Conclusions

PMP is a rare malignancy that may present with atypical symptoms and initially inconclusive imaging findings, contributing to delayed diagnosis. This case highlights the limitations of cytology and minimally invasive tissue sampling in mucinous peritoneal disease. Although the diagnosis was initially established by exploratory laparotomy at an outside institution, repeated minimally invasive procedures after transfer failed to provide confirmatory tissue until diagnostic laparoscopy demonstrated extensive unresectable disease and high-grade mucinous adenocarcinoma with signet-ring cells. Adequate tissue sampling may therefore be required to confirm the diagnosis, establish histologic grade, perform immunohistochemical characterization, and guide treatment planning.

The patient's unusually aggressive clinical course, characterized by severe cachexia, ventilator-dependent respiratory failure, declining functional status, and radiographic findings concerning for thoracic involvement, ultimately precluded treatment with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) and limited systemic therapy to a single cycle of palliative FOLFOXIRI. Early recognition and timely referral to specialized peritoneal surface malignancy centers are essential, as progression to advanced disease and deterioration in functional status may preclude potentially curative treatment. This case underscores the importance of maintaining a high index of suspicion for PMP in patients with unexplained progressive ascites or persistent atypical abdominal symptoms and highlights the value of multidisciplinary evaluation in optimizing diagnostic accuracy and treatment planning.