Nasal Extranodal Natural Killer/T-cell Lymphoma Imitating Squamous Cell Carcinoma: A Case Report

Nasal extranodal NK/T-cell lymphoma (NNKTL) is a lethal disease due to poor prognosis with rapid progress. A 56-year-old man complained of left nasal obstruction and blood-stained nasal drip for two months. Incisional biopsies were performed at the outpatient department three times, and the diagnosis of SCC was made. The patient underwent wide excision of the entire lesion via endoscopic sinus surgery with navigation. Final pathologic report revealed NNKTL. Pathological examination of the tumor revealed overlying epithelium presenting as pseudoepitheliomatous hyperplasia (PEH), which mimicked SCC invasion, with infiltration of atypical lymphocytes in the deeper sections. Immunohistochemistry supported the diagnosis of NNKTL. Chemoradiotherapy was administered, and a complete response was achieved at the two-year follow-up. The correct diagnosis of NNKTL is essential for prompt treatment and prevention of superfluous surgery. Although the link between PEH and NNKTL may lead to a misdiagnosis of SCC, multiple large and deep biopsies can prevent this dilemma. A biopsy showing ulceration or necrosis can indicate PEH and imply potential malignancy. Repeated biopsies and complete immunohistochemical studies are important for diagnosing NNKTL.