Lipid‐rich metastatic balloon‐cell melanoma: Diagnosis by a multimodal approach to aspiration biopsy cytology

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Abstract
Fine needle aspirates from one of multiple liver nodules revealed a large number of discohesive malignant cells with abundant vacuolated cytoplasm. The patient had had left eye enucleation the year before, for a melanoma with focal areas of clear cell change. Pap stained preparations from the liver FNA displayed well the nuclear features of balloon cell melanoma, including anisonucleosis, prominent nucleoli and intranuclear inclusions. Diff‐Quik stain demonstrated best the cytoplasmic features such as distinct cell margins and finely dispersed and sharply delineated clear vacuoles. No pigmentation was noted but melanoma was suspected after the history prompted comparison with the enucleated specimen resected a year previously. A multimodal battery of ancillary methods including electron microscopy (EM) and immunocytochemistry (ICC) allowed the confirmation of balloon‐cell melanoma, a rare variant not previously described in the eye. By EM, abundant lipids were identified along with melanin‐containing structures resembling melanosomes. S‐100 positivity along with negativity for epithelial, lymphohistiocyte and germ cell markers was compatible with melanoma, These findings are consistent with the view that cytologic detection of poorly cohesive, hypervacuolated cells does not exclude the possibility of melanoma. This rare example of a lipid‐containing melanoma stresses the value of obtaining good clinical history, comparing FNAs to any pre‐existing material and utilizing a multimodal approach to cytologic diagnosis in select cases.