Radiation port erythema multiforme: erythema multiforme localized to the radiation port in a patient with non-small cell lung cancer.

A 75-year-old man was treated with stereotactic radiation to 50 gray units in 4 fractions for stage IB non-small cell lung cancer. Radiotherapy was directed at the right lower lobe segment of the lung and lasted 4 days. He developed radiodermatitis, which completely resolved within a few weeks after radiotherapy was finished. Three months after completing radiation therapy, he developed a pruritic red lesion within his radiation port on his right mid back with the formation of blisters a week later. Two weeks after the onset of the patient's blisters, cutaneous examination showed individual and convergent erythematous papules and plaques with superficial scaling at sites of resolving vesicles located within the radiated area (Figures 1 and 2). The patient had neither symptoms of mycoplasma pneumoniae, nor lesions or history of present or past herpetic infection. Also, he had not recently been placed on any new medications, and he did not have any other erythema multiforme-associated risk factors. A biopsy from the erythematous lesions showed a band-like infiltrate of lymphocytes in the dermis. The overlying epidermis contained necrotic keratinocytes and there was alteration of the basal layer. Correlation of the clinical presentation and pathologic changes established a diagnosis of erythema multiforme localized to the radiation port. The patient was treated with topical triamcinolone acetonide 0.1% cream twice daily for 10 days and once daily for 4 days. His lesions resolved and there was mild hyperpigmentation of the affected area.