FASCIN, A SENSITIVE NEW MARKER FOR REED-STERNBERG CELLS OF HODGKINS-DISEASE - EVIDENCE FOR A DENDRITIC OR B-CELL DERIVATION

Immunohistochemical localization of human fascin, a distinct 55-kd act in-bundling protein, was determined for a wide variety of lymphoid tis sues (364 specimens total). In non-neoplastic tissues, reactivity was highly selective and localized predominantly in dendritic cells. In th e thymus, this protein was distinctly localized to medullary dendritic cells. In reactive nodes, interdigitating reticulum cells of T zones, cells in subcapsular areas, and cells of the reticular network were r eactive, with variable reactivity observed for follicular dendritic ce lls. Splenic dendritic cells of the white pulp and sinus-lining cells of the red pulp were reactive. Endothelial cells of all tissues exhibi ted variable reactivity. Lymphoid cells, mlyeloid cells, and plasma ce lls were uniformly nonreactive. In the peripheral blood, only dendriti c (veiled) cells were reactive for fascin. A striking finding was obse rved for cases of Hodgkin's disease (total 187 cases). In all cases of nodular sclerosis (132), mixed cellularity (34), lymphocyte depletion (2), and unclassified types (5), all or nearly all Reed-Sternberg cel ls and variants were immunoreactive for fascin. Neoplastic cells exhib ited strong diffuse cytoplasmic staining and frequently assumed dendri tic shapes, particularly in the nodular sclerosis type, producing an i nterdigitating meshwork or syncytial network of cells. In cases of mix ed cellularity type, neoplastic cells generally appeared more discrete . In all 14 cases of nodular lymphocyte predominance type, L&H variant s were nonreactive. By contrast, neoplastic lymphoid cells of only 24 of 156 (15%) other lymphoid neoplasms (127 B cell, 27 T cell, and two null cell evaluated) were reactive for fascin. Fascin represents a hig hly effective marker for detection of certain dendritic cells in norma l and neoplastic tissues, is an extremely consistent marker for Reed-S ternberg cells and variants of Hodgkin's disease (except LCH types), a nd may be helpful to distinguish between Hodgkin's disease and non-Hod gkin's lymphoma in difficult cases. The staining profile for fascin mi ses the Possibility of a dendritic cell derivation, particularly ly an interdigitating reticulum cell, for the neoplastic cells of Hodgkin's disease, notably in nodular sclerosis type. However, as fascin expres sion may be induced by Epstein-Barr virus infection of B cells, the po ssibility that viral induction of fascin in lymphoid or other cell typ es must also be considered in Epstein-Barr virus-positive cases.