Sarcoid-like reaction in a HER2-positive breast cancer patient: A case report.

Introduction And Importance: Sarcoid-like reaction is a systemic granulomatous reaction that may develop in the lymph nodes and organs of cancer patients. Distinguishing a sarcoid-like reaction from metastasis is difficult. Accurate diagnosis of this reaction is key to preventing overtreatment.

Case Presentation: A 51-year-old woman presented with a lump in her left breast and swollen lymph nodes in her left axilla and infraclavicular fossa. A core biopsy was performed, leading to the diagnosis of grade 2 infiltrating ductal carcinoma, clinical stage T2N3M0 with estrogen and progesterone receptor negativity and human epidermal growth factor receptor-2 positivity. After neoadjuvant therapy, the tumor in her left breast reduced in size, but the lymph nodes remained swollen. Mastectomy and axillary lymph node dissections were performed. In the pathological findings, epithelioid cell granuloma was observed in the lymph nodes. Based on these findings, lymph node swelling was attributed to a sarcoid-like reaction.

Clinical Discussion: SLRs have been reported in 4-14% of cancer patients. Although there are various imaging modalities for detecting swollen lymph nodes, the differential diagnosis of cancer metastasis is often difficult.

Conclusion: Histological evaluation of swollen lymph nodes is required to prevent overtreatment; especially in cases where the tumor size is reduced by chemotherapy, but the lymph nodes remain swollen.