Pigmented perivascular epithelioid cell tumor (PEComa) of the kidney: a case report and review of the literature

Abstract

Heavily pigmented perivascular epithelioid cell tumors (PEComa) are rare, only eight cases of which have been reported. Unlike typical epithelioid angiomyolipoma, most of these tumors have been encountered in female patients without tuberous sclerosis. The long-term prognosis thereof is undetermined. Cytological similarity and heavy melanin pigment make it difficult for pigmented PEComa to be differentiated from pigmented clear cell renal cell carcinoma or malignant melanoma. The immunoprofile of tumor cells, such as human melanoma black-45 expression, as well as the absence or presence of other melanocytic or epithelial markers, are helpful in determining a differential diagnosis. Here we report a case of heavily pigmented PEComa of the right kidney and review the literature describing this tumor. In this case, the immunoprofile and clinical features corresponded well to those described in the literature. Since the prognosis of such disease has not yet been established, close follow-up of this patient was recommended.

Keywords: Kidney; Perivascular epithelioid cell neoplasms; Pigmentation.

Fig. 1

(A) Abdominal computed tomography. A well-demarcated cystic tumor, 3.5 cm in diameter, on the right kidney is noted. (B) The tumor is a black-pigmented mass with cystic change and is filled with blood clots and thick brownish fluid.

Fig. 2

(A) The tumor is well demarcated from the renal parenchyma and partially encapsulated by a thick fibrous capsule. (B) The tumor is composed of sheets of large polygonal tumor cells with eosinophilic or clear cytoplasm. The brown pigments in the cytoplasm strongly reacts with Fontana-Masson stain (inset).

Fig. 3

The tumor cells strongly reacted with human melanoma black-45 monoclonal antibody.