Nodular spindle-cell vascular transformation of lymph nodes: a benign process occurring predominantly in retroperitoneal lymph nodes draining carcinomas that can simulate Kaposi's sarcoma or metastatic tumor

We describe a vasoproliferative nodular spindle-cell lesion representing a variant of vascular transformation of lymph-node sinuses and designated a nodular spindle-cell vascular transformation of lymph nodes. The lesion is most frequently identified in retroperitoneal lymph nodes excised in association with radical nephrectomies for renal cell carcinoma, but it can also be present in association with other malignant tumors. Occasionally it is seen in superficial lymph nodes in patients with no history of malignant neoplasms. This lesion can be confused with Kaposi's sarcoma or with a metastatic sarcomatoid carcinoma because of its spindle-cell composition, cellularity, occasional high mitotic activity, and frequent occurrence in the regional lymphatic drainage of a known malignancy.