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. The purpose of this study was to revise clinical presentation, cytology, histopathology, and immunohistology of canine cutaneous PWT with cytology typical of canine HEP. Diagnosis was established on the basis of vascular growth patterns (staghorn, placentoid, perivascular whorling, bundles from media) and immunohistology, including 7 smooth muscle markers and the cell membrane ganglioside of unknown origin recognized by the antibody 3G5 (CMG-3G5). Twenty cases were included. Ages ranged from 6 to 13 years; 12 dogs were males and 8 were females, and there was a prevalence of crossbreeds. Tumors arose from a single site with preferential acral location (10/20). Cytology revealed moderate to high cellularity in all cases, cohesive groups of cells (19/20), capillaries (18/20), and bi- to multinucleated cells (18/20). Six myopericytomas, 5 angioleiomyomas, 2 angioleiomyosarcomas, 2 HEP, 1 angiofibroma, and 1 adventitial tumor were identified. A definitive diagnosis was not possible in 3 cases. Smoothelin, heavy caldesmon, desmin, myosin, calponin, and CMG-3G5 were the most valuable markers to differentially diagnose canine PWT. Similar to reports in humans, canine HEP embodied a spectrum of neoplastic entities arising from different vascular mural cells. Before canine PWTs are assimilated into one prognostic category, a consistent classification and characterization of their biology is necessary. As proposed in humans, HEP should also be considered a diagnosis of exclusion in dogs.

Objective-To evaluate recurrence rate and disease-free interval (DFI) of dogs with low-grade soft tissue spindle cell sarcoma of the extremities treated by marginal excision. Study Design-Retrospective study. Animals-Dogs (n ¼ 35) with soft tissue low-grade spindle cell sarcoma. Methods-Medical records were reviewed and dogs that had marginal surgical resection of lowgrade soft tissue spindle cell sarcoma at or distal to elbow and stifle were included. Results-Histopathologic margins were dirty (12 dogs), clean but close (12), and clean (11). Followup after surgery occurred from 210 to 2202 days (minimum, 180 days). Local recurrence and metastatic rates were 10.8% and 0%, respectively. Median DFI and survival time were not reached, because o50% of dogs died of disease-related events. Mean DFI and mean survival time were 697.8 days (95% CI: 559.7-836 days) and 703.5 days (95% CI: 566.6-840.5 days), respectively. There were no significant differences among survival functions stratified by histologic margins. Conclusion-Marginal surgical excision without adjuvant treatment of low-grade soft tissue spindle cell sarcoma of the extremities results in a low local recurrence rate. Clinical Relevance-Low-grade spindle cell sarcomas located at or distal to the elbow and stifle joints can be excised without need for wide or radical surgery. r

Objective -To report the outcomes associated with sentinel lymph nodes (SLNs) detection and extirpation guided by radionuclide and methylene blue injections in dogs with cutaneous and subcutaneous mast cell tumors (MCTs).Study Design -Clinical prospective cohort study. Animals -30 client-owned dogs with MCTs amenable to wide-margin excision, without evidence of distant metastasis and abnormal regional lymph nodes (RLNs).Methods -Technetium-99m and methylene blue were injected peritumorally. Dogs underwent pre-operative gamma camera scintigraphy, and an intraoperative gamma probe guided SLN extirpation. Outcomes included technical and surgical complications, number of SLNs, SLNs location respecting the expected RLN, and histopathology results.Results -SLN mapping was applied to 34 MCTs in 30 dogs without any complication.SLNs were not identified in 3/34 tumors, all with previous scar tissue. SLNs did not correspond to expected RLNs in 19/30 (63%) tumors. Histological examination confirmed an early or overt metastasis in 32/57 (56%) SLNs extirpated.Conclusion -SLN mapping and biopsy with radionuclide and injection of methylene blue was associated with low morbidity and allowed detection of SLNs in dogs with MCT at first presentation without scar tissue.Clinical significance -Incorporation of SLN mapping and extirpation allows for a personalized staging approach in dogs with MCT. The presence of scar tissue in dogs with recurrent tumors seems to be a limitation for SLN mapping with this technique.

