Renal
tumors are one of the most diverse groups of
tumors in pathology. Many emerging and important entities have been described recently. Here, we describe a series of renal
tumors occurring in adult patients, with distinct histologic features, and with a striking resemblance to gonadal
sex cord-stromal tumors. Patients were three males and three females aged 39-82 years;
tumor size ranged from 0.9 to 3.6 cm. Five
tumors were organ-confined, while one case had a focal perinephric invasion. No aggressive behavior was noted. Microscopically, all the
tumors were composed of loose or compact tubular structures with elongated or angulated shapes. The
tumor cells were cylindrical or cuboidal, with pale eosinophilic cytoplasm, irregular nuclear membranes, and ISUP/WHO grade 2-3 nuclei. The stroma showed focal or prominent
collagen deposition with prominent basement membrane-like material. In all cases, the
tumor cells were positive for PAX8, CD10, and
vimentin and retained positivity for FH and SDHB.
Cathepsin K and AMACR were variably positive.
Tumors were negative for HMB45,
Melan A, TFE3, SF1,
inhibin,
calretinin, ER, PR, CD117, OCT3/4, SALL4, ALK, and WT1. Molecular studies showed no abnormalities in TFEB, TFE3, or FH genes. In 3/4 tested cases, mutation of the NF2 gene was present. In all the tested male cases, loss of the Y chromosome was found. In the relatively short follow-up, these
tumors appear to have indolent behavior. This study expands the clinicopathologic diversity of renal cell
tumors by describing a series of potentially novel
tumors morphologically resembling gonadal sex-stromal
tumors, with negativity for sex cord-stromal markers. Potential relationship to recently described biphasic hyalinizing psammomatous
renal cell carcinoma is discussed.