Читать книгу Veterinary Surgical Oncology - Группа авторов - Страница 153

Perivascular wall tumors (PWTs) are defined as neoplasms deriving from mural cells of blood vessels, excluding the endothelial lining. The spectrum of human cutaneous PWT includes glomus tumor, hemangiopericytoma (HEP), myopericytoma, angioleiomyoma/sarcoma, angiomyofibroblastoma, and angiofibroma (Avallone et al. 2007).

PWTs commonly arise in soft tissue. Their histopathological features are quite similar to those of canine malignant PNSTs, making their differential diagnosis challenging. Suzuki et al. suggest that NGFR and Olig2 are useful to distinguish between PWTs and malignant PNSTs as PWT cells displayed significantly weaker immunoreactivity than MPNSTs to these markers (Suzuki et al. 2014).

In cases of undifferentiated canine PWTs further evaluation has been reported by transmission electron microscopy. By electron microscopy, ultrastructural findings support a perivascular wall origin for all cases with 4 categories of differentiation: myopericytic, myofibroblastic, fibroblastic, and still undifferentiated (Palmieri et al. 2013).

Proteins of the VEGF‐, PDGFB‐, and bFGF‐mediated pathways have been reported to be highly expressed in 47.5–76.5 %, and in 10–35% of TGFβ1‐ and COX2‐mediated pathways of PWTs (Avallone et al. 2015). No association with the Ki67 labeling index was found in this study. Blockade of tyrosine kinase receptors after surgery could represent a promising therapy with the aim to reduce the PWT relapse rate and prolong the time to relapse (Avallone et al. 2015).

PWT can locally recur after a long time after surgery. Recurrence was reported in 2, 8, 20, and 24% at six months, one, two, and three years, respectively. Size of the tumor was a significant prognostic factor. An early diagnosis of PWT associated with small tumor size (<5 cm) and clean surgical margins ensures a good prognosis independently of histological grade (Stefanello et al. 2011). Major prognostic factors for perivascular wall tumors reported by Avallone et al. (2014) are tumor size, depth of growth, and pathological profiles. Smoothelin, heavy caldesmon, desmin, myosin, calponin, and CMG‐3G5 were the most valuable markers to differentially diagnose canine PWT (Avallone 2007).

Hemangiopericytomas (HEPs) are derived from pericytes, spindle cells surrounding blood vessels. Distinguishing these pericytes from endothelial cells, fibroblasts, and other spindle cells surrounding blood vessels is difficult based on morphologic and immunophenotypic assessment. Canine HEP has been proposed to be a diagnosis of immunohistochemical exclusion (Schulman et al. 2009; Mazzei et al. 2002; Williamson and Middleton 1998). The biological behavior of HEPs resembles that of PNSTs, and they stain similarly positive for the histochemical marker s100 (Chijiwa et al. 2004). Reported prevalence in dogs varies from 2 to 7% (Goldschmidt and Shofer 1992; Kaldrymidou et al. 2002; Mukaratirwa et al. 2005; Pakhrin et al. 2007), although they may have been formerly over diagnosed. The tumors are predominantly located on the extremities; however, other regions including the perineal area have been described. Only one case of HEP is reported in a cat (Baldi and Spugnini 2006). HEPs grow slowly and are locally aggressive because of infiltration into the surrounding tissues. Dogs with HEP showed higher serum VEGF levels compared to the patients with malignant PNSTs (De Quieroz et al. 2013). In a study by Stefanello et al. (2008), 35 dogs with marginal excision of low‐grade spindle cell sarcoma incurred a local recurrence rate of 10.8% and a metastatic rate of 0% (Avallone et al. 2007; Bostock and Dye 1980; Chijiwa et al. 2004; Fossum et al. 1988; Graves et al. 1988; Mayr et al. 1990; Stefanello et al. 2008).