Abstract
Background : Perivascular epithelioid tumor (PEComa) is a recently recognized disease entity and includes angiomyolipomas, lymphangioleiomyomatosis, clear cell sugar tumors, and related lesions (PEComa family). They occur in the kidney, lung, hepatobiliary tract, pancreas, genitourinary organs, breast, bone, and soft tissues. Although most of them are benign, rare cases follow an aggressive course.
Case : We present herein on a case of malignant PEComa, which synthesized a large amount of melanin, occurred in the retroperitoneum of a 23-year-old female. Touched smear cytology of the resected tumor showed a large amount of discohesive clusters of epithelioid cells and isolated epithelioid cells against a background of necrotic debris. The cells had highly atypical nuclei and a relatively large and clear cytoplasm, reminiscent of renal clear cell carcinoma. Some of them showed nuclear pseudoinclusion and cytoplasmic melanin granules. Histological examination showed a nested or sheet-like structure composed of highly atypical cells with polygonal and clear cytoplasm, massive necrotic foci, and vascular involvement. The tumor cells were immunoreactive for gp100 (HMB-45) and PgR, but immunonegative for CK (AE1/AE3), EMA, SMA, vimentin, and S100. These results indicated the tumor was a malignant PEComa.
Conclusion : When encountering cytological specimens with these characteristics, PEComa should be listed as a differential diagnosis.
