Follicular dendritic cell sarcoma in the differential diagnosis of GATA3 positive tumors: A case report

We describe a novel pathology finding in a 40-year-old woman without a history of breast carcinoma who presented with axillary swelling. The patient underwent core needle biopsy followed by axillary dissection 6 months later. The core biopsy of the axillary mass was initially considered to be a carcinoma of unknown primary, and as the biopsy specimen showed a pleomorphic malignant neoplasm that was GATA3 positive, the working diagnosis became metastatic breast carcinoma. The patient underwent an axillary dissection and was referred to our center for continuation of care. In addition to being positive for GATA3, the neoplasm was positive for CD21, CD23 and CD35, and negative for keratins, EMA, mammaglobin GCDFP-15, CD138, S-100 protein and other markers. The diagnosis of follicular dendritic cell sarcoma was established. We believe it is important to be aware that follicular dendritic cell sarcoma can be positive for GATA3, to avoid misdiagnosis as a metastatic neoplasm and an exhaustive workup for a primary site.