Ossified diagnosis: sarcoidosis masquerading as metastatic breast cancer.

A 40-year-old woman was referred to the Breast Unit with a solid lump in her right breast. Investigations revealed an invasive lobular carcinoma. The patient underwent a right-sided mastectomy and sentinel lymph node (LN) biopsy, which confirmed axillary LN involvement. The postsurgery staging CT showed unusual enlargement of mediastinal and hilar LN bilaterally. This was consistent with positron emission tomography/CT and MRI, which further established the presence of several bone lesions. Determining the pathology within the LN and bones was pivotal in providing an accurate diagnosis and deciding subsequent management. However, histopathological analysis of the initial endobronchial ultrasound-guided fine-needle aspiration biopsy of mediastinal LN failed to identify definitive metastatic breast cancer cells. The case was extensively discussed in several multidisciplinary team meetings. Collective evidence, including clinical presentation, comparative imaging analysis, and further biopsies confirmed sarcoidosis with bone involvement-mimicking metastatic disease.