Extranodal NK/T-cell lymphoma, nasal type (ENKL), is an uncommon subtype of EBV associated lymphoma usually characterized by aggressive clinical course. We report an atypical sinonasal ENKL case with long-lasting indolent behaviour, developed in the setting of a polymorphic EBVassociated lymphoproliferative disorder (LPD). A 52-year-old woman had suffered from chronic sinusitis and nasal obstruction since 2000, moderately worsened during the last years (marked enlargement of the sino-nasal

more »

... a at MRI in 2011) with elevated anti-VCA IgG and IgM titers. Three subsequent biopsies revealed slightly increasing morphophenotypic atypia, ranging from a polymorphic B-and T-cell EBV positive proliferation (diagnosed in 2011, but not fulfilling CAEBV diagnostic criteria) to an overt monomorphic mildly atypical T LPD without necrosis and angiocentricty diagnosed as ENKL in 2013 upon immunophenotype and TCR-γ gene clonal rearrangement. Clinically indolent ENKL with low-grade morphology is extremely rare and diagnostically challenging; while the few reports in the literature describe long-survival in ENKL treated patients comparing histologically neoplastic lesions at onset and recurrences, no reports are published on the slow progression from a polymorphic EBV-related T/NK proliferation to a histologically overt clinically indolent ENKL in an untreated patient who only received occasional steroid administration. Keywords ENKL, Indolent, CAEBV, EBV V. Tabanelli et al. 597