Clonal identity and histologic difference in peripheral T-cell lymphoma with follicular helper T-cell phenotype simultaneously occurring at common bile duct and lymph nodes.

We present the first case of peripheral T-cell lymphoma, not otherwise specified expressing follicular helper T-cell markers with different histologic features simultaneously involving the common bile duct and pericholedochal lymph nodes in a 72-year-old woman patient. Abdominal computed tomography revealed a localized wall thickening in the common bile duct. With the impression of cholangiocarcinoma, pancreaticoduodenectomy was done. Microscopically, dense small lymphoid cells with only minimal cytologic atypia were observed with occasional lymphoepithelial-like lesions, whereas many atypical large cells infiltrated the pericholedochal lymph nodes. Immunohistochemically, most small cells in the bile duct and the large atypical cells in the lymph nodes were all reactive for follicular helper T-cell markers including CD4, PD-1, and CXCL-13. BIOMED-2 based polymerase chain reaction using the DNA template from either the bile duct lesion or the lymph node revealed identical but different dominant clonal peaks, indicating these 2 lesions represent a spectrum of the same disease.