Morphological appearance of tumor vasculature of B16.F10 melanoma growing subcutaneously: immunohistochemical detection of CD31. Tumors were harvested at three different growth stages, based on tumor volumes as depicted in (e) (mean of 3 mice per group ± SEM). Vascular morphology differed per tumor growth stage, presenting vessels with increasing lumen size in intermediate and large tumors next to the presence of small vascular profiles, while small tumors were characterized by only small vessels that were generally lacking a visible lumen (Magnification 100x).