Microcirculation density and maturity in uterine and soft tissue leiomyosarcomas: an immunohistochemical study

The role of angiogenesis as a hallmark of tumor progression has been poorly explored in leiomyosarcoma, a rare but aggressive mesenchymal malignancy. We aimed to characterize microvessel distribution and morphology - including pericyte coverage - in a retrospective series of leyomiosarcomas of the soft tissues and the uterus. 41 whole-block tumor slides from formalin-fixed paraffin-embedded tissues were immunostained for endothelial-specific marker CD31 and microvessel density was quantified by assigning a grade to the frequency of CD31 positive microvessels. Vessel morphology and pericyte coverage were investigated by double-labeling for CD31 and either PDGFRβ, αSMA, desmin, CD90, or CD146. We found that microvessel density correlated with tumor grade in leiomyosarcoma of soft tissues, in analogy with what has been established in several types of carcinoma. This did not apply to uterine leiomyosarcoma, possibly due to the abundant myometrial vascularization. The evaluation of perivascular cell markers related to vessel stability revealed immature microvascular networks with aberrant pericyte coverage, irrespective of tumor origin or grade. Our observations substantiate the role of angiogenesis in the progression of soft tissue leiomyosarcoma. A multiple-marker approach to the assessment of pericyte coverage can identify different profiles of vessel immaturity correlated with tumor grade.