Late-Stage Erythema Elevatum Diutinum Mimicking a Fibroblastic Tumor: A Potential Pitfall.

Erythema elevatum diutinum (EED) is a rare dermatosis with evolving histopathological features that vary according to the age of the lesions, with a variable fibrosis and a fascicled proliferation of spindle cells in late phases. The authors present an otherwise healthy 57-year-old woman with multiple indurated nodules on the inner aspect of both feet. Skin biopsy showed storiform interlacing bundles of spindled cells with plump nuclei and some areas with neutrophils and leukocytoclasia. CD34 and S100 were negative. This case is noteworthy clinically due to its location and its histopathological presentation that comprises a wide differential diagnosis, including inflammatory pseudotumor, dermatofibrosarcoma protuberans, superficial nodular fasciitis, hyalinized leiomyoma, sclerosing spindle cell perineuroma, and sclerotic fibroma. The authors have reviewed the main histopathological and immunohistochemical features that help in the differential diagnosis of this rare variant of EED. A careful search for leukocytoclasia and neutrophilic vasculitis is mandatory to establish the right diagnosis of nodular or late-stage EED and avoid the pitfall of considering this a neoplastic process.