ALK-negative Anaplastic Large Cell Lymphoma Presenting as Back Pain.

Anaplastic lymphoma kinase (ALK)-negative anaplastic large cell lymphoma (ALCL) is a distinct subtype of mature T-cell non-Hodgkin lymphoma characterized by large, strongly positive CD30 lymphoid cells that lack expression and rearrangement of the ALK gene. Here, we present a unique case of ALK-negative ALCL in a 34-year-old male patient who presented with acute on chronic back pain. Initial emergent MRI spine demonstrated lytic changes of L3 and L4 with probable psoas fluid collection, with high suspicion for Pott's disease. However, subsequent work-up including a CT-guided bone biopsy revealed ALK-negative ALCL. Patient underwent radiation to his lumbar spine and psoas muscle, with good radiographic response in those areas, however, further imaging with PET/CT showed widespread metastatic disease. Considering the burden of his disease, the patient received chemotherapy with BV-CHP, and achieved good response to therapy notable on his repeat PET/CT after his third cycle. Unfortunately, due to insurance coverage, patient transitioned his care to a different facility and no further information could be obtained. This case highlights an infrequent and unique presentation of ALK-negative ALCL, where progressive lumbar back pain in a young individual without B symptoms or lymphadenopathy warranted additional diagnostic workup for malignancy without anchoring to common diagnoses.