Adenocarcinoma of the Appendix Presenting as a Palpable Right Thigh Mass

Intra-abdominal and intra-pelvic pathologies initially presenting in extra-abdominal/pelvic locations is unusual. This spread predominantly occurs with infectious processes to sites including the buttock, thigh, and calf. The routes of extension into adjacent anatomically weak compartments include the pelvic outlet, greater sciatic foramen, obturator foramen, inguinal or femoral canal, weak bones, or along nerves and blood vessels. Malignant neoplasms of the appendix, while extremely rare and accounting for only 0.4% of all gastrointestinal cancers, is one of the intra-abdominal pathologies that can spread via these routes. Adenocarcinoma of the appendix accounts for 10-20% of primary appendiceal tumors. They usually present as acute appendicitis or as a right lower quadrant abdominal mass when associated with a mucocele. We report the unique case of mucinous appendiceal adenocarcinoma in a 57-year-old male who initially presented with a right thigh mass secondary to extension of the neoplasm from the right lower quadrant through the femoral canal. A similar presentation of a mucinous appendiceal cystadenoma has been previously reported, however, to our knowledge, this is the first case of a malignant appendiceal tumor extending into the thigh. We review the literature and discuss imaging findings and treatment of this tumor.