Diffuse Pleural Mesothelioma Initially Presenting as Cervical Lymphadenopathy: A Report of a Rare Case.

Diffuse mesothelioma is a rare malignant tumor arising from mesothelial cells, showing diffuse involvement of the pleura and having a strong association with asbestos exposure. Cervical lymphadenopathy as the initial presentation of pleural mesothelioma is very unusual to date. We report here such a rare case of diffuse pleural mesothelioma in a 42-year-old male patient who primarily presented with left-sided lower cervical lymphadenopathy. Fine-needle aspiration cytology (FNAC) from the lymph nodes demonstrated hypercellular smears with polygonal epithelioid cells arranged mostly as singly scattered cells, loosely cohesive clusters, monolayered pavement-like sheets, and spheroid groups. Many cells displayed binucleation, multilobed nuclei, cytoplasmic vacuoles, fuzzy cell borders, and mitotic figures. Guided tru-cut biopsy from the lymph node revealed diffuse sheets of atypical epithelioid cells with abundant eosinophilic cytoplasm, with large nuclei and prominent nucleoli in places. The tumor cells were immunopositive for pancytokeratin, CK5/6, EMA, Calretinin, D2-40, and WT1 while negative for all other relevant markers. Diffuse, irregular thickening and nodularity of left-sided pleura and mediastinal lymphadenopathy were identified on contrast-enhanced computed tomography (CECT). It is very important to consider metastatic pleural mesothelioma in the differential diagnosis of lymph node mass on FNAC, especially in the cervical region, to avoid misdiagnosis or delay in the correct diagnosis of this strikingly unusual presentation.