Introduction

Pseudomyxoma peritonei (PMP) is a rare malignant condition characterized by dissemination of mucin-producing neoplastic cells throughout the peritoneal cavity, resulting in progressive accumulation of gelatinous ascites [1,2]. The disease most commonly originates from a perforated appendiceal mucinous neoplasm, although ovarian, colorectal, pancreatic, and other gastrointestinal primary sites have been reported [1].

Management of PMP has evolved substantially over the past several decades. Cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) has become the standard treatment approach for appropriately selected patients and has significantly improved long-term outcomes compared with historical debulking procedures [3].

PMP was originally described as a distinct clinicopathologic syndrome associated with progressive intraperitoneal accumulation of mucinous tumor deposits [4]. The estimated incidence is approximately two to four cases per million individuals annually, making PMP an uncommon but clinically significant entity [5]. Patients frequently present with vague and nonspecific symptoms, including abdominal distension, bloating, abdominal pain, early satiety, and weight loss [6]. Although abdominal symptoms predominate, unusual clinical presentations have been reported, including presentation as a scrotal mass, inguinal hernia, uterine prolapse, and findings initially attributed to gynecologic pathology [7-10]. Because the clinical manifestations of PMP overlap with numerous benign and malignant gastrointestinal disorders, diagnosis is often delayed until imaging studies or surgical exploration reveal characteristic mucinous ascites.

The pathogenesis of PMP remains incompletely understood. Current evidence suggests that disease behavior is primarily determined by the underlying mucinous neoplasm and its histopathologic characteristics. Microbial influences have also been investigated as potential modifiers of the tumor microenvironment. Although Helicobacter pylori is a well-established cause of gastric malignancies [11], no causal relationship with PMP has been established. Studies have identified distinct microbial populations within PMP that may influence tumor biology through mechanisms such as modulation of β-catenin signaling pathways [12,13].

Histologically, PMP encompasses a spectrum ranging from low-grade mucinous carcinoma peritonei, which generally follows a more indolent clinical course, to high-grade disease and signet-ring variants associated with increased recurrence rates and reduced survival [14-16]. Immunohistochemical markers including CDX2 and SATB2 are frequently used to support an appendiceal or colorectal origin and assist in diagnostic classification [17]. Thoracic involvement is uncommon but has been reported in advanced disease and may complicate management and prognosis [18].

Computed tomography (CT) remains the preferred imaging modality for evaluating disease extent and identifying features such as peritoneal implants, scalloping of visceral surfaces, and omental caking [19]. Disease recurrence remains common, and outcomes are strongly influenced by histologic grade, disease burden, and completeness of cytoreduction [5,15,16].

Given the rarity and heterogeneity of PMP, individual case reports continue to provide valuable insight into atypical clinical presentations, diagnostic challenges, and treatment limitations. We present a case of high-grade PMP notable for atypical endocrine and genitourinary symptoms that preceded recognition of the underlying malignancy, initially nondiagnostic MRI, repeated nondiagnostic cytologic studies despite an established diagnosis, radiographic findings concerning for thoracic involvement, and rapid clinical deterioration that ultimately precluded CRS-HIPEC.