Anaplastic lymphoma kinase-positive large B-cell lymphoma with a diagnostic pitfall of carcinoma: a case report.

Anaplastic lymphoma kinase-positive large B-cell lymphoma (ALK+LBCL) is a rare non-Hodgkin lymphoma that exhibits a characteristic immunoblastic/plasmablastic morphology and is frequently expressing Clathrin-anaplastic lymphoma kinase fusion protein. Since being negative for T- and B- linage markers, this tumor is easy to be misdiagnosed, especially when it has unusual morphology and immunophenotype. Here, we report an ALK+LBCL with a diagnostic pitfall of carcinoma. The patient was a 28-year-old man with enlargement of a right submandibular lymph node. Morphologically, the lymph node had an unusual nodular growth pattern, with nodules surrounded by collagen bands. The neoplastic cells expressed epithelial membrane antigen, CD138, CD38, Mum-1, but negative for T- and B- linage markers, and showed a strong granular cytoplasmic Anaplastic Lymphoma Kinase staining pattern. Some tumor cells had the expressing of Cytokeratin.