ALK+ anaplastic large cell lymphoma with cohesive, perivascular arrangements on cytology, mimicking a soft tissue sarcoma: a report of 2 cases.

An accurate recognition of a lymphoma at an extranodal site is essential to avoid unnecessary excisions. Fine needle aspiration cytology (FNAC) has been recognized as a useful tool in the primary diagnosis of soft tissue tumors. An anaplastic large cell lymphoma (ALCL), occurring in soft tissues, poses a diagnostic challenge. We present the cytomorphology of 2 cases of anaplastic lymphoma kinase (ALK)+ ALCL that displayed a perivascular arrangement, thereby mimicking a sarcoma. The patients were aged 16 and 9 years. While the former presented with multiple nodular soft tissue and bony lesions over the body, the latter complained of an axillary lump. FNAC smears in both cases showed pleomorphic cells, arranged in loosely cohesive groups around blood vessels and scattered singly, with prominent nucleoli and abundant, finely vacuolated cytoplasm. Interspersed were a few cells with embryoid nuclei. Differential diagnoses included a rhabdomyosarcoma and a lymphoma. On biopsy and immunohistochemistry, tumor cells were positive for vimentin, LCA, EMA, CD30 and ALK. ALCL should be considered in the differential diagnosis of pediatric soft tissue tumors, especially in cases with multifocal involvement. The presence of cohesive, perivascular arrangements on FNAC should not detract a cytologist for keeping this possibility in mind. Further, a careful search for the typical "hallmark" cells should be made.