The natural killer (NK)/T-cell lymphoma is a rare, aggressive tumor affecting the mid facial area. It is associated with a dismal prognosis. We studied a case of advanced extranodal NK/T cell lymphoma, the nasal type, who presented to our institute and was misdiagnosed as rhinosinusitis. A 36-year-old man presented with complaints of nasal obstruction, fever, and swelling in the infraorbital region. Based on a high suspicion of allergic fungal sinusitis on imaging and biopsy, endoscopic debridement of the right maxillary sinus was done. Later histopathologic evaluation of granulation tissue from debrided material revealed NK/ T cell lymphoma. The patient deteriorated quickly. Soon after the chemotherapy, he went into tumor lysis syndrome (TLS) sepsis, and multiorgan failure. The natural killer (NK)/T-cell lymphoma is an uncommon, locally destructive tumor. Tumor lysis syndrome was managed with hemodialysis. However, cellulitis due to initial debridement of the maxillary sinus worsened due to neutropenia and probably lead to sepsis and death. Hence, clinicians and pathologists need to be vigilant about the presentation of this lymphoma, and a multidisciplinary approach would be helpful.