SHM Converge Scientific Abstract ePoster Gallery-Ovarian Imposter: Diagnosis of a Rare Malignant Peritoneal Mesothelioma in a Female Patient

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This case describes a 59-year-old woman who presented with abdominal distention, weight gain, and shortness of breath. Her history included hypertension, alcohol use disorder, type 2 diabetes, and possible childhood asbestos exposure. Exam showed marked ascites, and CT imaging revealed hepatomegaly, large-volume intraperitoneal fluid, and diffuse abdominal/peritoneal abnormalities. Her CA-125 was elevated at 226 U/mL, and diagnostic paracentesis showed a low SAAG with many reactive mesothelial cells. Pelvic MRI demonstrated bilateral ovarian lesions, initially raising concern for primary ovarian cancer. Cytology was first interpreted as metastatic Müllerian high-grade adenocarcinoma.<br /><br />She underwent extensive cytoreductive surgery including total hysterectomy, bilateral salpingo-oophorectomy, portal lymph node excision, and omentectomy. Final pathology, however, confirmed diffuse malignant peritoneal mesothelioma of epithelioid subtype involving multiple abdominal and pelvic structures. This rare cancer has an incidence of about 1 per million people annually and is associated with asbestos exposure, genetic factors, radiation, and chronic inflammation. Because it can mimic ovarian or other intra-abdominal malignancies, diagnosis is often difficult and delayed.<br /><br />Two main treatment approaches were discussed: cytoreductive surgery with HIPEC, or systemic therapy with immunotherapy and surgery. The patient was started on carboplatin, pemetrexed, and pembrolizumab in May 2025, with surveillance imaging. She responded well but developed recurrent cytopenias, leading to discontinuation of carboplatin. She continues to require occasional paracentesis for symptomatic ascites but is currently asymptomatic with stable imaging.<br /><br />The report emphasizes that malignant peritoneal mesothelioma is rare, aggressive, and often presents nonspecifically, making early diagnosis challenging. Although treatment options have improved, the disease remains incurable and carries a high mortality rate.

Asset Subtitle

Amelia Oldham

Meta Tag

Author List Amelia Oldham, Ashley Matias, Ashna Manhas, Sean Oenick

Category Clinical Vignettes

Concept Malignant Peritoneal Mesothelioma

Concept Surgical Pathology

Concept Immunophenotyping

Concept Diffuse Epithelioid Malignant Mesothelioma

Concept Cytoreductive Surgery

Distinguished Non-Finalist

Presenter Organization Uniformed Services University of Health Sciences

Presenting Author Amelia Oldham

Track Adult

Keywords

malignant peritoneal mesothelioma

epithelioid subtype

ascites

ovarian cancer mimic

CA-125 elevation

asbestos exposure

cytoreductive surgery

HIPEC

carboplatin pemetrexed pembrolizumab

peritoneal malignancy

Malignant Peritoneal Mesothelioma

Surgical Pathology

Immunophenotyping

Diffuse Epithelioid Malignant Mesothelioma

Cytoreductive Surgery