Metachronous vulvar ectopic breast cancer, a case report and literature review.

•When two or more primary tumors arise at the same time, they are considered synchronous.•A metachronous tumor in a new primary that develops after an initial cancer diagnosis.•The diagnosis of vulvar breast cancer is primarily histopathologic, based on morphology and immunostaining.•Identifying a cancer as a metastasis versus as synchronous/metachronous significantly impacts staging and treatment.