Subcutaneous Sparganosis of the Breast.

A 77-year-old African American woman presented to the dermatologist with two pruritic lumps in her right breast. She reported traveling to Mexico on a cruise ship two years prior to the onset of her lesions, but denied a history of previous breast masses or malignancy. Despite former radiographic evaluation by her internist revealing benign growths, and despite dermatologic treatment with intralesional steroid injections, a third new, firm nodule developed in her right breast. One such nodule eventually formed into an ulcer, and a punch biopsy revealed thin-walled vascular channels in loose inflamed stroma, coarse fibrosis, calcareous corpuscles, and an elongated parasite. Further review confirmed the parasite to be Sparganum, which is the larval stage of cestodes in the genus Spirometra. Sparganosis is a rare parasitic infection caused by the plerocercoid larva of the diphyllobothroid tapeworm. Though subcutaneous sparganosis of the breast is exceedingly rare, clinicians should consider this infection in their differential of nodular breast masses.