Background: In order for peritoneal metastases from a primary appendiceal mucinous neoplasm to occur, the wall of the appendix must perforate to allow mucus with tumor cells access to the peritoneal spaces. With progression the peritoneal metastases show a broad spectrum of tumor biology varying from indolent to aggressive activity.
Methods: The histopathology of peritoneal tumor masses was determined from the clinical material resected at the time of cytoreductive surgery (CRS). All groups of patients were treated by a uniform strategy that involved complete CRS and perioperative intraperitoneal chemotherapy. Overall survival was determined.
Results: From a database of 685 patients, four histologic subtypes were identified and long-term survival determined. Four hundred and fifty patients (66.0%) had low-grade appendiceal mucinous neoplasm (LAMN), 37 patients (5.4%) had mucinous appendiceal adenocarcinoma of intermediate subtype (MACA-Int), 159 patients (23.2%) had mucinous appendiceal adenocarcinoma (MACA), and 39 patients (5.4%) had a mucinous appendiceal adenocarcinoma with positive lymph nodes (MACA-LN). The mean survival of the four groups was 24.5, 14.8, 11.2 and 7.4 years, respectively (p < 0.0001). These four subtypes of mucinous appendiceal neoplasms were shown to have distinct survival estimates.
Conclusions: The estimated survival of these four histologic subtypes in patients having a complete CRS plus HIPEC is of value to the oncologist managing these patients. A mutations and perforations hypothesis was offered in an attempt to explain the broad spectrum of mucinous appendiceal neoplasms that exist. Inclusion of MACA-Int and MACA-LN as standalone subtypes was thought to be necessary.
Keywords: Cytoreductive surgery; Disseminated peritoneal adenomucinosis; Low-grade appendiceal mucinous neoplasm; Mucinous appendiceal adenocarcinoma; Mutation; Perforation; Peritoneal mucinous carcinoma; Tumor biology; Tumorigenesis.
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