title: Follicular dendritic cell tumor of the mediastinum.
abstract: Follicular dendritic cell tumor (FDT) is a rare neoplasm usually occurring in the laterocervical lymph nodes, but presentations elsewhere are also well documented. We report a case of FDT in a 48-year-old man with myasthenia gravis, in whom a slow-growing mediastinal mass that had been surgically excised manifested after 3 years with a local recurrence in the same site. The lesion was aspirated and cytology showed a tumor composed of groups of oval or elongated cells intermingled with several mature small lymphocytes. On histology, the tumor was highly cellular with abundant perivascular lymphocytic infiltration; large cells with pale, eosinophilic cytoplasm and round nuclei, arranged in fascicles often showed a storiform pattern. Occasional binucleated cells were also present. A panel of antibodies showed positivity only for CD21 and CD35, and a weak response to S-100. Electron microscopy showed that the layer cells had convoluted nuclei and elongated interdigitating processes with desmosome-like junctions. The definitive diagnosis of FDT can be concluded only with positive immunostaining for CD21 and CD35. However, in the presence of a mixed population of lymphocytes and larger eosinophilic cells the hypothesis of FDT should always be considered.
authors.affiliation: Section of Pathology and Cytopathology, Department of Oncological and Surgical Sciences, Faculty of Medicine, University of Padova, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Fassina
authors.forename: F
authors.initials: F
authors.lastname: Marino
authors.forename: A
authors.initials: A
authors.lastname: Poletti
authors.forename: F
authors.initials: F
authors.lastname: Rea
authors.forename: N
authors.initials: N
authors.lastname: Pennelli
authors.forename: V
authors.initials: V
authors.lastname: Ninfo
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D002467:Cell Nucleus / Q000648:ultrastructure; D003713:Dendritic Cells / Q000737:chemistry / Q000473:pathology*; D015622:Epithelioid Cells / Q000648:ultrastructure; D006801:Humans; D007124:Immunoenzyme Techniques; D008224:Lymphoma, Follicular / Q000737:chemistry / Q000473:pathology* / Q000601:surgery; D008297:Male; D008479:Mediastinal Neoplasms / Q000737:chemistry / Q000473:pathology* / Q000601:surgery; D008854:Microscopy, Electron; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000150:complications / Q000473:pathology; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D015388:Organelles / Q000648:ultrastructure; D017463:Receptors, Complement 3b / Q000032:analysis; D017464:Receptors, Complement 3d / Q000032:analysis; D009418:S100 Proteins / Q000032:analysis
chemical_list: D014408:Biomarkers, Tumor; D017463:Receptors, Complement 3b; D017464:Receptors, Complement 3d; D009418:S100 Proteins