Fine needle aspiration cytology smear patterns of malignant melanoma.

The 23 cases of malignant melanoma diagnosed by fine needle aspiration (FNA) cytology from the years 1974 to 1983 were reviewed. The smears showed an abundance of melanin pigment overshadowing the tumor cells in six cases, a pleomorphic cytology in six, a round-cell morphology in four, an epithelial-like appearance in six and a spindle-cell pattern in one. Melanin pigment was readily seen in the May-Grünwald-Giemsa-stained smears in all cases except two, in one of which it was apparent after use of the Schmorl stain for melanin. An interesting observation was the presence of multiple, well-defined clear vacuoles in the cytoplasm of many cells and similar nuclear vacuolization in some cells in smears from ten cases. These cells could be regarded as intermediate forms between the nonvacuolated cells and the hypervacuolated balloon cells. The cause of this vacuolization is probably the result of degeneration and coalescence of melanosomes due to abnormal melanogenesis. These vacuoles were prominent in May-Grünwald-Giemsa-stained smears but were only faintly visible in Papanicolaou-stained smears, which may be the reason why this observation had not received emphasis in earlier reports of the FNA cytologic diagnosis of melanoma, in which the Papanicolaou stain was primarily used.