Pyrexia of Unknown Origin Caused by Non-Hodgkin's Lymphoma: A Diagnostic Challenge for Clinicians.

Non-Hodgkin's lymphomas (NHLs) are a group of lymphoproliferative diseases that originate from different cell types, namely B cells, T cells, or natural killer cells. Herein, we report the case of a 69-year-old male patient who presented with a gradual-onset, intermittent, low-grade fever for four months and a right-sided neck lump for two months. On examination, a right-sided enlarged lymph node sized 1 × 1 cm2 was noted, which was mobile, hard in consistency, and non-tender. No other lymphadenopathy was noted in other parts of the body. Imaging and biochemical studies done at the initial stages did not reveal features in favor of any lymphoproliferative disorders, and the two lymph node biopsies done two weeks apart were inconclusive as well. An extended panel of investigations was done in view of excluding other infective and inflammatory pathologies, which was negative, making the patient undiagnosed of any disease state despite being symptomatic for four months. Finally, the third lymph node biopsy tested positive, which paved the way for the diagnosis of NHL. This diagnosis underlines the importance of this case. Following the diagnosis, the patient was initiated on a few chemotherapeutic agents, after which a mild symptomatic improvement was achieved.