Pediatric melanoma and aggressive Spitz tumors: a retrospective diagnostic, exposure and outcome analysis.

BACKGROUND: The diagnosis and management of pediatric melanomas is challenging given the presence of both melanomas and histologically aggressive Spitz tumors of undetermined biological significance (S-UBS) in this age group. Study objectives were to examine: factors leading to diagnostic delays, therapy side effects and patient outcomes in these diagnostic groups. METHODS: A retrospective case review was performed using The University of Michigan's pediatric oncology database over a 13-year timespan. Patients referred to our clinic for consideration of interferon therapy due to a diagnosis of a stage III melanoma or aggressive appearing S-UBS with significant lymph node involvement were included. RESULTS: We found two major causes of diagnosis delay: patients with amelanotic lesions misdiagnosed as having a wart and cases reviewed by non-expert pathologists upfront. The side effects from interferon therapy requiring dose adjustments included neutropenia, thrombocytopenia and mood disturbances. There was wide variability in surveillance scan utilization, therefore leading to variability in patient radiation exposure. Unlike melanoma patients, none of the S-UBS patients experienced disease progression or death. CONCLUSIONS: This study highlights the challenges with the initial clinical diagnosis and pathological sub-categorization of the pediatric S-UBS/melanoma spectrum of skin lesions and emphasizes the role of expert pathology review upfront. Further, education at the primary care level could improve accurate and timely diagnoses. Earlier diagnosis could spare patients from more extensive interventions, metastatic spread or adverse outcomes in this patient population. This study is limited due to its retrospective, single-institution perspective.

What is a sentinel node? Re-evaluating the 10% rule for sentinel lymph node biopsy in melanoma.

INTRODUCTION: Many surgeons use the "10% rule" to define whether a lymph node is a sentinel node (SLN) when staging malignant melanoma. However, this increases the number of SLN removed and the time and cost of the procedure. We examined the impact of raising this threshold on the accuracy of the procedure. METHODS: We reviewed the records of 561 patients with melanoma (624 basins) who underwent SLN with technetium Tc99 labeled sulfur colloid using a definition of a SLN as 10% of that of the node with the highest counts per minute (CPM). RESULTS: Of the 624 basins, 154 (25%) were positive for metastases. An average of 1.9 nodes per basin were removed (range 1-6). Metastases were found in the hottest node in 137 cases (89% of positive basins, 97% of basins overall). Increasing the threshold above 10% decreased the number of nodes excised and the costs involved, but incrementally raised the number of false negative cases above baseline (a 4% increase for a "20% rule," 5% for a "30% rule," 6% for a "40% rule," and 7% for a "50% rule"). Taking only the hottest node would raise the false negative rate by 11%. CONCLUSIONS: Although using thresholds higher than 10% for the definition of a SLN will minimize the extent of surgery and decrease the costs associated with the procedure, it will compromise the accuracy of the procedure and is not recommended.

Low CD7 expression in benign and malignant cutaneous lymphocytic infiltrates: experience with an antibody reactive with paraffin-embedded tissue.

Loss of CD7 expression by neoplastic lymphocytes is considered a distinguishing characteristic of mycosis fungoides (MF) and cutaneous T-cell lymphoma. Reports to date examining for the CD7 immunophenotype in MF have been performed on fresh-frozen tissue. In this study, we used a paraffin-reactive antibody directed against CD7 to determine its range of expression in MF and to compare these results with those in controls. Examining 22 cases of MF and 61 controls, we found minimal CD7 expression by lymphocytes in MF and in a few cases of benign inflammatory dermatosis (BID). The lowest mean CD7 counts (as a percentage of total lymphocytes) were found in MF (patch stage: 5% +/- 5%, range: 0-10; plaque and tumor stages: 15% +/- 5%, range: 5-25), and these counts were significantly lower than those for BID (35% +/- 20%, range: 5-80; p = 0.001). By logistic regression analysis, low CD7 expression (<10% lymphocytes labeling) had sensitivity and positive predictive values of 80% and 72%, respectively, and specificity and negative predictive values of 93% and 96%, respectively, for the diagnosis of patch stage MF. False-positive results were found for spongiotic dermatitis. Moreover, spongiotic dermatitides exhibited a progressive decrease in mean CD7 counts from acute to subacute to chronic stages (50% versus 35% versus 30%, respectively). In conclusion, minimal CD7 expression is a specific finding for MF. Benign inflammatory infiltrates can also show low CD7 expression, however, which rarely matches that of patch stage MF. Progressive loss of CD7 expression in BID is the likely consequence of expansion of antigen-selected CD3+CD4+CD7- T cells. These inflammatory CD4+CD7- T cells may represent the physiologic counterpart to the neoplastic lymphocyte of MF.