Metastatic Melanoma
Lessons From the Friday Unknowns
The patient has a history of invasive melanoma on the scalp, Clark level IV, Breslow thickness was 2.5 cm.
Histologic sections of this lymph node specimen show a malignant neoplasm that fills the interfollicular and paracortical regions of lymph node.
The neoplasm is composed of large cells with highly folded nuclear contours and abundant eosinophilic cytoplasm. Some cells have prominent nucleoli. Mitotic figures are identified. The uninvolved areas of the lymph node show follicular hyperplasia.
The neoplastic cells are strongly positive for SOX10, S100 protein and vimentin, weakly positive for factor XIII, and are negative for CD1a, CD23, CD30, CD45 and CD68 (reactive histocytes are positive), pan-melanoma, Melan A, MITF, HMB45, keratins (AE!/AE3, CK903, CAM5.2), EMA, p63, p40, CEA, GFAP, p53, calretinin, and smooth muscle actin. The antibody specific for Ki-67 highlts 10–20% of the neoplastic cells.