Diffuse Malignant Peritoneal Mesothelioma Presenting with Psammomatous Calcification on a Cervical Smear

Background: Psammoma bodies in cervical smears are rare but may be associated with benign and malignant diseases of the female genital tract. Case: A 52-year-old nulliparous woman presented with a 2-month history of intermittent vaginal spotting and post-coital bleeding. A cervical smear showed an inconclusive high-grade glandular lesion with psammomatous calcification. Previous cervical smears had been normal. This smear contained papillary tissue fragments, occasional spheres of gland-like cells and frequent psammoma bodies. The patient underwent a laparoscopic hysterectomy, bilateral salpingo-oophorectomy and omentectomy. The surface of the omentum and both ovaries contained psammoma bodies with groups of cells identical to those in the cervical smear. Within the omentum, there were invasive malignant epithelioid cells positive for CK7, CK5/6, calretinin, D2-40, WT-1, CK5/6, p16 and EMA. Desmin and PAX-8 immunostains were negative. There was also evidence of BRCA1-associated protein 1 (BAP1) dysfunction compatible with diffuse malignant peritoneal mesothelioma (DMPM). Conclusion: We describe the first reported case of DMPM presenting with an abnormal cervical smear, a rare but important differential diagnosis to consider in abnormal cervical smears showing psammomatous calcification.