CARCINOMA-LIKE MONOTYPIC EPITHELIOID ANGIOMYOLIPOMA IN PATIENTS WITHOUT EVIDENCE OF TUBEROUS SCLEROSIS - A CLINICOPATHOLOGICAL AND GENETIC-STUDY

We report the clinicopathologic, immunohistochemical, ultrastructural, and genetic features of an unusual renal tumor composed of large, aty pical, densely packed, clear/eosinophilic epithelioid cells. Three pat ients, two men and one woman (ages 31, 36, and 60 years of age, respec tively), had abdominal pain. Morphologically, all cases showed aggress ive features (largeness, atypical cells, sarcomatoid features, necrosi s, and, in one case, invasion of the renal vein). Despite the marked m orphologic resemblance of these tumors to high-grade sarcomatoid renal cell carcinoma, their phenotype (HMB45(+), CD68(+/-), actin(+/-), and vimentin and keratin negative) is in contrast to that observed in epi thelial tumors and parallels the phenotypic profile of angiomyolipoma. Ultrastructural analysis showed the presence of glycogen, mitochondri a, and prominent electron-dense, membrane-bound granules in the neopla stic cells, and the absence of melanosomes or premelanosomes. Genetic study, performed using polymerase chain reaction from paraffin section s, showed a loss of heterozygosity at the TSC2-containing region on 16 p in one case, and on 3p in two cases, showing that multiple genetic a lterations are taking place in these tumors. Follow-up has shown local recurrence in one case after 6 years, and the patient died I year lat er of cardiorespiratory failure. The other two patients are well after 26 and 10 months. All three patients were evaluated for signs of tube rous sclerosis, and findings were negative. We suggest that these tumo rs should be considered close relatives of the angiomyolipoma variants , composed purely of perivascular epithelioid cells. More cases and lo nger follow-up durations are needed to fully evaluate its prognostic i mplication.