Alkaline phosphatase activity in non-Hodgkin's lymphomas and pseudolymphomas of the skin.

Alkaline phosphatase enzyme activity was studied histochemically in 60 non-Hodgkin lymphomas and 10 pseudolymphomas of the skin. Among the 37 B-cell lymphomas, membrane-bound alkaline phosphatase activity was demonstrated in 8 cases. In none of the 23 cutaneous T-cell lymphomas studied could membrane-bound alkaline phosphatase be detected. Among the pseudolymphomas, 2 cases revealed alkaline phosphatase activity. It was not possible to draw any particular clinically significant conclusions from the membrane-bound alkaline phosphatase reactions. Looking for the microenvironmental conditions of lymphoproliferative processes in the skin, alkaline phosphatase-positive capillaries were seen predominantly in the T-cell lymphomas. The stromal reaction showing a proliferation of alkaline phosphatase-positive fibroblasts was more pronounced in cutaneous B-cell lymphomas. In conclusion, membrane-bound alkaline phosphatase in lymphoproliferative processes in the skin, as in the lymph node, characterize a distinct group of B lymphocytes related to follicle center cells. The clinical relevance of this finding remains to be determined.