Chromophobe renal cell carcinoma-like thyroid carcinoma: A novel clinicopathologic entity possibly associated with tuberous sclerosis complex.

We report three cases of chromophobe renal cell carcinoma-like thyroid carcinoma as a novel clinicopathologic entity possibly associated with tuberous sclerosis complex. A 15-year-old female, a 19-year-old male, and a 21-year-old male presented with primary thyroid carcinoma. Two of the patients had associated tuberous sclerosis complex. Macroscopically, the carcinomas showed invasive growth. Histologically, the carcinoma cells showed a trabecular pattern with thin vascular stroma, and were characterized by abundant eosinophilic cytoplasm with perinuclear clearing, a prominent cell border, a wrinkled nuclear membrane, and binucleation, which are all features of chromophobe renal cell carcinoma. Immunohistochemically, the carcinoma cells were positive for thyroglobulin, TTF1, and PAX8, and negative for CD10, calcitonin, and carcinoembryonic antigen. Vascular invasion was visible in all cases, but distant metastasis was not detected during follow-up. The original pathological diagnoses of the three cases were widely invasive follicular thyroid carcinoma, poorly differentiated thyroid carcinoma, and oxyphilic variant of papillary thyroid carcinoma. Thus, the cases were similar to chromophobe renal cell carcinoma associated with tuberous sclerosis complex as they were characterized by histologic findings consistent with chromophobe renal cell carcinoma, occurrence in an adolescent or young adult, and favorable prognosis regardless of the presence of vascular invasion and an infiltrating growth pattern resembling poorly differentiated carcinoma. The etiopathogenesis also seemed to suggest the presence of the tuberous sclerosis complex genetic abnormality.