Fine Needle Aspiration Of An Intranodal Follicular Dendritic Cell Sarcoma: A Case Report With Molecular Analysis And Review Of The Literature

Follicular dendritic cell sarcoma (FDCS) is a rare malignant neoplasm of follicular dendritic cell origin which can present a diagnostic challenge. Due to the rarity of this neoplasm, its molecular pathogenesis has not been fully elaborated. A previous series of 13 cases reported that 38% contained mutations of genes encoding proteins involved in negative regulation of NF-kappa B. NF-kappa B is a family of transcription factors regulated through multiple cellular processes known as the canonical and noncanonical pathways. Here we present the case of a 62-year-old man who presented with abdominal pain and systemic symptoms and was found to have a mass in the porta hepatis. Fine needle aspiration cytology demonstrated a spindle cell neoplasm with vesicular chromatin and prominent nucleoli with admixed lymphocytes. Surgical resection showed an intranodal, 7.3 x 5.5 x 3.5 cm, solid mass composed of plump, spindle to histiocytoid cells with ovoid nuclei and small, prominent nucleoli arranged in a whorled and fascicular pattern. The lesional cells stained positively for CD21, CD23, and CD35 by immunohistochemistry, consistent with a diagnosis of FDCS. Next-generation sequencing revealed pathologic mutations in three genes involved in NF-kappa B regulation pathways:NFKBIA,TNFAIP3, andTRAF3. A pathologicTP53mutation was also identified. This case report supports prior associations of the NF-kappa B pathway dysregulation and FDCS. Additionally, it is the first reported FDCS case withTRAF3mutation as well as the first reported case to suggest disruption in both the canonical and noncanonical NF-kappa B pathways in the same lesion.