RESUMEN
Cutaneous lymphomas are low grade malignant neoplasms with favourable prognosis. Those related to the germinal centre with nodular pattern may be: follicular lymphomas (LFC) or extranodal marginal zone B-cell lymphomas (LMC). They are difficult to tell apart, and from reactive processes like cutaneous follicular hyperplasia and cutis immunocytomas. The objective of this study was to check the incidence and the value of both histology and immunohistochemistry in differential diagnosis. Fifty six patients with cutaneous lymphomas were selected within the period 1995-2004. The biopsies were studied with hematoxilin eosin and immunohistochemistry. Thirty two out of the fifty six cutaneous lymphoid infiltrates were of T origin (57.1%) and twenty four of B origin (42.8%), ten out of this last figure (17.7%) were lymphoid processes with nodular pattern Four LFC, three LMC and three HLC were diagnosed. Convergent follicles with scarce mantle and germinal centres with monomorph celullarity were observed in the LFC. Among the LMC, follicles with prominent mantle and nests of monocitoid cells in the mantle, interfollicular zone and in the germinal centers observed. In the HLC macrophages with detritus were found in the germinal centers. LFC showed: CD20 (+), CD 10 (+), bcl-2 (+) or (-), and bcl-6 (+) in the follicle and in the interfollicular area. LMC showed: CD 20 (+), bcl-2 (-), CD 10 (+/-), and bcl-6 (+) in the follicle, and bcl-2 (+), CD10 (-/+) and bcl-6 (-) in the interfollicular area. The HLC results were: bcl-2 (-), bcl-6 (+) and CD 10 (-) in the follicle and bcl-2 (+), bcl-6 (-) and CD 10 (-) in the interfollicular zone. We conclude that lymphoid B cell processes with nodular pattern are unusual. Histology and immunohistochemistry proved to be useful in the differential diagnosis of these lymphomas, and for differentiating these from lymphoid hyperplasias or non tumoral hyperplasias.