Beyond Occam’s Razor: Diffuse Large B-Cell Lymphoma With Concurrent Acid-Fast Bacilli Positivity–A Case Report

In tuberculosis-endemic regions, necrotizing lymphadenitis with Acid-Fast Bacilli (AFB) is often presumed to indicate tuberculous etiology, but this assumption may lead to misdiagnosis when immunophenotypic evaluation is not performed. In this report, we present the case of an immunocompetent elderly man who presented with prolonged high-grade fever, progressive abdominal distension, and stable cervical and submandibular lymphadenopathy. He had been empirically started on antitubercular therapy (ATT) following fine-needle aspiration cytology findings of granulomatous lymphadenitis with AFB positivity, but failed to improve. On re-evaluation, he was found to have hepatosplenomegaly and generalized lymphadenopathy, and he fulfilled criteria for hemophagocytic lymphohistiocytosis (HLH). Imaging suggested a lymphoproliferative disorder, and repeat lymph node biopsy with immunohistochemistry confirmed Diffuse Large B-Cell Lymphoma (DLBCL). Despite therapy for both, prognosis was suboptimal. This case highlights the role of timely tissue diagnosis and immunohistochemistry in preventing delays in appropriate treatment and argues against the Ockham’s Razor principle.