Radiation therapy for cutaneous blastic plasmacytoid dendritic cell neoplasm: a case report and review of the literature.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare tumor that usually arises in the skin. Most patients develop skin lesions, which may be isolated and subsequently spread to affect the whole body. The prognosis is poor. Although BPDCN is usually treated by chemotherapy, radiation therapy is used in some cases (e.g., isolated lesions, elderly patients, or patients with comorbidities). The overall therapeutic efficacy and dose of radiation therapy remain unknown. We herein present a case of successful radiation treatment for BPDCN in a 77-year-old Japanese patient and describe the results of the first literature review on BPDCN of the skin initially treated with radiation therapy. The patient developed a raised, tender, pruritic skin lesion on his left forearm and similar multiple disseminated lesions on his right shoulder and precordial region. Histological and immunohistochemical examination of biopsy specimens of the skin lesions on the left forearm and right shoulder established a diagnosis of BPDCN. The other multiple skin lesions were considered to be disseminated BPDCN. The patient declined chemotherapy and instead elected radiation therapy for the lesion on his left forearm (total of 30 Gy). The skin lesion regressed until only pigmentation was present on the forearm, but the untreated lesions rapidly expanded. Although BPDCN of the skin may respond favorably to initial radiation therapy, it tends to recur in the short term. The optimal dose of radiation therapy remains unclear. Our findings provide a baseline for future research.