Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is an autosomal dominant familial syndrome characterized by the development of cutaneous and uterine leiomyomas as well as renal tumors. The mutation of this condition has been identified in the fumarate hydratase (FH, 1q42.3-q43) gene. The histology of the renal cancers has not been well described or illustrated because of the newness of the syndrome. We reviewed 40 renal tumors resected from 38 patients belonging to HLRCC families with proven fumarate hydratase germline mutation. Patients ranged in age from 17 to 75 years of age. Tumors were unilateral in all but 2 cases. The size of the tumors varied between 2.3 and 20 cm and there was no laterality preference. Several different architectural patterns were recognized: papillary (25 cases), tubulo-papillary (8 cases), tubular (2 cases), and solid (1 case). Mixed patterns were also present in 4 cases. The most important histologic feature of these neoplasms, which we believe to be the hallmark of the HLRCC tumors, is the presence of a characteristic large nucleus with a very prominent inclusion like orangiophilic or eosinophilic nucleolus, surrounded by a clear halo. Immunohistochemical studies did not provide a specific marker for these tumors, however, loss of heterozygosity at 1q32 and 1q42-44 was frequently found. These tumors are associated with poor prognosis and frequent spread to regional lymph nodes. At the moment, morphology is the best tool to recognize these tumors. Proper diagnosis of this syndrome by the pathologist may assist in early detection of these tumors.