Psoas/iliacus muscle invasion from mucinous appendiceal neoplasm. Radiologic appearance and outcome of treatment in 3 patients.

BACKGROUND: Mucinous appendiceal neoplasms have a pattern of metastases that is different from the other gastrointestinal cancers. The first site for cancer dissemination is the peritoneal space surrounding the primary tumor and this is followed by increasingly extensive peritoneal spread. Invasion of the psoas and iliacus muscle is an unusual phenomenon.

METHOD: From a prospective database of appendiceal mucinous neoplasms treated by cytoreductive surgery (CRS) and perioperative hyperthermic chemotherapy (HIPEC), patients with psoas muscle invasion were reviewed. Their clinical features and treatments were tabulated.

RESULTS: Three patients with ages 33, 60, and 63 were identified. Two patients had disease progression into the psoas muscle 33 and 95 months after CRS plus HIPEC. One had dissecting mucinous tumor into psoas, iliacus and quadratus lumborum muscle at the time of diagnosis of the appendiceal mucinous neoplasm. All three survived at least five years from their initial treatment.

CONCLUSION: Despite the fact that mucinous tumor invasion was outside the peritoneal cavity, long term benefit from psoas muscle resection with a mucinous appendiceal neoplasm is possible and resection possibly with HIPEC should be considered.