Cutaneous Extranodal Natural Killer/T-Cell Lymphomas Histopathologically Mimicking Benign Inflammatory Disease.

Few studies have evaluated the histopathological features of cutaneous extranodal NK/T-cell lymphoma (ENKTL). The authors' study aims to describe cases of cutaneous ENKTL that histopathologically mimic benign inflammatory dermatosis. The authors searched the database of Asan Medical Center to identify cases of cutaneous ENKTL that were confirmed by skin biopsy between January 1998 and December 2014. The authors included cases that were initially diagnosed as benign inflammatory disorders on the histopathological examination, but finally diagnosed as cutaneous ENKTL on further evaluation. This study included 10 cases of cutaneous ENKTL. Six cases demonstrated nonspecific perivascular cellular infiltration, 2 cases demonstrated lupus erythematosus-like histological features, 1 case demonstrated psoriasiform lichenoid reaction, and 1 case demonstrated vasculitis-like features on histopathological examination. All cases were positive for CD56 and Epstein-Barr virus in situ hybridization. Perivascular infiltrations throughout the superficial and deep dermis with vasculopathy and panniculitic infiltration were common histopathological findings. The clinical features included 7 cases of erythematous to purpuric patches, 2 cases of facial swelling, and 1 case of cellulitis-like swelling. In conclusion, cutaneous ENKTL can histopathologically mimic benign inflammatory dermatosis. Cutaneous ENKTL should be suspected when histopathology shows perivascular dermal infiltration with vasculopathy and panniculitic cellular infiltration.