Pathogenesis of histologic variations of appendiceal mucinous neoplasms

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.

Rare occurrence of pseudomyxoma peritonei (PMP) syndrome arising from a malignant transformed ovarian primary mature cystic teratoma treated by cytoreductive surgery and HIPEC: a case report

Background

Pseudomyxoma peritonei (PMP) syndrome is a disease process that typically occurs from ruptured appendiceal mucocele neoplasms. PMP syndrome arising from malignant transformation of an ovarian primary mature cystic teratoma (MCT) is a pathogenesis rarely encountered.

Case Presentation

Herein, we report a 28-year-old patient evaluated and treated for a right ovarian mass and large volume symptomatic abdominopelvic mucinous ascites. Molecular profiling and genetic analysis revealed mutations in ATM, GNAS, and KRAS proteins while IHC demonstrated gastrointestinal-specific staining for CK20, CDX2, CK7, and SATB2. Peritoneal cytology showed paucicellular mucin. Diffuse peritoneal adenomucinosis (DPAM) variant of PMP arising from a ruptured ovarian primary MCT after malignant transformation to a low-grade appendiceal-like mucinous neoplasm was ultimately confirmed. Treatment included staged therapeutic tumor debulking and right salpingo-oophorectomy followed by cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC).

Conclusions

Our report builds upon the existing literature supporting this aggressive treatment option reserved for advanced abdominal malignancies utilized in this patient with a rare clinical entity.

GNAS is frequently mutated in both low-grade and high-grade disseminated appendiceal mucinous neoplasms but does not affect survival. Hum Pathol. 2014;45:1737-1743. [PMID: 24925222 DOI: 10.1016/j.humpath.2014.04.018]

We analyzed a series of 55 disseminated appendiceal mucinous neoplasms treated at our institution for GNAS and KRAS mutations in an attempt to correlate mutation status with clinicopathological findings and patient survival. GNAS mutations (p.R201H, c.602G>A and p.R201C, and c.602C>T) were identified in 17 (31%) of 55 of disseminated mucinous neoplasms and were found in 8 (35%) of 23 low-grade mucinous neoplasms, 7 (37%) of 19 high-grade mucinous adenocarcinomas lacking a signet ring cell component, and 2 (15%) of 13 high-grade mucinous adenocarcinomas with a signet ring cell component. All 7 mucinous adenocarcinomas composed of pure (>95%) signet ring cells harbored wild-type GNAS. There was no significant association between GNAS mutations and sex and age (both with P > .05) or between GNAS mutations and individual adverse histologic features including cytologic grade, destructive invasion, tumor cellularity, angiolymphatic invasion, perineural invasion, and signet ring cells (all with P > .05). KRAS mutations were identified in 22 (40%) of 55 disseminated mucinous neoplasms. GNAS-mutated disseminated appendiceal mucinous neoplasms more frequently harbored concurrent KRAS mutations compared with GNAS wild-type tumors (65% versus 29%, P = .018). GNAS mutations were not significantly associated with overall survival (both with P > .05). Only overall tumor grade was an independent predictor of overall survival in the multivariate analysis (P = .01). Our results indicate that GNAS mutations are frequently identified in both low-grade and high-grade disseminated appendiceal mucinous neoplasms indicating that GNAS mutation status cannot be used to distinguish between low-grade from high-grade appendiceal mucinous neoplasms.