CHROMOPHOBE RENAL-CELL CARCINOMA - CLINICOPATHOLOGICAL STUDY OF 7 CASES

Chromophobe renal cell carcinoma (CRCC) may be grossly and microscopic ally confused with oncocytoma. It is now believed that many, if not al l, of the so-called malignant oncocytomas OF oncocytomas with metastas es reported in the literature were indeed chromophobe renal cell carci nomas. CRCC is characteristically positive for colloidal iron and show s cytoplasmic microvesicles in electron microscopy. This study of CRCC is thought to be the first one done in Latin America. Of a total of 1 06 renal epithelial neoplasms, 7 (6.6%) fulfilled the criteria for chr omophobe renal cell carcinoma. This frequency in Brazil is similar to that in other parts of the world. There was no difference in age, sex, and race distribution of CRCC compared to usual renal epithelial tumo rs. Grossly, the CRCC ranged in size from 3.5 to 20 cm (average: 10.2 cm) in greatest dimension. Most frequently, the tumor was brown on the cut surface. The growth pattern showed compact areas in all tumors an d, in most of the cases, both clear and eosinophilic cellular subtypes were seen. The electron microscopic findings favor an origin of the m icrovesicles from outpouchings of the outer membrane of mitochondria. The strong positivity for colloidal iron in spite of the destruction o f the cytoplasmic vesicles in paraffin-embedded specimens seems to ind icate that the acid mucopolysaccharides are not located inside the mic rovesicles. By the time of diagnosis, only one case had regional lymph node metastases and this particular case was the only one mixed (asso ciated with the usual renal cell carcinoma). The follow-up examination after nephrectomy showed that prognosis seems to be favorable in CRCC , except when the tumor coexists with the usual renal cell carcinoma.