Extranodal follicular dendritic cell sarcoma intimately associated with the pancreas

Follicular dendritic cell sarcomas (FDCS) are rare tumors derived from non-migrating antigen-presenting cells. They are distinguished from other histiocytic and dendritic cells by their immunophenotype, which supports a mesenchymal, non-myeloid stem cell origin. A 63-year-old woman reported painless epigastric fullness for 20 years, and was eventually found to have a 16.0 cm mass indistinguishable from the pancreas and surrounding tissue. Initial needle biopsy showed a high-grade epithelioid malignant neoplasm. A Whipple resection was ultimately performed, and evaluation revealed a malignant epithelioid neoplasm with histologic and immunophenotypic features of FDCS. FDCS is a rare tumor that can involve virtually any nodal or extranodal site, and to our knowledge this is the first reported case of FDCS of the pancreas. This case report emphasizes that FDCS should be considered in the differential diagnosis of pancreatic neoplasms with focal cytokeratin positivity, so that appropriate IHC testing with FDC-associated markers can be used to confirm the diagnosis.