Solitary erythematous nodule on the breast

In this clinicopathological case, we describe the case of a female in her sixties with relapsed IgG kappa plasma cell myeloma, commonly known as multiple myeloma (MM), on no active therapy who presented to dermatology with a solitary erythematous nodule on her right breast, biopsied as cutaneous involvement by MM. We include clinical, dermoscopic, and histopathologic images of the patient’s striking lesion. We then provide a brief review of the literature on cutaneous infiltration by MM along with discussion of the differential of plasma cell neoplasms of the skin, which can appear similar on H&E, but are differentiated by immunohistochemical staining.