A 59-year-old Caucasian woman presented with non-specific abdominal discomfort. Clinical examination revealed a palpable abdominal mass. There was no other abdominal symptoms of significance or unintentional weight loss nor constitutional symptoms. She had no significant past medical history and was not on any regular medications. She was a current smoker with a 30-pack year history. She had no known occupational or environmental exposure to asbestos.
Computed tomography (CT) of the abdomen demonstrated extensive peritoneal omental caking with infiltration to the anterior abdominal wall (Fig. 1). Ultrasound-guided biopsy of the abdominal mass revealed large, pleomorphic epithelioid cells, within fibrous stroma. These cells stained positively with AE1/3, CK7, CK5/6, WT1, calretinin and D2 40. The cells were negative for BerEP4, PAX8, CA125, ER, CD34, ERG, P63, P40, Melan A, Gata3 and mammaglobin. The morphology and immunohistochemical profile supported a diagnosis of epithelioid malignant mesothelioma. (figure -2a).
The patient subsequently presented with exertional dyspnoea. A CT scan of chest revealed moderate right sided pleural effusion, bilateral hilar and mediastinal lymphadenopathy, extensive bilateral pulmonary parenchymal & interstitial opacity along with interlobular septal thickening, suggestive of lymphangitic spread. (Fig. 3). A bone scan and a Brain CT were negative for distant metastases. Pleural fluid examination showed it was an exudative effusion, cytological examination was inconclusive. Bacterial cultures and acid fast bacilli were negative.
In order to obtain a definitive diagnosis of the pulmonary infiltrates, she underwent a bronchoscopy with trans-bronchial lung biopsy (TBLB). Bronchial washing and lavage did not reveal malignant cells and was negative for microbial or fungal elements. The TBLB confirmed pulmonary epithelioid malignant mesothelioma, demonstrating lung tissue with infiltrating cells, similar to that of initial peritoneal biopsy, also stained positively with CK7, calretinin, WT1 and D2 40. They were negative for Napsin A, TTF1 and P40 confirming pulmonary metastatic malignant epithelioid mesothelioma (Fig. 2b). The TBLB biopsy samples were small and did not contain muscle/fat tissue, hence no invasion into muscle/fat were demonstrated. Lymphovascular invasion was not seen either. Although TBL biopsy did not did not demonstrate lymphangitic invasion, however, the CT scan findings were highly suggestive of lymphangitic spread. Unfortunately the patient had an aggressive course of disease and died within three months of initial presentation, prior to the initiation of any systemic treatment.