Norrby K, Ridell B. Tumour-type-specific capillary endothelial cell stainability in malignant B-cell lymphomas using antibodies against CD31, CD34 and Factor VIII. APMIS 2003;111:483–9. The microvessel density (MVD) was assessed in lymph nodes infiltrated by diffuse large B-cell lymphomas, mantle cell lymphomas, chronic lymphatic leukemia and follicular lymphomas, and in lymphadenitis. Serial sections of formalin-fixed and paraffin-embedded tissue were stained with antibodies against CD31, CD34 or Factor VIII. Using light microscopy and computerised image analysis, the number and size of individual immunostained vessel profiles within a preselected area size range corresponding to capillaries, postcapillary venules, small collecting venules and small arterioles were determined. A significantly larger number of vessels were registered following staining with anti-CD34 than with anti-CD31 or anti-Factor VIII. Moreover, among the smallest capillary-sized vessel profiles in all lesion types, there was a selective relative loss of stainability of anti-CD31 and anti-Factor VIII, resulting in a substantial total loss of visualised capillary-sized vessels compared with anti-CD34. In fact, the number of non-detected capillaries following staining with anti-CD31 and anti-Factor VIII was significantly tumour type specific. These findings influence how we evaluate MVD data in B-cell lymphomas and possibly also other tumour types, as well as data relating to capillary endothelium-related functional variables of proliferation, apoptosis and maturation when different double-labelling immunohistochemical techniques are used and different tumour types are analysed.