Supplemental Material for: Primary Invasive Ductal Carcinoma of the Nipple Presenting as Isolated Axillary Lymphadenopathy: A Case Report

Fine-needle aspiration (FNA) cytology of the axillary lymph node was positive for malignancy, whereas cytology of the nipple lesion was negative. Because nipple-originating breast carcinoma with axillary lymph node metastasis was strongly suspected, the patient underwent total mastectomy with level II axillary dissection. Histopathological examination demonstrated IDC arising from the nipple ducts with Pagetoid spread to the nipple epidermis.

Ten metastatic axillary lymph nodes were identified. Immunohistochemistry of sample showed estrogen receptor negativity, progesterone receptor negativity, HER2 expression 3+, and a Ki-67 labeling index of 57.5%. The patient received adjuvant chemotherapy, anti-HER2 therapy, and post-mastectomy radiotherapy, and remained disease-free 18 months after surgery.</p><p dir="ltr">Conclusion:</p><p dir="ltr">This case highlights that nipple-originating IDC may present as axillary lymphadenopathy even when the nipple and breast appear normal on initial physical examination, MMG, and BUS.

When axillary nodal metastasis is detected without an identifiable breast lesion, carcinoma arising in the nipple-areolar complex should be included in the differential diagnosis. Breast MRI may be particularly useful for locating the primary lesion in this setting.</p>