History
69-year-old female with a history of melanoma of the right heel. After several recur- rences, the patient underwent right inguinal lymph node biopsy with three of seven positive nodes. More recently, she underwent resection of three lesions in the right leg, anterior shin, lateral leg, and foot. The current exam is being done for staging.
Findings
The exam of the lower extremities reveals focal hypermetabolism in the subcutaneous soft tissues of the right lateral foot (Figure 19.1.1). There is a second focus in the dorsum of the right midfoot. There is subcutaneous focal disease in the lateral soft tissues of the right lower leg above the ankle. There is also moderate hypermetabo- lism in the deep subcutaneous tissues adjacent to the tibia (Figures 19.1.2 and 19.1.3) at the junction of its proximal middle third anterolaterally, more on the lateral than the medial side. On the contralateral left foot, there is a focus at the left plantar fore- foot which is probably urine contamination. Increased synovial activity at the left knee probably represents synovitis. There is intense hypermetabolism in multiple areas in the anterior left thigh (Figure 19.1.4) and left lateral gluteal soft tissues (Figure 19.1.5).
These correspond to reticular changes in the subcutaneous fat on CT. The findings are suspicious for cellulitis and could be related to injection.
In the whole body exam (Figure 19.1.6), there is intense hypermetabolism corre- sponding to confluent right external iliac adenopathy, similar to that reported on recent CT. There is prominent gastric activity but this is presumed physiologic. A small nodular lesion is noted on the CT in the right lower lung which is negative by PET scintigraphy and has the appearance of a small AVM on CT. There is no evidence for skeletal or pulmonary metastasis or hepatic metastasis.
Impression
1. There are multiple areas in the right lower extremity which appear subcutaneous in location and are fairly intensely hypermetabolic, consistent with metastatic disease: right lateral foot; right dorsal midfoot; right lateral lower leg above the ankle;
and right shin in the tissues around the tibia at the junction of the proximal and middle third.
2. Intensely hypermetabolic pathologic confluent right external iliac adenopathy.
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Case 19.1
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3. Reticular changes in the fat with hypermetabolism of the left thigh and lateral gluteal subcutaneous soft tissues, likely cellulitis and possibly related to injections.
4. 18-FDG PET negative right lower lobe pulmonary finding, probably an AVM.
5. Negative for skeletal, hepatic, or pulmonary metastasis.
Pearls and Pitfalls
• Breslow thickness is a good indicator for recurrence and prognosis.
• Lymphoscintigraphy and sentinel node biopsy have a sensitivity of 94% and speci- ficity of 100% for the detection of occult regional metastases.3,5,6
FIGURE19.1.1.
FIGURE19.1.2. FIGURE19.1.3.
FIGURE19.1.6.
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• PET is currently used for extranodal staging, restaging, and recurrent melanoma.7,9,10
• The sensitivity of PET for skin metastases less than 3 mm in diameter is 79% and the specificity is 86%.1,8,10
Discussion
Malignant melanomas are cutaneous tumors which develop from melanocytes.
Melanoma can involve the eye, central nervous system, respiratory, gastrointestinal, and genitourinary tracts. It is now the fifth most common tumor and second to lung cancer for mortality. Ninety percent of malignant melanoma is curable if discovered early. The overall cure rate is 80%.
History
75-year-old male who has a history of malignant melanoma twenty years ago. A CT demonstrated new multifocal metastases in the right posterior 6th rib, liver, and lungs bilaterally. Evaluation of extent of disease is requested.
Findings
There is a focus of sternal hyperactivity associated with a soft tissue component and bony destruction in comparison with the CT. A rib lesion on the left upper lateral chest wall is noted (Figures 19.2.1 and 19.2.2). A right anterior lateral rib is also involved.
The posterior elements in a left upper thoracic spine are involved with metastatic deposits with activity seen on the right projecting to the pleural surface. The T-7 vertebral body displays a lytic lesion with a soft tissue mass possibly compressing the spinal cord (Figure 19.2.3). Another smaller vertebral lesion at the level of T-12 on the right is also seen. There is a large destructive lesion associate with soft tissue mass in the posterior aspect of the right ilium. Multiple sites of hypermetabolism are noted on the medial aspect of the right lobe of the liver extending from the dome to the caudate lobe, representing multiple coalescing nodules corresponding to the abnor- malities described on the earlier CT (Figure 19.2.4). The activity in the shoulders bilaterally, right greater than left, is likely inflammatory arthritis. There is mild focal
Case 19.2
FIGURE19.2.1.
FIGURE19.2.4.
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patchy ill-defined activity on the right lateral thigh which may represent local skin inflammation.
Impression
1. Multiple bony metastasis as described above, in particular the vertebral body at the level of T-7 with a soft tissue mass which may be compressing the spinal cord.
2. Multifocal sites hypermetabolism in the right lobe of the liver consistent with metastatic disease.
3. Ill-defined right lateral thigh uptake, likely inflammatory in nature.
Pearls and Pitfalls
• PET-CT is very helpful in identifying spinal cord or nerve root compression sec- ondary to metastatic disease.2,9,10
• FDG PET alters clinical management in up to 50% of the patients with melanoma.7,9
Discussion
The highest prevalence of disease is in young females between the ages of 25 and 29, with the age range of 15 to 39. Red-haired, blond, light-skinned individuals, sun expo- sure, race, nevus, family history, and xeroderma pigmentosum are other risk factors.
There are 4 major subtypes of malignant melanoma: the lentigo maligna melanoma (4%–15%), superficial spreading melanoma (70%), nodular melanoma (12%–30%), and acral lentiginous melanoma (2%–8%). Staging is based on the TNM classification system which requires histologic correlation of (T stage) and depth and level of inva- sion as described by Breslow and Clark.
History
75-year-old female who has stage-III melanoma. The original resection was from the toe. She is status post ipsilateral right inguinal lymph node dissection. The current examination is for restaging.
Findings
There is a single pathologic hypermetabolic focus corresponding to a normal-to- borderline size deep left axillary lymph node (Figure 19.3.1), near the chest wall, which is measured on the CT at 1 cm ¥ 2cm. This is a solitary hypermetabolic focus. It is con- sistent with a solitary axillary lymph node metastasis. The right inguinal area is weakly positive (Figure 19.3.2), consistent with recent (5-month) scar. The lower extremities are negative with notation of muscular activity in the right medial calf (Figure 19.3.3).
No hepatic lesion or pulmonary lesion is apparent.
Case 19.3
FIGURE19.3.3.
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Impression
1. Apparently solitary hypermetabolic focus corresponding to a deep left axillary lymph node near the chest wall, measuring 1 cm ¥ 2cm. No other evidence for metas- tasis is evident by PET scintigraphy, inclusive of the liver and lungs.
2. Weak activity corresponding to the right inguinal scar, consistent with recent scar formation.
3. Right medial calf muscular activity. No pathologic significance is attributed to this finding.
Pearls and Pitfalls
• 3% to 5% of patients presenting with malignant melanoma will develop a second primary melanoma within 3 years of treatment.1,3,4
• PET is a useful tool for evaluating recurrent or metastatic disease in patients with Stage III and IV disease.4,10
• Sentinel node biopsy has a sensitivity of 95% for initial melanoma staging.6
Discussion
Early surgical resection is the mainstay of treatment. This is followed by sentinal node mapping with either blue dye or technetium-labeled ultrafiltered sulfur colloid or both.
If the nodal basin is positive for cancerous cells, radical lymph node dissection may be necessary. PET is more accurate than regional lymph node staging and is used for sys- tematic staging of disease.
