Renal angiomyolipoma. DNA content and immunohistochemical study of classic and multicentric variants

Angiomyolipomas (AMLs) are polymorphic renal tumors that are composed of mature tissues and frequently associated with tuberous sclerosis; AMLs have long been considered hamartomatous in nature. We report the routine histologic and immunohistochemical features and DNA content analysis of two fatal cases of renal giant multicentric AML with distant organ involvement, and we contrast the findings with those of four similarly studied cases of classic solitary AML. Severe nuclear pleomorphism, significant mitotic activity, and necrosis, which are all characteristics of multicentric AML, were not seen in the cases of classic AML. Quantitation of DNA by image analysis of Feulgen-stained slides from paraffin-embedded blocks revealed an aneuploid pattern in the two cases of multicentric AML and an aneuploid pattern in one of the four cases of classic AML. Tumors in the liver, spleen, and lungs in one of the cases of multicentric AML were diploid. Immunohistochemical analysis revealed positive staining reaction of vascular and adipose tissue components with HMB-45 antibody in three of the six cases of AML. We conclude that AMLs may occur in a sarcomatous, infiltrating multicentric form involving multiple organs, that aneuploidy may be seen in lesions of both the multicentric AML and classic AML variants, that AMLs may feature DNA ploidy heterogeneity in multiple-organ sites, that HMB-45 immunoreactivity may be encountered in AMLs without evidence of nevomelanocytic differentiation, and that continued study of AMLs is needed to clarify further the histogenesis, lineage, clonality, and malignant potential of these tumors.