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

Abstract

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.

Keywords: asbestos; malignant pleural mesothelioma.

Figure 1. Posteroanterior and portable chest X-ray

(Left figure) Posteroanterior chest X-ray showing dense peripheral right lung pleural-based opacity with blunting of the right costophrenic angle. Interstitial prominence of the right lung is present with right lower lung opacity. Nodular opacities are seen in the left midlung. (Right figure) Portable chest X-ray 2 months prior to the image at the left, showing no focal airspace opacity. A calcified nodule is seen at the right cardiophrenic junction which is unchanged compared to previous images.

Figure 2. CT of the chest without contrast

(Left figure) Large loculated right pleural effusion within the right lung base with adjacent pleural thickening anteriorly, multiple small medium and large size nodular masses scattered throughout both lung fields, especially involving the right lung and right pleura. (Right figure) Large area of nodular consolidation and mass is seen along the right lateral chest wall midportion measuring up to 5.5 x 3 cm in length and thickness. Multiple left lung nodules vary in size from 1 cm up to 2 cm in size.

Figure 3. Histological examination and immunohistochemical stains

Histological examination (A) Hematoxylin and eosin low power and high power view insert at the right upper corner showing sheets of small blue cells with focal necrosis, high nuclear to cytoplasmic ratio, and focal areas of spindle cell formation. Immunohistochemical stains showing (B) CK CAM5.2 focally positive (C) WT1 focally positive and (D) Vimentin diffusely positive.