Clear cell 'sugar' tumor of the breast: another extrapulmonary site and review of the literature.

A group of lesions show morphologic and immunophenotypic evidence of differentiation toward a putative perivascular epithelioid cell. These so-called PEComas include angiomyolipoma, lymphangiomyoma, lymphangioleiomyomatosis, renal capsuloma, clear cell myomelanocytic tumor of the falciform ligament/ligamentum teres, and clear cell "sugar" tumor. PEComas are characterized by strong immunoreactivity with the HMB45 antibody and variable expression of muscle markers. This family of lesions may be composed of a spectrum of cells from epithelioid to spindle cells with clear to granular eosinophilic cytoplasm. One member of this family, composed of epithelioid cells with glycogen-rich clear cytoplasm, is descriptively called a clear cell "sugar" tumor. This tumor, originally described in the lung, is being recognized increasingly in extrapulmonary sites. We report a case of a primary extrapulmonary clear cell "sugar" tumor occurring in the right breast of a 16-year-old girl. The tumor was composed of clear epithelioid cells with abundant glycogen and distinct cell borders. The tumor showed strong immunoreactivity with HMB45 antibody and Melan-A. There was focal vimentin staining. In addition, there was diffuse and strong nuclear staining for progesterone receptor. Antibodies to actins, S-100 protein, cytokeratins (AE1/AE3 and CAM5.2), desmin, and estrogen receptor were negative. The tumor was completely excised, and the patient is well without evidence of disease 9 months postexcision.