Anaplastic large cell lymphoma: A great mimic on cytology

Anaplastic large cell lymphoma (ALCL) is a T-cell lymphoma, accounting for <5% of non-Hodgkin's lymphoma. Cutaneous involvement can be primary or secondary arising in systemic ALCL. The diagnostic feature in both is the presence of pleomorphic, CD30 positive hallmark cells. We present a case of ALCL in a 19-year-old male presenting as an ulcerated scalp swelling. Clinical impression was actinomycosis or scrofuloderma. Cytology smears showed large dispersed pleomorphic cells with hyperlobated nuclei and multinucleated giant cells. The differentials considered were ALCL, rhabdomyosarcoma, and poorly differentiated carcinoma. Immunocytochemistry (ICC) showed positivity for leukocyte common antigen (LCA) and CD30 while negativity for desmin, favoring ALCL. Computed tomography (CT) showed a lytic paravertebral lesion. Subsequently, both paraspinal and scalp lesions were biopsied and immunochemistry confirmed the diagnosis of ALCL. Thus, cutaneous involvement in ALCL can resemble inflammatory and other neoplastic lesions clinically and cytologically. Hence, a high index of suspicion and ICC can aid in the correct diagnosis on fine needle aspiration cytology (FNAC).