In this study, we report a very rare case of mucinous cystadenocarcinoma with huge metastatic lesion on the thigh. A 73-year-old man was admitted to our hospital complaining of a huge mass on his right thigh. Magnetic resonance imaging showed a cystic lesion. We performed open biopsy of the tumor twice, but could not detect any viable neoplastic cells. We then performed en bloc resection of the tumor. Myxomatous tumor extended invasively in the intramusclar region. The results of post-operative histological examination indicated mucinous adenocarcinoma. Because this patient had underwent excision of the appendical tumor in 1993, we investigated the specimens of both the appendix and thigh. Pathological report revealed metastatic mucinous cystadenocarcinoma consistent with the previously resected primary appendix cancer.
To our knowledge, no case of mucinous cystadenocarcinoma with skeletal muscle metastasis has ever been reported.