Collecting duct meningeal carcinomatosis.

Collecting duct carcinoma (CDC) is an aggressive primary renal neoplasm that represents a distinct subtype of renal cell carcinoma. Histochemical (eg, mucicarmine) and immunohistochemical (eg, Ulex europaeus) studies, taken in concert with the gross and histologic findings, allow differentiation of CDC from the conventional varieties of renal cell carcinoma in most cases. Collecting duct carcinoma generally pursues a more aggressive course than conventional renal cell carcinoma. Metastases to regional lymph nodes, bone, adrenal glands, lung, and skin have been reported in CDC. We describe the case of a 26-year-old man who presented with a clinical and radiologic impression of multifocal meningioma. Biopsies of the meninges and extracranial soft tissues revealed metastatic adenocarcinoma; subsequent studies suggested metastatic CDC. Ultrasound-guided biopsy was performed on a subsequently identified renal mass, which showed features consistent with CDC. To our knowledge, this is the first reported case of meningeal carcinomatosis due to CDC. The diagnostic features of this tumor are discussed.