Small cell variant of chromophobe renal cell carcinoma: Clinicopathologic, and molecular-genetic analysis of 10 cases.

Abstract

Chromophobe renal cell carcinoma (CHRCC) is known for morphologic variability. Besides classic morphology, several other patterns like pigmented adenomatoid, multicystic, even papillary were documented. 10 cases of CHRCC composed of small cell population in various percentages that were analysed using morphologic parameters, immunohistochemistry and next generation sequencing. Patients were 5 males and 5 females with 40-78 age range. Size of tumors ranged from 2.2 cm to 11 cm (mean 5.17 cm). Small cell component comprised 10-80% of total tumor volume, the rest was formed by cells with classic morphology. Immunohistochemical profile followed typical CHRCC immunophenotype with positivity for CD117, CK7 among others. Neuroendocrine markers were negative. Mutations of 13 genes were found: DCIER1, FGFR3, JAK3, SUFO, FAM46C, FANCG, MET, PLCG2, APC, POLE, EPICAM, MUTYH, AR. However, only mutation of PLCG2 is listed as pathogenic. Recognition of small cell variant of CHRCC is not problematic in tumors, where “classic” CHRCC component is present. In limited material, like core biopsy, recognising this pattern could be troublesome.  Very problematic might be in limited material like core biopsy. From our limited data it seems, that small cell morphology has no influence on prognosis.