Pediatric Primary Ovarian PEComa: Morphological Approach and Diagnostic Challenges

Perivascular epithelioid cell tumor (PEComa) is a mesenchymal neoplasm that displays markers for melanocytic and smooth muscle. Gynecological PEComas account for almost one-quarter of all PEComas, with the uterus being the most common site. Primary ovarian PEComas are rare. Most of these tumors are benign. Malignancy is reported in a small subset only. The radiology findings are variable and confusing. Histology and immunohistochemistry (IHC) are diagnostic. In the ovary, the diagnosis of this lesion becomes difficult due to the wide morphological spectrum of ovarian neoplasms ranging from germ cell to sex cord tumors. We present an index case of primary pediatric ovarian PEComa that shows overlapping features with the admixture of cells with clear and eosinophilic cytoplasm, calcification, and the presence of melanin pigment in an eight-year-old girl. Morphological differentials were yolk sac tumor, steroid cell tumor, juvenile granulosa cell tumor, metastatic renal cell carcinoma, melanoma, and clear cell carcinoma of the ovary. The tumor cells displayed diffuse expression for HMB45, focal for SMA. Vimentin, CK, S-100, calretinin, CD-10, and inhibin were consistently negative. Further TFE3 was performed at higher center which was positive, further confirming the diagnosis. The present case highlights that stepwise morphological approach, clinicoradiological correlation with the help of a limited IHC panel can diagnose even rare lesions.

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