Encapsulated papillary carcinoma arising in ectopic breast tissue in the vulva: A case report and review of literature.

[BACKGROUND] Encapsulated papillary carcinoma (EPC) is a rare breast neoplasm, typically seen in postmenopausal women, and is exceedingly uncommon in ectopic breast tissue. We report one such case of EPC arising in ectopic breast tissue of the vulva, highlighting diagnostic and management challenges.

[CASE PRESENTATION] A 51-year-old female patient presented with a slowly enlarging, painful cystic vulvar mass. Clinical examination revealed a firm, mobile nodule on the right labia majora. Imaging studies were inconclusive, and differential diagnoses included Bartholin gland cyst, epidermal inclusion cyst, and vulvar carcinoma. Histopathological evaluation following excisional biopsy revealed features consistent with encapsulated papillary carcinoma arising in an ectopic breast tissue with close margins. Multidisciplinary evaluation prompted re-excision, which showed no residual carcinoma. Sentinel node sampling was not performed.

[CONCLUSION] EPC in vulvar ectopic breast tissue is a diagnostic rarity, often not considered in the differential diagnosis of vulvar masses. The absence of myoepithelial cells and the presence of a fibrous capsule are key histological features distinguishing EPC from other papillary neoplasms. Management mirrors that of native breast EPC, emphasizing complete surgical excision and hormone receptor profiling to guide adjuvant therapy. Given the indolent nature of non-invasive EPC, prognosis is generally favorable. This case underscores the importance of considering ectopic breast tissue in the differential diagnosis of vulvar masses and maintaining a low threshold for using breast-specific and hormonal immunohistochemistry for timely and accurate diagnosis.