Fine Needle Aspiration Cytology and Immunocytochemistry of Metastatic Melanoma

Abstract

The cytological and immunological findings of 81 metastatic melanomas are described. Fine needle aspiration was performed from secondary deposits in lymph nodes (38), subcutaneous and soft tissue (36), abdomen (5), lung (1) from 67 patients with histologically verified malignant melanoma. One patient had disease which had spread into the cerebrospinal fluid. Cytomorphologically the cases were classified as classical (47%), carcinoma-like (22%), spindle cell type (14%), lymphoma like (6%), undifferentiated (6%), myxoid type (3%), and clear cell type (2%). All cases were immunologically characterized using antibodies to S-100, vimentin and cytokeratin. All cases were S-100 positive and the majority (96%) reacted with antibodies to vimentin. A weak heterogenous reactivity to cytokeratin antibody was detected in only eight cases. The HMB45 antibody was applied to 20 cases and 16 (80%) of these tumours were positive. In summary, we found that an immunological characterization was necessary to conclusively diagnose over 50% of metastatic melanomas which presented with an equivocal cytological picture.

Diagnostic challenges of metastatic spindle cell melanoma on fine-needle aspiration specimens

“…The frequency of each feature in melanoma was reported to be approximately 50%. 5,7,10,12,13 We found that these features were noted less frequently in the spindle cell melanomas (22%, 35%, and 22%, respectively), and 7 of the current study cases (9%) failed to exhibit any of the characteristic features. In addition, the cells of spindle cell melanoma tended to form cohesive microtissue fragments with a fascicular or storiform arrangement.…”

“…Perry et al 5 reported that pleomorphism was more frequent in epithelioid melanoma, whereas bland nuclei and inconspicuous nucleoli were far more frequent in spindle cell melanoma. Similarly, Nasiell et al 13 found that cytoplasmic melanin pigmentation, vacuolization, nucleoli, and intranuclear pseudoinclusions were observed less frequently in spindle cell melanoma compared with conventional melanoma. FNA specimens of metastatic spindle cell melanomas aspirated from various anatomic sites could be mistaken for metastatic lesions from other neoplasms or reactive lesions with similar features, especially when a reliable clinical history is unavailable and the tumor cells are predominantly or ''purely'' spindle shaped without the characteristic features of melanoma.…”

“…The incidence of cytoplasmic pigmentation in FNA samples varies in different studies, ranging from 30% to 80%. 4,5,7,8,10,[12][13][14] In the current study, only 15% of the cases had recognizable cytoplasmic melanin. When melanin pigments were identified, they were often quite subtle and sparse and thus easily overlooked.…”

“…[4][5][6][10][11][12][13]15 However, to our knowledge, the FNA features of this variant have not been described in detail in the literature, and most have been reported as single case reports or small series. 4,5,7,12,13,16,17 The misdiagnosis of a spindle cell melanoma is not uncommon, even on histopathologic examination. 3 In the current study, we retrospectively reviewed the cytologic features and immunocytochemical findings of 81 FNA samples of metastatic spindle cell melanoma and discussed the potential diagnostic pitfalls in this setting.…”

“…[4][5][6][7][8][9][10][11][12][13][14] Characteristic cytologic features that have been reported to date are hypercellular aspirates, dispersed cellular distribution, epithelioid or plasmacytoid cells with eccentric nuclei, cytoplasmic melanin pigments, intranuclear pseudoinclusions, macronucleoli, and binucleation or multinucleation. [4][5][6][7][8][9][10][11][12][13][14] Although the majority of melanomas are easily diagnosed, melanomas with unusual cytologic features can cause a diagnostic dilemma, particularly if the cells are sampled via FNA in a metastatic setting.…”