Lesson of the Month - Progesterone receptor reactivity in renal oncocytoma and chromophobe renal cell carcinoma

Aims: To investigate the reactivity for oestrogen and progesterone receptors (ER and PR) in renal oncocytoma (RO) and chromophobe renal cell carcinoma (CHRCC). Materials and methods: Thirty-eight RO, 25 CHRCC, 20 papillary RCC with oncocytic cytoplasm and 10 clear cell RCC with dominant eosinophilic cytoplasm were submitted for immunohistochemistry for ER, PR, CD117 and RCC. Results: All cases of RO and CHRCC displayed moderately positive reactivity for PR. The nuclear reactivity ranged from 60% to 90% in RO and from occasional cells to 70% in CHRCC. In CHRCC, reactivity tended to be more prevalent in areas of tumour cells with eosinophilic cytoplasm. Progesterone reactivity was focal in areas. All RO and most CHRCC were reactive for CD117 and neither RO nor CHRCC was reactive for RCC. CD117 reactivity tended to be more intense in CHRCC than in RO. Negative reactivity for CD117 and positive reactivity for RCC were observed in almost all RCC, as reported in the literature. Conclusions: PR can be used in combination with CD117 and RCC in the differential diagnosis of RO and eosinophilic variant of CHRCC with other RCC with oncocytic or eosinophilic cytoplasm.