Paracortical nodular T-cell lymphoma: Identification of an unusual variant of peripheral T-cell lymphoma

Peripheral T-cell lymphomas (PTCLs) are regarded as diffuse proliferations. We describe an unusual paracortical nodular growth pattern in four nodal PTCLs that were initially interpreted as atypical lymphoid hyperplasia in three patients and small B-cell lymphoma with plasmacytic differentiation in a fourth. The nodules were vague to easily discernible and produced minimal to partial architectural distortion. Sinuses were often open, and scattered cortical lymphoid follicles with atretic to hyperplastic germinal centers were present. Clusters of tumor cells abutted some follicles in all cases, and in one case they exhibited focal T-zone expansion. Hypervascularity was not prominent, but a few nodules surrounded epithelioid venules, imparting an angiofollicular appearance. The nodules were composed primarily of small lymphocytes with irregular nuclei admixed with scattered large transformed cells, both cell types having clear cytoplasm. Paraffin immunoperoxidase showed that the nodules were composed of T cells. Dendritic cell networks were present only in follicular centers. Southern blot analysis found T-cell receptor gone rearrangements and a germline immunoglobulin gene configuration in all four nodes. These paracortical clear cell nodules of clonal T cells may be a special type of PTCL. Alternatively, they may represent early loci of lymphoma or they may be a subgroup of T-zone lymphoma. Paracortical nodular PTCL must be differentiated from atypical hyperplastic lesions and some B-cell lymphomas.