Sinister Masquerade: A Rare Case of Primary Bone Follicular Lymphoma Mimicking Chronic Osteomyelitis and Tuberculosis

Abstract

Background:
Primary bone lymphoma (PBL) is a rare extra-nodal manifestation of non-Hodgkin lymphoma (NHL), constituting less than 1% of all NHLs and approximately 7% of malignant bone tumors. While diffuse large B-cell lymphoma is the predominant subtype, follicular lymphoma (FL) rarely presents as isolated primary bone disease. Accurate histopathological evaluation is therefore pivotal for diagnosis and management.
Case Report:
We describe a 26-year-old immunocompetent male presenting with progressive pain and swelling over the left humerus. Imaging revealed a destructive lytic lesion with soft tissue extension, initially suggestive of chronic osteomyelitis. Empiric antibiotic and anti-tubercular therapies were initiated without improvement. The patient subsequently developed pathological fracture, chest wall
extension, lymphadenopathy, systemic “B” symptoms, and a cavitary lung lesion. Laboratory evaluation revealed anemia, elevated inflammatory markers, and markedly raised β2-microglobulin. Definitive diagnosis was achieved by excisional lymph node biopsy and bone marrow examination, which demonstrated Grade 3A follicular lymphoma with positive immunohistochemistry for CD20, CD10, BCL-2, BCL-6, and C-Myc, and a high Ki-67 index. The patient deteriorated rapidly and succumbed before initiation of definitive oncologic therapy.
Conclusion:
Primary bone follicular lymphoma represents a rare and diagnostically challenging entity that may masquerade as chronic osteomyelitis or skeletal tuberculosis. This case highlights the need for early consideration of lymphoproliferative disorders in atypical, treatment-refractory bone lesions.