Myxoid liposarcoma is the most common type of liposarcoma. The magnetic resonance imaging (MRI) features of this tumor were evaluated and correlated with its clinical and histological features in seven patients to determine under what circumstances the tumor should be considered in differential diagnosis and why its signal intensity differs from those of lipoma and lipoma-like (lipoblastic) liposarcoma. In all patients the tumor presented in a lower extremity (5 thigh, 2 calf) as a painless, slowly growing mass which had been present for several months to several years. MRI examination revealed the tumors to be encapsulated, noninfiltrating, and usually septated. On T1-weighted sequences five of seven lesions (71%) showed lacy, amorphous, or linear foci of high signal within a low signal mass. These foci are believed to represent fat within the tumor and distinguish it from several other benign and malignant masses. If an indolent mass in a lower extremity demonstrates a predominantly low signal with a few amorphous or linear high signal foci on T1-weighted sequences, one should consider the possibility of myxoid liposarcoma even if it appears benign by all other criteria. Histologic evaluation showed that myxoid liposarcomas contain less than 10% mature fat, which accounts for their low signal on T1-weighted sequences in contrast to the high signal of lipomas and lipoblastic liposarcomas.

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.

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