Cutaneous hypertrophic lupus erythematosus: a challenging histopathologic diagnosis in the absence of clinical information.

Hypertrophic lupus erythematosus (HLE) is rare variant of chronic cutaneous lupus characterized histologically by irregular epidermal hyperplasia associated with features of classic chronic cutaneous lupus, including interface changes. Lesions frequently demonstrate reactive squamous atypia of the basal layer and may show histopathologic overlap with other more common cutaneous atypical squamoproliferative lesions. Typical histologic features of cutaneous lupus, such as follicular plugging, angiocentric lymphocytic inflammation, and dermal mucin, are very helpful clues to the diagnosis of hypertrophic lupus erythematosus. Recently, immunohistochemistry for CD123 used to detect increased plasmacytoid dendrocytes in hypertrophic lupus erythematosus has proven to be diagnostically useful. A high index of suspicion for hypertrophic lupus erythematosus is essential to avoid overdiagnosis of squamous neoplasia, particularly in limited cutaneous biopsies in the absence of adequate clinical information.