As with other lymphomas, clinicians can only suspect lymphoma and only pathologists can confirm the diagnosis of lymphoma. The typical histological presentation of nasal extranodal NK/T-cell forest lymphoma is heterogeneous lymphocytes with angiocentric necrotic lesions. The immunophenotype of lymphoma cells is CD3ε+, CD56+, EBER+, and if CD56-, then EBER+ must also establish the diagnosis. In addition, tumor cells often express CD2, CD43, GrB, TIA-1, and perforin, without TCR gene rearrangement. Prognostic indicators include Ki-67 nuclear antigen expression rate, serum β2-MG and LDH levels, and peripheral blood EBV-DNA levels. The diagnosis of comorbidities and complications should consider lymphoma involving the central nervous system, nasal sinus infections, and phagocytic syndrome. Clinical staging of nasal extranodal NK/T-cell lymphoma: After pathological confirmation of breakage (and also before diagnosis) whole-body PET/CT, bone marrow examination, etc. are strongly recommended for disease staging. The disease can still be divided into stages I, II, III, and IV with reference to the Ann Arbor staging scheme, with stage I being the earliest and stage IV being the latest. Korean scholars also divide the disease into two stages: limited lesions (referring to lesions only in the upper gastrointestinal and respiratory tracts and without local spread) and extensive lesions (referring to lesions other than limited lesions). The diagnosis of lymphoma is divided into two steps: first, to determine whether it is lymphoma and which kind of lymphoma it is; second, to clarify how extensive the lymphoma is and to which stage it is clinically classified. This is crucial for choosing a treatment plan. If these two issues are not clearly investigated, it will be a muddle in terms of diagnosis, not to mention a good outcome.