Background: Primary invasive ductal carcinoma of the vulva, also known as adenocarcinoma of mammary gland type (AMGT), is an exceedingly rare malignancy arising from specialized anogenital mammary-like glands (AGMLGs). Diagnosing this neoplasm requires rigorous differentiation from primary vulvar tumors and secondary metastasis from breast cancer. This study aims to report a rare case of primary vulvar ductal carcinoma and review its diagnostic, surgical, and therapeutic management based on contemporary evidence.
Methods: A 64-year-old female presented with an asymptomatic subcutaneous nodule in the left labium majus. Following the exclusion of a primary breast neoplasm via mammography and breast ultrasonography, the patient underwent volvectomy and bilateral inguinal lymphadenectomy. Detailed histopathologic evaluation, tumor staging, and comprehensive immunohistochemical (IHC) profiling—including hormone receptors, HER2 status, and breast-specific lineage markers—were performed.
Findings: Histopathological assessment revealed invasive ductal carcinoma (Grade 2) with clear surgical margins (10 mm) and positive lymph nodes (14/22), establishing a pathological stage IIIC (pT1c N1c M0). IHC demonstrated strong positivity for GATA3, CK7, ER (90% strong; Allred score 8/8), PR (80% strong; Allred score 7/8), and focal positivity for Mammaglobin and GCDFP-15. HER2 was negative (score 1+), while SOX10, p63, and CK20 were negative. Following multidisciplinary tumor board review, adjuvant radiotherapy and cytotoxic chemotherapy were deemed necessary.
Conclusion: The IHC profile showed complete phenotypic concordance with luminal breast carcinoma. Due to the scarcity of this disease and the lack of prospective randomized clinical trials, systemic therapies such as adjuvant endocrine therapy are extrapolated primarily from breast cancer management guidelines and case series. Clear surgical margins and nodal evaluation via SLNB remain pivotal for optimal oncologic control.