[515] Reticulin and NM23 Staining in the Interpretation of Lymph Nodal Nevus Rests

WA Kanner, CI Barry, CN Smart, DP Frishberg, SW Binder, MR Wick. University of Virginia Health System, Charlottesville, VA; Cedars-Sinai Medical Center, Los Angeles, CA; UCLA, Los Angeles, CA

Background: Melanocytic nevus rests in lymph nodes are a known diagnostic challenge, especially in patients with a history of melanoma. Reticulin and NM23 have been studied in melanocytic lesions of the skin. The pattern of reticulin staining in melanomas surrounds groups/nests of melanocytes but individual cells in benign nevi. NM23, a metastasis-suppressor gene, has an association with metastatic potential in melanomas and some carcinomas. We sought to evaluate the differential diagnostic utility of these markers in capsular nevus rests (CNR) and malignant melanoma (MM) metastatic to lymph nodes.
Design: Archival paraffin-embedded lymph nodes of 28 cases from three academic centers (14 cases of MM to lymph nodes and 14 cases of CNR, all confirmed with Melan-A staining) were stained with reticulin (DAKO kit), and NM23 (1:3000, monoclonal, Santa Cruz). In 27 cases, the patient had a history of melanoma, and in 1 the patient had a history of breast cancer. The pattern of reticulin staining was reported as surrounding groups if staining was noted around 5-10 melanocytes in greater than 50% of the lesion, but was otherwise reported as surrounding individual melanocytes. Strong cytoplasmic staining was considered to represent reactivity for NM23.
Results: Reticulin staining around groups of melanocytes was identified in all 14 cases of MM. In the majority of cases, staining was noted around large nests (>20 melanocytes). Regarding CNR cases, 12 of 14 cases (79%) demonstrated staining around individual melanocytes, while in 2 cases, reticulin surrounded melanocytic groups. NM23 staining was equivocal in all cases of MM and CNRs, with adequate labeling of controls.
Conclusions: Reticulin staining reliably invests groups of melanocytes in cases of metastatic melanoma, while in capsular nevus rests, it predominantly surrounds individual melanocytes. NM23 demonstated no discriminatory value in this analysis, in contrast to the results of prior reports. In cases in which a collection of melanocytes is present within a lymph node, reticulin deposition around individual melanocytes supports a diagnosis of capsular nevus rest.
Category: Dermatopathology

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 80, Wednesday Afternoon


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