Distinct cytologic features of spindle cell lipoma. A cytologic-histologic study with clinical, radiologic, electron...

Spindle cell lipoma (SCL) is a relatively uncommon, benign tumor that usually presents in the subcutaneous fat of adult men. Although some studies have addressed the histologic findings of SCL, only a few descriptions of aspiration cytology findings have been published. The cytologic features are poorly defined, and aspirates from SCL may cause diagnostic problems, because SCL shares some features with other fatty/spindle cell or myxoid lesions, benign as well as malignant.

Twelve patients underwent fine-needle aspiration (FNA) cytology as the primary diagnostic modality before surgery. FNA findings were evaluated and correlated with histologic features. In addition, radiologic, electron microscopic, and cytogenetic findings were analyzed. The objective of this study was to determine cytologic criteria of SCL by reviewing cytologic specimens in 12 patients with SCL who underwent FNA cytology.

All of the tumors arose in adults, and 10 tumors developed in the subcutaneous tissue of the neck, back, or shoulder girdle. Two patients presented with tumors in atypical locations; one in the tongue and one in the cheek. Cytologically, all 12 tumors were characterized by a mixture of mature adipocytes, uniform spindle cells, and collagen bundles and/or fibers in varying proportions. The presence of a myxoid matrix and of mast cells was less specific and occurred in six aspirates.

SCL has a characteristic cytologic appearance that, together with clinical data, helps to exclude low-grade liposarcoma as well as other spindle cell and myxoid lesions.