Malignant peritoneal mesothelioma-a diagnostic challenge.

Malignant peritoneal mesothelioma is a rare cancer originating primarily from the peritoneum with a poor prognosis and non-specific clinical presentation. We present a case of a 60-year-old male, retired metallurgy engineer who initially presented with shortness of breath, lethargy, weight loss, vague abdominal pain and night sweats. Extensive workup for almost 2 months finally leads to the diagnosis of primary malignant peritoneal mesothelioma based on immunohistochemical analysis of loss of BAP1 gene. The patient was deemed non-suitable for surgical management and started on palliative carboplatin and pemetrexed. In conclusion, histological diagnosis is essential for peritoneal diseases before considering it as a metastasis from other primary tumours. Furthermore, immunohistochemical analysis and genetic profiling may also guide towards the diagnosis and possible treatment.