Epidermal inclusion cyst in an axillary lymph node with breast cancer: A case report.

Epidermal inclusion cyst (EIC) is a benign lesion rarely discovered within lymph nodes. The present case report introduces an EIC incidentally discovered during an axillary lymph node biopsy in a patient with invasive ductal carcinoma of the breast. A 55-year-old woman presented with a breast mass. Ultrasound revealed a suspicious mass, and a core needle biopsy confirmed the diagnosis of invasive ductal carcinoma. Lumpectomy and sentinel lymph node biopsies were performed. Histopathological examination revealed tumor-free lymph nodes, with one of them harboring a keratinous EIC. EICs typically arise from entrapped epidermal cells. Their presence in lymph nodes is exceptionally rare. While the origin of such inclusions remains unclear, various theories exist, including anomalous embryonic development, implantation, and metaplasia. This report highlights the unique presentation of an EIC within an axillary lymph node. Recognizing this entity is crucial to avoid misdiagnosis of malignancy and unnecessary interventions.