Updated Kiel classification for lymphomas

Controversies and Considerations in the Diagnosis of Primary Cutaneous CD4+ Small/Medium T-Cell Lymphoma

Context.—Primary cutaneous CD4+ small/medium T-cell lymphoma is a provisional and controversial entity with a broad differential diagnosis. Despite being an uncommon lymphoma, it is a frequent diagnostic consideration in cutaneous biopsies with a dense lymphoid infiltrate because it shows overlapping features with reactive lymphoid hyperplasia (pseudolymphoma) and a variety of other primary cutaneous and systemic lymphomas. However, proper classification of this process is important for determining patient prognosis and treatment options.

Objective.—To review the clinical, morphologic, immunophenotypic, and genetic features of primary cutaneous CD4+ small/medium T-cell lymphoma and contrast those features with entities in the differential diagnosis.

Data Sources.—Applicable literature will be reviewed with emphasis on current controversies and distinguishing characteristics.

Conclusions.—Although many consider primary cutaneous CD4+ small/medium T-cell lymphoma to be indistinguishable from reactive lymphoid hyperplasia/pseudolymphoma, it can be differentiated from other primary cutaneous and systemic lymphomas. Patients with solitary lesions of primary cutaneous CD4+ small/medium T-cell lymphoma generally have an excellent prognosis. Nevertheless, a subset of patients who have been reported to meet criteria for this lymphoma have followed a more-aggressive course; however, those patients show some differing clinical, morphologic, and immunophenotypic features.

An immunohistochemical study of spontaneous lymphomas in the C57B1/10J mouse

Immunocytochemistry was used to examine 26 cases of composite lymphoma in the mouse mesenteric lymph node. The diagnosis was made by light microscopic criteria. A selection of polyclonal antibodies to light (Kappa and Lambda) and heavy chain (IgD, IgM, IgC, IgA, IgE) antigens was used together with three monoclonal antibodies to T cells, B cells (HLA-DR) and macrophages. Twenty lymphomas were classified as B cell and six as T cell. The B cells were subdivided into IgM and IgD (five), IgD (five), IgM (three) and IgA (one), three undifferentiated and, in three, there was insufficient tissue for further typing. There did not appear to be any correlation between the morphological appearance and the immunophenotype.