[Two benign vascular tumors of the kidney capsule]

Capsular tumors of the kidney are uncommon or poorly documented. The authors report two cases of benign vascular tumors: a so-called "vascular leiomyoblastoma" and a glomus tumor. An ultrastructural study of the first tumor demonstrated smooth muscular characteristics. Obvious histological features of glomus were seen in the second. Immunohistochemical study revealed positive immunoreactivity for epithelial and mesenchymal antibodies in the two tumors. Glomus tumor originates from the particular system of vessels in the capsule. Histogenesis of the vascular leiomyoblastoma is more controversial. This tumor could be akin to leiomyomas of the renal capsule and intra parenchymatous leiomyomas; lymphatic origin and even a glomangiomatous nature are also possible explanations.