NK/T-cell Lymphoma, Cutaneous
In cutaneous NK/T-cell lymphomas, the tumor cells show diffuse infiltration of dermis and often subcutaneous tissues. There is perivascular and periadnexal growth pattern with ulceration and necrosis. The lymphoma cells infiltrate in between the adipocytes creating a pattern mimicking subcutaneous panniculitis-like T-cell lymphoma. Extranasal sites are less commonly involved and include skin, gastrointestinal tract, testis, lung, eye, and soft tissues. These are the same sites to which nasal NK/T-cell lymphoma disseminates. The mechanism is homophilic binding of CD56+ lymphoma cells to CD56/N-CAM molecules richly expressed in these sites. Patients with extranasal lesions often present at late stages with involvement of multiple anatomic sites.