Diffuse hyperplastic mesothelial cells in multiple lymph nodes: case report with review of the literature.

We report a case of diffuse hyperplastic mesothelial cells in multiple lymph nodes. Microscopically, the lymph nodes had a normal follicular pattern. The lymphatic sinus was extremely expanded, within the sinuses the epithelial-like cells proliferated actively in the form of sheets and clusters. Epithelioid-like cells had eosinophilic cytoplasm, prominent nucleoli and vesicular nuclei. Mitotic figures were rarely observed. These cells were immunopositive for Calretinin, CK5/6, D2-40, MC and Ckpan and immunonegative for S-100, HMB45, MelanA, TTF-1, CDX-2, Villin, ALK, CD30, CD20, CD3, CD1a and CD68. In addition, during a 22 months follow-up period failed to identify any malignant neoplasms, thus confirming the benign nature of these cells. It is the first reported case of diffuse hyperplastic of mesothelial cells mainly in the cervical lymph nodes associated with systemic multiple lymph node involvement. Awareness of this event is important for the pathologist in preventing the misdiagnosis of malignancy.