Follicular dendritic cell sarcoma (FDCS) is recognized as a diagnostically challenging neoplasm requiring rigorous exclusion of more common entities and high index of suspicion for diagnosis. Here, we report an aggressive case of FDCS arising in the mediastinum, which due to sampling limitations and the inherent difficulty of diagnosis required extensive workup with multiple samples prior to definitive classification. The patient was a 35-year-old woman who presented with progressive dyspnea and mediastinal mass on imaging studies. The initial sampling of the lesion had histologic features raising consideration of FDCS, but was too limited to allow definitive diagnosis, while progressing rapidly enough to require administration of chemotherapy even prior to classification. Repeat samples obtained via fine-needle aspiration and bronchoscopy enabled the diagnosis of FDCS, and high-throughput sequencing revealed apparently pathogenic NF2 mutations previously not reported in this disease. Unfortunately, the patient died of widely metastatic disease, which we comprehensively documented at autopsy. Together, these observations provide previously unreported insights into the end stage of this disease and experience relevant to its prospective recognition and workup.
From the Departments of *Pathology and
†Molecular Diagnostics and
‡Division of Hematology and Oncology, VCU School of Medicine, Richmond, VA;
§Department of Pathology, Mayo Clinic, Rochester, MN;
∥Cancer Genomics Research, Foundation Medicine, Inc, Cambridge, MA; and
¶Department of Surgery, VCU School of Medicine, Richmond, VA.
Reprints: Steven Christopher Smith, MD, PhD, Departments of Pathology and Surgery, VCU School of Medicine, PO Box 980662, Richmond, VA 23298. E-mail: email@example.com.
A preliminary report of these findings was reported at the 2017 Annual Meeting of the US and Canadian Academy of Pathology, in San Antonio, TX.
D.C.P. is an employee of and has equity interest in Foundation Medicine, Inc. The other authors have no funding or conflicts to declare.