Is erythema nodosum coexisting with lesions of the breast a suggestive sign for idiopathic granulomatous mastitis?

Coexistence of idiopathic granulomatous mastitis and erythema nodosum is very unusual. In this paper, we present a patient with idiopathic granulomatous mastitis accompanied by erythema nodosum to highlight the diagnostic importance of erythema nodosum and its relationship with treatment response of breast lesion. A 39-year-old female with a breast lesion and erythema nodosum was started on treatment with corticosteroids before the results of her histopathological evaluation were obtained. The response to treatment was very quick. Erythema nodosum totally disappeared and the breast lesion regressed noticeably within a week. We think that erythema nodosum associated with a breast lesion may be a sign suggestive of idiopathic granulomatous mastitis and can be used for the evaluation of the response to corticosteroid treatment. More case reports are needed to justify the use of erythema nodosum as a sign suggestive of idiopathic granulomatous mastitis.