Heterotopic Epithelium in an Intramammary Lymph Node.

Heterotopic squamous-lined cysts and ductal epithelium occurring in an intramammary lymph node from a 23-year-old woman are described. The lesion presented as a 3 cm x 2 cm well-circumscribed mass lying anterior to the left anterior axillary line. Careful examination of the breast revealed no other clinically apparent lesions. The nodule was thought to represent a benign neoplasm and excisional biopsy was performed. Pathologic examination revealed a lymph node whose architecture was distorted by multiple squamous-lined cysts. The squamous epithelium demonstrated a prominent granular cell layer. No evidence of nuclear atypia was found within the squamous lining. Only rare cases of epithelial inclusions within axillary lymph nodes have been described. The majority have been unrelated to a breast malignancy and have followed a benign clinical course. Because these inclusions may lead to significant axillary or intramammary lymphadenopathy, they may be mistaken clinically for metastatic carcinoma. Disclosure of intranodal epithelial deposits on pathologic examination may result in an incorrect diagnosis of metastatic disease. However, careful evaluation of the epithelial nests will establish their benign character. Benign epithelial deposits within intramammary and axillary lymph nodes must be added to the list of heterotopic benign epithelial structures found in lymph nodes.