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Lymph node (LN) metastasis in canine cutaneous mast cell tumours (cMCTs) is a well-known negative prognostic factor. The role of lymphadenectomy in the treatment of stage II disease remains controversial because of its uncertain therapeutic benefit. Aim of this retrospective study was to investigate the impact of lymphadenectomy on tumour control and survival for dogs with stage II cMCTs. Dogs with firstly occurring, histologically confirmed cMCT with LN metastasis undergoing resection of the primary tumour and medical treatment thereafter were retrospectively enrolled. Dogs were classified into two groups: LN sampling (LNS; diagnosis of metastasis obtained by cytology) and regional LN dissection (LND; diagnosis obtained by histopathology). To determine the therapeutic value of lymphadenectomy, the characteristics of recurrence (local, nodal and distant) and survival were compared between groups. Evaluated outcome variables included signalment, anatomic location, diameter, ulceration, substage, surgical margins, Patnaik grading, Kiupel grading and medical treatment. Overall, 152 dogs were included: 81 underwent LND as part of primary surgery and 71 LNS. The median follow-up time was 409 days for LND group and 620 days for LNS group. On univariable analysis, the risk of developing local, nodal or distant relapse was significantly higher in the LNS group compared with LND (P < 0.001). On multivariable analysis, the risk of tumour progression and tumour-related death were 5.47 and 3.61 times higher in the LNS group, respectively (P < 0.001). Regional lymphadenectomy may have therapeutic value and improve prognosis in dogs with stage II cMCTs undergoing surgical removal of the primary tumour and medical treatment.

Metastasis to regional lymph nodes (RLNs) in dogs with cutaneous mast cell tumour (cMCT) has been correlated with shortened survival time and higher risk of spread to distant sites. In the present study, extirpation of non-palpable or normal-sized RLNs was included in the surgical management of cMCT in dogs. Correlations between histological nodal status (HN0-3) and tumour variables were analysed. Ninety-three dogs with single cMCT without distant metastasis that underwent wide surgical excision of the primary tumour and extirpation of non-palpable or normal-sized RLN were included. The association between HN (HN0 vs HN > 0; HN0-1 vs HN2-3) and tumour variables (site, longest diameter, ulceration, 3-tier and 2-tier histological grades) was analysed by a generalized linear model with multinomial error. Then, 33 (35.5%) RLNs were HN0, 14 (15%) were HN1, 26 (28%) were HN2 and 20 (21.5%) were HN3. The presence of positive (HN > 0) RLN was significantly associated with cMCT larger than 3 cm. No other association was statistically significant. Non-palpable/normal-sized RLN in dogs with cMCT can harbour histologically detectable metastatic disease in nearly half of the cases. Extirpation of the RLN should always perfomed to obtain a correct staging of the disease, even in the absence of clinical suspicion of metastasis. Further studies should evaluate the possible therapeutical effect of the tumour burden reduction obtained by exrtipartion of a positive RLN.

Background: In the clinical staging of cutaneous mast cell tumors (cMCT), the diagnosis of metastasis is controversial based on cytological examination of lymph nodes, spleen, liver, bone marrow, and blood.Objectives: To define the prognostic role of ultrasound-guided cytology of spleen and liver in cMCT. The results of cytological evaluation were compared in relation with survival time.Animals: Fifty-two client-owned dogs with a diagnosis of cMCT. Methods: Selection of cases was based on cytological evaluation of liver and spleen to detect infiltration at distant sites. The Kaplan Meier method was used to compare survival in dogs with and without infiltration of spleen and liver (log-rank test P o .05).Results: Ten dogs with cMCT had mast cell infiltration of spleen, liver, or both and 4 of these dogs had involvement of the regional lymph nodes. The majority of dogs had 2 or more ultrasonographically abnormal findings simultaneously in spleen and liver. Nine dogs had grade II cMCT, and 1 had grade III cMCT. Dogs with positive evidence of mast cell infiltration to spleen, liver, or both had shorter survival times (34 versus 733 days) compared with dogs negative for mast cell infiltration at distant sites.Conclusion and Clinical Importance: Dogs with evidence of mast cell infiltration at distant sites have a shorter survival times than dogs without evidence of infiltration at distant sites. This study suggests that cytology of spleen and liver is indicated either for ultrasonographically normal or for ultrasonographically abnormal spleen and liver in dogs with cMCT.

Absence of the aforementioned combination of variables at diagnosis may help identify dogs with lymphoma that will not survive > 2 years. Other types of neoplasia, in particular osteosarcoma, may develop in long-term-surviving dogs.