OCCULT PRIMARY BREAST CARCINOMA PRESENTING AS ISOLATED CERVICAL LYMPHADENOPATHY: A COMPREHENSIVE MULTIMODAL MANAGEMENT APPROACH

Background: Occult primary breast carcinoma (OPBC) is an uncommon clinical entity characterized by metastatic lymph node involvement in the absence of an identifiable primary lesion within the breast on clinical examination or imaging. In most patients, OPBC presents with axillary lymph node metastasis. Presentation as isolated cervical lymphadenopathy is extremely rare and may lead to diagnostic difficulty because it can resemble malignancies arising from other primary sites. This case report describes a rare presentation of occult breast carcinoma manifesting as isolated cervical lymphadenopathy in a postmenopausal woman. Case Presentation: A 70-year-old postmenopausal woman presented with a painless swelling in the left posterior cervical region that had progressively enlarged over six weeks. Clinical breast examination, bilateral mammography, and contrast-enhanced breast magnetic resonance imaging did not reveal any primary breast lesion. Fine-needle aspiration cytology demonstrated metastatic adenocarcinoma. Ultrasound-guided core biopsy followed by immunohistochemical analysis showed strong estrogen receptor and progesterone receptor expression, GCDFP-15 positivity, CK7 positivity, and negative staining for TTF-1 and CK20, confirming a breast origin of the metastasis. The disease was staged as cT0 N3c M0 according to the AJCC 8th edition and classified as hormone receptor-positive, HER2-negative (Luminal A-like subtype).The patient underwent selective cervical lymph node excision followed by adjuvant anthracycline-taxane chemotherapy.