Use of cytological samples of metastatic melanoma for ancillary studies.

OBJECTIVE: Fine needle aspiration (FNA) is widely used in the diagnosis of metastatic melanoma, both at initial presentation and in the setting of recurrent disease. The purpose of this study was to evaluate the performance of confirmatory immunohistochemistry (IHC) and molecular analysis of the BRAF mutation in cytological preparations of metastatic melanoma.

METHODS: A 2-year retrospective review of pathology reports was performed on cytological samples of metastatic melanoma at the University Health Network (Toronto, Canada) and the Santa Casa Medical School (Sao Paulo, Brazil). IHC was performed on cell block sections prepared from formalin-fixed, fresh samples or residuum of CytoLyt/PreservCyt post-fixed in formalin. BRAF V600E/K mutations were assessed by amplification refractory mutation system (ARMS) analysis.

RESULTS: A total of 104 samples (94 FNAs and 10 fluids) from 83 patients (20 women, 63 men) were included. IHC was attempted in 43 cases (41.3%) and successful in 41 (95.3%). The panel number of antibodies ranged from 1 to 15 (median 3). The most frequently used melanoma markers included HMB-45, melanoma cocktail and S100 protein, used in 25 (58.1%), 23 (53.5%) and 18 samples (41.9%). Thirty cases (69.8%) used three or fewer markers. The BRAF V600E/K mutation was tested in eight samples, being successful in seven (87.5%) and positive in three (37.5%).

CONCLUSIONS: Cytological samples are a reliable and sufficient source for IHC and subsequent molecular analysis, allowing a reduced diagnostic time and rapid, appropriate treatment options in patients with advanced melanoma.