Abstract
Paget disease of the breast is a malignant tumor that occurs primarily on the skin of the nipple, whereas extramammary Paget disease occurs on the skin in regions other than the breast, such as the pubis, perianal area, and axilla. Paget disease can also arise outside these areas; this is referred to as ectopic extramammary Paget disease. In this study, we present a case of a Japanese woman in her 70s who experienced simultaneous occurrence of two ectopic extramammary Paget disease lesions on the skin of the anterior chest and left buttock. Both lesions, exceeding 5 cm in diameter, were surgically excised, and the histopathological examination led to a diagnosis of ectopic extramammary Paget disease without invasion. To the best of our knowledge, this is the third reported case of multiple simultaneous ectopic extramammary Paget disease. Clinically, diagnosis of a patient with ectopic extramammary Paget disease is challenging because of its unusual location; however, the disease may be considered a differential diagnosis for Bowen disease.