Recent advances in the understanding of cutaneous lymphoma *

Summary Three hundred and sixteen patients with cutaneous lymphoreticular proliferations were studied using enzyme‐cytochemical and immunological techniques. Cell typing was performed using enzyme histochemistry, whilst B‐cell and T‐cell differentiation was achieved using surface markers, resetting and other techniques. These findings were then correlated with histopathology and cytomorphology. In the light of these data, the clinical, histological and cytological features of cutaneous lymphomas have been re‐interpreted and classified. The principal findings were as follows: (1) Historically in the skin a T‐cell, B‐cell and a non B‐/non T‐cell pattern can be differentiated. (2) According to the Kiel classification malignant lymphomas of low grade malignancy (small lymphoid cells) and of high grade malignancy (large lymphoid cells) can be differentiated; further sub‐classification is made into B‐cell and T‐cell types. (3) Tumours formerly diagnosed as malignant reticulosis and as reticulosarcoma of the skin need redefinition. Based on cytological criteria various sub‐types can now be differentiated. (4) Malignant lymphomas with primary skin manifestations of both B‐cell types and T‐cell types have an almost identical incidence.