Subcutaneous spindle cell tumours characterized by whorling growth patterns are common in dogs and are identified as a distinct entity. These tumours were misnamed as hemangiopericytomas (HPCs) because of some minor morphological parallels with their human counterparts. In veterinary medicine, the cell of origin of HPC has been under debate for a long time. Some authors have suggested a perivascular origin while others a perineural one. The evidence of the orientation of the neoplastic cells around the vessels and the expression of contractile proteins supported a perivascular origin while S100 expression and an inconsistent vascular connection supported a perineural origin. Despite the morphological similarities with peripheral nerve sheath tumours in humans, the perineural origin was supported mainly by the expression of markers with low specificity. On the contrary, the majority of studies have supported the perivascular origin of ‘old’ canine HPC. Since a variable degree of myoid‐pericytic differentiation was described, the term perivascular wall tumours (PWTs) were suggested to substitute HPC. Once the diagnostic criteria of PWTs were defined, the clinical behaviour and prognostic variables were investigated, demonstrating differences as compared with the group of canine soft tissue sarcomas (STSs) in general. PWTs are less aggressive, mostly locally invasive, and rarely metastasizing. Their behaviour seems to be less influenced by histological grade, suggesting that canine STSs are heterogeneous. The study of the biological behaviour of specific STS tumour types may be valuable in detecting differences which have passed unnoticed when STSs have been studied concomitantly.

中文翻译：

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犬皮下涡旋肿瘤的有争议的组织学分类：通往血管周壁肿瘤的途径。

以whorling生长方式为特征的皮下梭形细胞瘤在狗中很常见，被鉴定为不同的实体。这些肿瘤因与人类对应物的形态学上的微小相似而被误称为血管内皮细胞瘤（HPC）。在兽医学中，HPC的起源细胞已经争论了很长时间。一些作者提出了血管周围起源，而另一些则提出了神经周围起源。血管周围肿瘤细胞的方向和收缩蛋白表达的证据支持血管周起源，而S100表达和不一致的血管连接支持神经周起源。尽管与人类周围神经鞘瘤的形态相似，周围神经起源主要是由低特异性标志物的表达所支持。相反，大多数研究都支持“老”犬HPC的血管周围起源。由于描述了不同程度的肌-周细胞分化，建议用术语血管周壁肿瘤（PWTs）代替HPC。一旦确定了PWT的诊断标准，就研究了临床行为和预后变量，与一般的犬软组织肉瘤（STS）组相比，显示出差异。PWT的侵袭性较小，主要是局部侵袭性的，很少转移。它们的行为似乎受组织学等级的影响较小，表明犬的STS是异质的。