Abstract

The presence of benign mesothelial cell inclusions in the mediastinal lymph node is extremely rare and thus difficult for the pathologist distinguishing from sinus histiocytosis, metastatic carcinoma, or metastatic mesothelioma. We recently had a case of benign mesothelial cell inclusions in the mediastinal lymph node, which is initially misinterpreted as metastatic carcinoma of unknown origin. However, further clinical studies failed to identify the primary site. Subsequent immunostaining with calretinin demonstrated the strong nuclear and cytoplasmic immunore-activity, suggesting that these cells are mesothelial cells. It is important that when the nodal changes resemble metastatic carcinoma morphologically in the mediastinal lymph nodes, but the primary site can not be identified clinically, the possibility of mesothelial cell inclusions should be raised and the proper use of immunohistochemistry in conjunction with a clinical finding is recommended.

• Keywords: Inclusion;Mediastinum;Mesothelium