Morphometric study of primary cutaneous germinal center cell lymphomas

Background. Primary cutaneous germinal center cell lymphomas (PCGCCL) are B‐cell neoplasias; most are mixed cell type, composed of small and large cleaved cells and large noncleaved cells (centrocytes and centroblasts). Because of the significant pleomorphism of the cells, which ranged in size from small elements with indented nuclei to larger ones with multilobulated vesiculous nuclei, histopathologic examination of PCGCCL of mixed cell type has the worst degree of histologic interobserver reproducibility. Methods. In this study, the authors determined whether the light microscopic morphologic classification criteria applied in quantifying cleaved and noncleaved cells in these lymphomas are substantiated by morphometric analysis and have good reproducibility in differentiating the various cell subsets. They used an image analyzer (IBAS 2000, Zeiss Kontron, Munich, Germany) to study 17 centroblastic/centrocytic and centroblastic follicular and/or diffuse primary cutaneous lymphomas. Results. The data obtained showed morphometric differences between the follicular and diffuse patterns of neoplastic cells. In follicular neoplasms, the cells tend to be smaller, more cleaved, and more monomorphic than those observed in the diffuse forms. In all the follicular and diffuse cases, the authors observed a unimodal population with a wide peak composed of cells with intermediate morphometric features that cannot be labeled properly. Conclusions. These data underline the considerable overlap of nuclear parameters of lymphocytes between the subtypes of cells in cutaneous mixed small and large cell lymphoma, making the Kiel classification and Working Formulation unsuitable for this kind of neoplasia and supporting revision of classification criteria in cutaneous germinal center cell lymphomas. Cancer 1992; 70:1905‐1910.