Peripheral T-Cell lymphoma (PTCL) accounts for 12–26% of all non-Hodgkin lymphomas, but approximately 30% of these neoplasms cannot be further classified and are, therefore, diagnosed as not otherwise specified (NOS). PTCL NOS derives from mature CD4+ or CD8+ αβ TCR T lymphocytes, but its etiology remains unknown, despite the presence of EBV in some cases. Patients are usually adults, with a predominance of males and the lymph nodes are the most affected locations. The skin and the gastrointestinal tract are the two most affected extranodal locations. In the oral cavity this heterogeneous and aggressive neoplasm represents the most common T-cell lymphoma, except in Asia and Central/South America where extranodal NK/T-cell lymphoma predominates. It more often presents as destructive painful ulcerative swellings, with variable necrotic regions. The palate and the gingiva are the most affected locations. Oral PTCL NOS may have bone involvement and destruction. This neoplasm is characterized by a diffuse proliferation of polymorphic cells, ranging from small to medium to large atypical cells, necrosis is common and angiocentricity occurs in many cases. The prognosis of patients is usually very poor, with 5 years overall survival rates ranging from 20% to 30% in most series.