Abstract
Post-irradiation morphea is a rarely reported side-effect of irradiation therapy, affecting about 1 of every 500 such patients. Differentiation from other processes affecting these patients, such as post-irradiation dermatitis, lymphedema, recurrent breast cancer, and angiosarcoma can be challenging. A multi-disciplinary approach is often required, usually involving skin biopsy. We describe two cases both presenting more than a year after radiation treatment with clinical findings of unilateral breast skin redness and thickening. Microscopic examination of the first patients biopsy revealed dermal fibrosis with a lymphohistiocytic infiltrate. CK7 and GATA-3 failed to reveal breast cancer and ERG did not reveal a vascular proliferation, but CD68 highlighted histiocytes within the dermis and there was loss of interstitial CD34 staining. The second patients biopsy, submitted with concern for recurrent breast cancer was initially interpreted as dermal fibrosis with rare foreign body giant cells. The specimen was reevaluated after the patient was seen in dermatology and clinical images were made available for review by a dermatopathologist. Subsequent evaluation revealed decreased interstitial space with loss of CD34 staining. CD163 highlighted interstitial histiocytes within a superficial and deep lymphoplasmacytic infiltrate. The histopathologic findings, with the clinical images, supported a diagnosis of post-irradiation morphea in both cases. Post-irradiation morphea should be included in the differential diagnosis for a mammary dermatitis presenting in those with a history of breast cancer treated with radiation. Although clinical presentation usually occurs within 1-3 years after irradiation therapy, delays of several decades have been reported. Helpful histopathologic findings include CD34 loss (as seen in morphea and other sclerodermoid processes) but with a histiocytic component that is not typical of traditional morphea.
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