Pseudosclerodermatous panniculitis after irradiation: an unusual complication of megavoltage treatment of breast carcinoma.

An unusual edematous and indurated erythema developed in four patients with breast carcinoma 1 to 6 months after conservative surgical treatment and irradiation. The radiation therapy consisted of megavoltage x-ray photon with or without either electron beam or iridium-192 interstitial boost. Several tissue biopsy specimens revealed pronounced lymphocytic dermal and fat inflammation in conjunction with focal areas of plasma cells. The connective tissue bundles were enlarged and hyalinized. Macrophages and isolated giant cells were noted in the dermis. One biopsy specimen showed elastic tissue in giant cell cytoplasm. No mucin, fibrin, formation of cysts, or calcification was present. Lipophages and hyaline connective tissue replaced some fat lobules. The radiation-induced changes of dilated and hyalinized blood vessels, endothelial cell hyperplasia, fibrosis associated with involution of epidermal appendages, and fibroblasts were present. This combination of radiation-related and inflammatory pathologic changes is unusual and emphasizes the remarkable qualities of this rare reaction. The clinical differential diagnoses of recurrent carcinoma, cellulitis, and connective tissue disease can be excluded by reviewing the pathologic characteristics.