ALK-negative anaplastic large cell lymphoma mimicking a soft tissue sarcoma.

Anaplastic lymphoma kinase protein (ALK)-negative anaplastic large cell lymphoma (ALCL) has a vast morphologic spectrum and may mimic many other types of malignancies both cytologically and histologically. There are only a few published case reports/series describing the cytomorphologic features of ALCL on fine-needle aspiration (FNA) biopsy specimens. We describe a case of ALK-negative ALCL mimicking a high-grade soft tissue sarcoma of the thigh in a 62-year-old man. The characteristic morphologic findings on FNA and core biopsy along with the immunophenotypic profile are described and reviewed. The diagnosis of ALCL on FNA biopsy may be difficult, but can be done successfully with the use of ancillary tests. Therefore, it must be considered in the differential diagnosis of lesions with pleomorphism, anaplasia, and wreath-like or horseshoe-shaped nuclei to ensure that adequate material is obtained for ancillary studies.