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

Abstract

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 this context. 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. Twenty-eight cases (14 cases of metastatic melanoma to lymph nodes and 14 cases of lymph node nevus rests, all confirmed with Melan-A staining) were stained with reticulin and NM23. The pattern of reticulin staining was reported as surrounding groups if staining was noted in approximately 5-10 melanocytes in greater than 50% of the lesion but was otherwise reported as surrounding individual melanocytes. Cytoplasmic staining was considered to represent reactivity for NM23. Reticulin staining around groups of melanocytes was identified in all 14 cases of metastatic melanoma. Regarding nodal nevus rest cases, 12 of 14 cases (86%) demonstrated staining around individual melanocytes, whereas in 2 cases, reticulin surrounded melanocytic groups. NM23 staining was equivocal in all cases. Reticulin staining reliably invests groups of melanocytes in cases of metastatic melanoma, whereas in nodal nevus rests, it predominantly surrounds individual melanocytes. NM23 demonstrated no discriminatory value in this analysis. In cases in which a collection of melanocytes is present within a lymph node, reticulin deposition around individual melanocytes supports a diagnosis of lymph nodal nevus rest.

Benign melanocytic lymph node deposits in the setting of giant congenital melanocytic nevi: the large congenital nodal nevus

“…There are rare reports of melanocytic rests presenting within lymph node sinuses or parenchyma, usually with associated cortical or medullary deposits . Recently Kanner et al observed reticulin staining surrounding the individual nodal melanocytes of nodal melanocytic nevi, whereas reticulin staining in metastatic melanoma surrounds groups of cells . In our cases, reticulin stain was not helpful in distinguishing benign from malignant deposits because nodal melanocytes could not be reliably distinguished from other normal nodal structures such as vessels with this staining preparation.…”

Reticulin immunostaining revisited

“…[ 1 3 ] Recently, a reticulin immunostain was suggested as a means of distinguishing between nevi and metastatic melanoma in lymph nodes. [ 4 ] In the present study, we observed reticulin immunostaining patterns in malignant melanomas, benign intradermal nevi, and blue nevi. We also evaluated the concordance in evaluation of the pattern between observers.…”

Nevus cell aggregates massively occupying parenchyma of an external iliac lymph node: A case report and review of the literature

“…The mean age of patients with nodal nevi is around 53 years (range: 2‐84 years) 1‐3,5‐30 . Nodal nevi are most often found in SLN of melanoma and breast cancer patients; thus, they are more likely to be observed in axillary and inguinal lymph nodes 1‐3,5‐31 . In breast cancer patients, nodal nevi occur almost entirely in females.…”

“…Thus, reticulin tends to be around groups of tumor cells (5-10 cells). On the contrary, in nodal nevi, the reticulin staining is more likely to be localized to individual nevus cells 26. Recently, Vysis melanoma FISH probes targeting 6p25 (RREB1), 6q23 (MYB), 11q13 (CCND1), and CEP6 have been widely used in differential diagnosis of nevi and malignant melanomas 35.…”