Malignant Pleural Mesothelioma, Biphasic Type: An Unusual and Insidious Case of Rapidly Progressive Small Blue Cell Tumor

Malignant pleural mesothelioma (MPM) is a rare neoplasm. It predominantly affects elderly individuals aged over 70 years presenting with a unilateral pleural tumor usually associated with previous asbestos exposure. The respiratory symptoms are associated with ipsilateral pleural involvement with concomitant pleural effusions. The diagnosis of MPM is established by the morphologic and immunohistochemical features of a cytologic specimen. MPM can present as three histologic subtypes: epithelioid, sarcomatoid, or biphasic. We present a case of an 85-year-old Caucasian female with a history of occupational asbestos exposure. She complained of 1-week history of progressive sharp right flank and scapular pain with mild shortness of breath, dry cough and pleuritic chest pain. CT of the chest showed a large loculated right pleural effusion with adjacent pleural thickening. CT abdomen and pelvis was negative for other neoplastic findings. CT-guided core biopsy of the right pleural-based mass was positive for a spindle to plasmacytoid small blue cell tumor. An extensive immunohistochemical panel was non-specific. A focal OSCAR keratin and WT-1 expression in the absence of carcinoma markers, a malignant mesothelioma, biphasic type was diagnosed. Further workup with PET-CT and cytotoxic chemotherapy combined with immunotherapy or tyrosine kinase inhibitors was recommended by oncology. The patient refused further imaging and treatment, and palliative care was consulted.