Cytomorphology of ALK+ Anaplastic Large Cell Lymphoma Displaying Spindle Cells Mimicking a Sarcomatous Tumor: Report of a Case

Anaplastic large cell lymphoma (ALCL) is a lymphoma of T-cell or null-cell lineage characterized by molecular abnormalities involving anaplastic lymphoma kinase (ALK) gene and expression of ALK protein and CD30. Cytologic diagnosis of this entity is often a challenge and diagnostic difficulties are encountered when cytomorphology deviates from the usual descriptions. The reports of FNAC diagnosis of ALCL are rather limited. Histology and immunohistochemistry are usually required to confirm the diagnosis. We discuss a case of ALCL suspected on cytology in which a differential diagnosis of soft tissue sarcoma was also considered because of the presence of spindle-shaped and strap cells. Histology and immunohistochemistry confirmed the diagnosis of ALK+ ALCL with tumor cells displaying strong immunoreactivity for leucocyte common antigen, CD3, ALK-1 and CD30. We emphasize that the cytological features which may help in distinguishing sarcomatoid ALCL from soft tissue sarcoma are the presence of hallmark cells, lymphoglandular bodies and admixed mature small lymphocytes. Diagn. Cytopathol. 2011; 39: 775-779. (C) 2010 Wiley-Liss, Inc.