Primary Cutaneous Lymphoma-Associated Pseudoepitheliomatous Hyperplasia Masquerading as Squamous Cell Carcinoma in a Young Adult.

Primary cutaneous anaplastic large cell lymphoma is a T-cell malignancy with atypical CD30 positive lymphocytes. Pseudoepitheliomatous hyperplasia is an uncommon finding in primary cutaneous anaplastic large cell lymphoma, and may mimic squamous cell carcinoma as pseudomalignancy. Careful attention of a pathologist to correct diagnosis of pseudoepitheliomatous hyperplasia and its underlying causes will help physicians to avoid inappropriate management. Here, we present a 22-year-old man referred to our hospital with a solitary nodule persistent on his forearm which was diagnosed as squamous cell carcinoma in the first biopsy. The lesion recurred after two months and histopathologic and immunohistochemistry examination revealed anaplastic large cell lymphoma with florid pseudoepitheliomatous hyperplasia which masquerading as well-differentiated squamous cell carcinoma. Diagnosis of pseudoepitheliomatous hyperplasia must guide the pathologist to search for underlying causes, such as primary cutaneous lymphoma. Pseudoepitheliomatous hyperplasia may mimic squamous cell carcinoma and this can result in inappropriate diagnosis and management.