Veterinary Pathology Division, Department of Comparative Biomedical Sciences, Faculty of Veterinary Medicine, University of Teramo, Italy.
Vet Pathol. 2013 Mar;50(2):226-33. doi: 10.1177/0300985812456213. Epub 2012 Aug 3.
The histologic classification of canine perivascular wall tumors (PWTs) is controversial. Many PWTs are still classified as hemangiopericytomas (HEPs), and the distinction from peripheral nerve sheath tumors (PNSTs) is still under debate. A recent histologic classification of canine soft tissue sarcomas included most histologic types of PWT but omitted those that were termed undifferentiated. Twelve cases of undifferentiated canine PWTs were evaluated by transmission electron microscopy. The ultrastructural findings supported a perivascular wall origin for all cases with 4 categories of differentiation: myopericytic (n = 4), myofibroblastic (n = 1), fibroblastic (n = 2), and undifferentiated (n = 5). A PNST was considered unlikely in each case based on immunohistochemical expression of desmin and/or the lack of typical ultrastructural features, such as basal lamina. Electron microscopy was pivotal for the subclassification of canine PWTs, and the results support the hypothesis that canine PWTs represent a continuum paralleling the phenotypic plasticity of vascular mural cells. The hypothesis that a subgroup of PWTs could arise from a pluripotent mesenchymal perivascular wall cell was also considered and may explain the diverse differentiation of canine PWTs.
犬血管外膜肿瘤 (PWT) 的组织学分类存在争议。许多 PWT 仍被归类为血管外皮细胞瘤 (HEPs)，与周围神经鞘肿瘤 (PNSTs) 的区别仍存在争议。最近的犬软组织肉瘤组织学分类包括大多数 PWT 的组织学类型，但排除了那些被称为未分化的肿瘤。对 12 例未分化的犬 PWT 进行了透射电镜评估。超微结构发现支持所有病例均起源于血管外膜壁，具有 4 种分化类型：肌周细胞 (n = 4)、肌成纤维细胞 (n = 1)、成纤维细胞 (n = 2) 和未分化 (n = 5)。根据结蛋白的免疫组织化学表达和/或缺乏典型的超微结构特征（如基膜），每种病例均不太可能为 PNST。电镜对于犬 PWT 的亚分类至关重要，结果支持犬 PWT 代表与血管壁细胞表型可塑性平行的连续体的假说。还考虑了 PWT 的一个亚组可能来自多能间充质血管外膜壁细胞的假说，这可能解释了犬 PWT 的多样化分化。
