Breast cancer with sarcoidosis that mimicked metastatic disease

What happened, in summary

A 40-year-old woman found an irregular lump in the upper right breast during self-examination. Imaging and biopsy identified a large grade 2 invasive lobular carcinoma that was ER-positive, PR-positive, and HER2-negative. She chose a right mastectomy with sentinel lymph-node biopsy. Pathology showed a 90 mm tumor and macrometastatic cancer in 2 of 4 sentinel nodes, including extracapsular extension. Postoperative imaging then raised concern for widespread metastatic disease because enlarged hilar and mediastinal nodes and multiple skeletal lesions were metabolically active. The pattern was unusual, and an initial endobronchial ultrasound-guided node sample did not confirm breast-cancer spread. Additional multidisciplinary review and repeat biopsies showed sarcoidosis with bone involvement rather than distant metastases. With disseminated breast cancer ruled out, treatment focused on the known locoregional disease. She received external-beam radiation to the chest wall and axilla and continued letrozole and goserelin. Hydroxychloroquine was later tried for sarcoidosis, which was managed separately from the breast cancer. At follow-up, she attended the Breast Unit every six months, and her most recent mammogram showed no recurrent breast cancer. Tissue confirmation prevented benign inflammatory lesions from being treated as metastatic cancer.