (the second picture) respectively.
Fig. 6. Neuroblastoma smear. Note the anaplastic neuroblastic cells mixed with blood.
