Cutaneous deciduosis: a report of two cases of an unusual pseudomalignancy.

Cutaneous deciduosis represents a rare manifestation of cutaneous endometriosis in which typical endometrial glands and stroma are morphologically and physiologically transformed under hormonal influence. The transformed glands and stroma usually take on the microscopic appearance of uterine decidua but may mimic malignancy. We describe two cases of cutaneous deciduosis that presented in the post-partum period, but biopsies were not performed until a much later date. The first lesion arose on the perineum of a 31-year-old female after vaginal delivery, but a biopsy was not performed until 6 years after presentation. The second lesion grew in a cesarean section scar of a 26-year-old female with a history of ovarian adnexal endometriosis. Clinically described as a persistent post-operative hematoma, the lesion throbbed in synchrony with her menstrual cycles; a biopsy was also performed 6 years after presentation. Histopathologically, both specimens showed similar findings. Sections showed a multinodular proliferation of pale-staining epithelioid cells without significant nuclear atypia or conspicuous mitotic figures. Both showed focal glands that ranged from slit-like to slightly dilated and that contained a flattened epithelial lining without atypia. These unusual cases are presented to instruct about the pathologic findings of this entity in order to prevent the unnecessary diagnosis of malignancy.