A Rare Case of Non-Hodgkin Lymphoma With Ankle Involvement: Diagnostic and Therapeutic Challenges.

Non-Hodgkin lymphoma (NHL) is a diverse group of malignancies primarily originating in the lymphatic system. Musculoskeletal involvement, especially in joints such as the ankle, is exceedingly rare. Accurate diagnosis is often complicated by overlapping features with other conditions like osteomyelitis or malignancies. This case report aims to highlight the diagnostic and therapeutic challenges associated with joint-related NHL presentations. A 49-year-old man presented with a three-month history of left ankle pain. Initial imaging, including contrast-enhanced magnetic resonance imaging (MRI), suggested osteomyelitis. To exclude malignancy, a whole-body positron emission tomography (PET) scan was performed, which indicated a high suspicion for malignancy. An open biopsy was conducted, and samples were analyzed for pathology and microbiology. The pathological evaluation revealed high-grade B-cell NHL. Preoperative laboratory findings were unremarkable, but further hematological workup confirmed the diagnosis. The patient was referred to oncology and commenced on a combination of chemotherapy and radiotherapy. At the six-month follow-up, the patient reported significant pain relief, and follow-up PET-computed tomography (CT) imaging showed no evidence of recurrence or metastasis. Although rare, NHL should be considered in the differential diagnosis of joint and bone lesions. This case highlights the importance of a multidisciplinary approach, including radiological, pathological, and oncological evaluations, in ensuring accurate diagnosis and effective treatment planning. Early intervention and targeted therapy significantly improved the patient's outcome.