A case of peripheral T-cell lymphoma unspecified involving subcutaneous tissue.

A 36-year-old man presented with a 3-year-old red-brown plaque with subcutaneous nodules on his left thigh. Although a similar lesion was observed on his right thigh 3 years earlier, it spontaneously disappeared 1 year later. However, the lesion on the left thigh was growing larger. Histologically, the lesion showed a diffuse and dense infiltration of atypical lymphocytes extending from the superficial dermis to the subcutaneous tissue. Severe lobular panniculitis, composed of small- and medium-sized atypical lymphocytes and large normal histiocytes, was observed in the subcutaneous adipose tissue. Immunohistochemical studies revealed a post-thymic T-cell phenotype. A genetic analysis demonstrated a rearrangement of the T-cell receptor chain gene. The left skin lesion also gradually disappeared after skin biopsy without therapy, and he continues to be in remission.