Comparative histopathologic analysis of cutaneous extranodal natural killer/T-cell lymphomas according to their clinical morphology.

Background: Few studies have evaluated the histopathologic features of cutaneous extranodal natural killer (NK)/T-cell lymphoma (ENKTL), and the histopathologic spectrum of this disease according to its clinical morphology remains unclear.

Objective: This study investigated the differences in pathologic findings of cutaneous ENKTL depending on clinical morphology.

Methods: A total of 41 cases of cutaneous ENKTL were included. Skin lesions were classified according to clinical morphology as: (i) nodular lesions, (ii) cellulitis or abscess-like swellings and (iii) erythematous to purpuric patches. Histopathologic variables were compared between groups.

Results: Perivascular infiltration of tumor cells and vasculopathy in the dermis and subcutaneous layer were common microscopic findings irrespective of clinical morphology. Erythematous to purpuric patches were mainly composed of small-sized tumor cells, whereas medium- to large-tumor cells were predominant in lesions of other clinical morphologies. The density of tumor cell infiltration was significantly higher in cellulitis or abscess-like lesions or nodular lesions compared with erythematous to purpuric patches. A panniculitis-like pattern and angiocentricity were less common in patch lesions than in cellulitis-like swelling and nodular lesions.

Conclusion: There is a histopathologic spectrum of cutaneous ENKTL that is dependent on the clinical morphology.