Primary malignant mesothelioma (MPM) is a rare malignancy that arises from the epithelial cells that line visceral cavities. The primary pleural presentation is known as the most commonly seen presentation and is best recognized clinically. Less commonly, mesothelioma can arise from epithelial cells lining other visceral cavities, including the peritoneum and pericardium. Primary peritoneal presentations are often difficult to diagnose due to vague symptoms such as abdominal distention, anorexia, and diffuse pain. These symptoms overlap with those of many more common gastrointestinal conditions, often leading to delayed diagnosis.
We report a male in his 40s with a past medical history of hypertension and diabetes mellitus type 2 who presented to the emergency room with non-specific abdominal complaints. He had a history of longstanding work on demolition sites. Treatment was initiated following studies that tested positive for H. pylori infection. A CT scan of the abdomen revealed nodular fat stranding of the omentum, with several confluent peritoneal nodules and small-volume ascites. An omental biopsy showed tumor cells positive for markers indicative of epithelioid-type malignant mesothelioma, with the peritoneum identified as the primary site.
A key piece of this patient’s case was long-standing exposure to demolition sites and asbestos. Asbestos exposure is a well-documented risk factor for the development of mesothelioma. This history was obtained but did not aid in guiding diagnostic practices due to overlapping symptomatology. The discovery of an H. pylori infection may have delayed the diagnosis of primary malignant peritoneal mesothelioma (PMPM) and its appropriate treatment, as H. pylori is a much more common condition.
We report a case of epithelioid primary malignant peritoneal mesothelioma (PMPM) in a Hispanic male with long-term occupational asbestos exposure, with the aim of emphasizing the diagnostic delay due to confounding H. pylori gastritis and Peritoneal Cancer Index (PCI) staging and prognosis. We emphasize that a detailed history, particularly occupational history, is a critical component of clinical assessment, alongside imaging and symptomatology.
Malignant mesothelioma (MPM) is an uncommon, aggressive tumor arising from mesothelial cells lining the pleura, peritoneum, pericardium, and tunica vaginalis. The pleural form accounts for most cases, while PMPM represents 8%-10% of cases in the United States, with an annual incidence of approximately 0.5-3 per million.
The pathogenesis is strongly linked to asbestos fiber exposure, with additional associations including simian virus 40 (SV40) contamination, germline breast cancer gene 1-associated-protein-1 (BAP1) mutations, prior abdominal radiation, and chronic peritoneal inflammation. The latency period between asbestos exposure and mesothelioma development often exceeds two decades. Compared with the pleural variant, PMPM frequently presents with non-specific symptoms. These include abdominal distension, discomfort, ascites, early satiety, and weight loss. The wide spectrum of symptoms mimics various gastrointestinal, hepatic, or gynecologic conditions. These factors may have led to diagnostic delays that worsened prognosis.
Histologically, the epithelioid subtype is most common in PMPM and confers a relatively favorable prognosis, with median survival approaching 51 months, versus biphasic (3 months) and sarcomatoid (6 months) variants. Treatment typically involves cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) when feasible, or systemic chemotherapy for unresectable disease. Staging PMPM is challenging due to its diffuse spread within the peritoneum. PCI is a validated tool for quantifying tumor burden across 13 abdominopelvic regions, with higher scores predicting worse outcomes and lower likelihood of complete cytoreduction.
Ethnicity is rarely discussed in PMPM literature. While Hispanic patients represent 13.5% of cases in U.S. registry data, outcome disparities remain poorly studied. [Footnotes omitted]
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