Extrafollicular reticulum cells in pathologic lymph nodes

Extrafollicular reticulum cells in lymph nodes are heterogeneous. They express cytokeratins, desmin, and/or vimentin as their intermediate filament profile. Using those markers, we undertook an immunohistochemical study of human lymph nodes under various pathologic conditions. Samples included 15 simple reactive lymph nodes, 7 follicular hyperplasia, 1 necrotizing lymphadenitis, 4 tuberculous lymphadenitis, 13 malignant lymphoma (9 non-Hodgkin's and 4 Hodgkin's lymphomas), and 11 metastatic adenocarcinoma. In lymph nodes with follicular hyperplasia, cytokeratin and/or desmin expressing reticulum cells displayed a characteristic dendritic meshwork in the subcapsular, perisinusoidal, and paracortical regions. In other forms reactive lymph nodes, they were similarly distributed but were less prominent. By SDS-PAGE and immunoblotting, cytokeratin polypeptides were identified. In necrotizing lymphadenitis, they were increased and the pattern of distribution was disturbed. In tuberculous lymphadenitis, they were also increased and located at nongranulomatous as well as in perigranulomatous areas. In lymphomas the reticular meshwork was entirely obliterated. Cytokeratin or desmin expressing reticulum cells were rarely seen within tumors. The reticular meshwork was also obliterated in metastatic carcinoma. However, the meshwork was maintained in uninvolved areas. In conclusion, extrafollicular reticulum cells displayed characteristic patterns of distribution under various pathologic conditions, and may be implicated in the pathogenesis of those pathologic conditions in human lymph nodes.

Histopathological and immunohistochemical studies of polymorphic reticulosis

This study reviewed 65 cases of polymorphic reticulosis (PR) with respect to clinical and histopathologic bases, and immunohistochemical studies were done using MT1 and UCHL as T-cell markers, MB2 as a B-cell marker and alpha-1-antichymotrypsin as a histiocytic marker. The results obtained were as follows: 1. The male to female ratio was 2.4:1 and the mean age of patients was 44.5 years. The sites involved primarily were the nasal cavity, tonsil and pharynx and about one-fourth of the total cases showed extensive involvement of two anatomical sites at initial presentation. 2. Almost all cases showed characteristic histologic features similar to those of peripheral T-cell lymphoma and showed positive reaction to the T-cell marker. The above immunohistochemical findings suggest strongly that quite a significant portion of PR is in fact T-cell lymphoma.