Metastatic Mucinous Adenocarcinoma and Carcinoid Tumor Arising From a Mature Cystic Teratoma of a Horseshoe Kidney.

Concurrent primary carcinoid tumor and primary mucinous adenocarcinoma arising within a mature cystic teratoma of a horseshoe kidney is a rare event and has been reported once in the literature. We present the first case where this tumor subtype has metastasized to lymph nodes. Treatment included open partial nephrectomy, lymph node dissection, and adjuvant chemotherapy with temozolomide and capecitabine. Due to the rare combination of tumor histologies, it is unlikely that this cohort will ever be able to be adequately studied to determine a standard of care. Thus extrapolation of treatment methods of similar tumors will continue to guide treatment.