Cytokeratin positive anaplastic large cell lymphoma: Difficulty in differentiation from metastatic carcinoma

Cytokeratin and epithelial membrane antigen (EMA) are usually included in the first panel of immunomarkers used to differentiate metastatic carcinoma from lymphoma in cases presenting with enlarged lymph nodes. While carcinomas are cytokeratin and EMA positive, most lymphomas are negative for the above. However, recently few cases of cytokeratin positive lymphomas have also been reported. Here, we describe a very rare case of cytokeratin positive anaplastic large cell lymphoma (ALCL) masquerading as a poorly differentiated carcinoma. Simultaneously, we also discuss the differential diagnosis and difficulty in differentiation from metastatic carcinoma in such a scenario. Review of literature shows that this is probably the first case report of anaplastic lymphoma kinase negative-ALCL seen in a young adult.