Postirradiation pseudosclerodermatous panniculitis: three new cases with additional histopathologic features supporting the radiotherapy etiology.

Postirradiation pseudosclerodermatous panniculitis is a rare panniculitic disorder induced by radiotherapy. Clinically, it consists of an indurate plaque localized on the irradiated area that may appear months or even years after radiotherapy was administered. Histopathologically, postirradiation pseudosclerodermatous panniculitis is characterized by a mostly lobular panniculitis without vasculitis, with lipophagic granuloma involving the fat lobules, a variable inflammatory infiltrate of lymphocytes and plasma cells and sclerotic thickening of the connective tissue septa of the subcutis. We report 3 additional cases of this rare variant of panniculitis, in which besides the panniculitis findings, dermal vessels showed sclerotic vessel walls and atypical bizarre fibroblasts with large pleomorphic and hyperchromatic nuclei were interstitially arranged between collagen bundles of the dermis. These dermal findings represent additional histopathologic features supporting the pathogenic role of the radiotherapy in the development of this rare variant of panniculitis.