Canine vascular neoplasia--histologic classification and inmunohistochemical analysis of 221 tumours and tumour-like lesions

Current understanding of comparative pathology and prospective research approaches for canine hemangiosarcoma

Hemangiosarcoma (HSA) is a malignant tumor originating from endothelial cells. HSA typically develops in dogs, but is rare in other animals, including humans. Although surgery and chemotherapy are conventional treatments for HSA, neither treatment can significantly improve patient prognosis. To develop novel and effective therapeutics, a deeper understanding of HSA pathogenesis must be acquired. However, the limited research tools for HSA have been unable to make a breakthrough; therefore, it is crucial to widely utilize or establish novel research tools such as patient-derived xenograft models, organoids, and chicken embryo xenograft models. The pathogenesis of the human counterpart of HSA, angiosarcoma (AS), also remains incompletely understood, preventing the extrapolation of findings from humans to dogs, unlike other diseases. In this review, we summarize the clinicopathological and morphological features of HSA, and then we discuss the current understanding of the molecular pathology of HSA. Finally, we highlight promising research tools that may accelerate HSA basic research toward developing novel therapeutics. We also briefly summarize AS to help researchers comprehend HSA from the perspective of comparative pathology.

Tumor-associated macrophages in canine visceral hemangiosarcoma

Canine hemangiosarcoma (HSA) is a highly malignant tumor derived from hematopoietic stem cells and commonly occurs in visceral organs or skin. Visceral HSAs are particularly aggressive and progress rapidly despite multimodal treatment. Tumor-associated macrophages (TAMs) play a central role in carcinogenesis, tumor progression, and metastasis in humans and murine models. In this retrospective study, we investigated the prevalence and phenotype of TAMs in privately owned, treatment-naïve dogs with naturally occurring HSA. We used CD204 as a general macrophage marker and CD206 as a marker for M2-polarized macrophages. Formalin-fixed paraffin-embedded tissues from HSAs in the spleen (n = 9), heart (n = 6), and other locations (n = 12) from 17 dogs were sectioned and immunohistochemically labeled with CD204 and CD206 antibodies. The mean number of log(CD204)- and log(CD206)-positive cells and the ratio of log(CD206/CD204)-positive cells were compared with normal surrounding tissues and between tumor locations. There were significantly more macrophages and M2 macrophages, and a higher ratio of M2 macrophages to total macrophages in tumor hot spots (P = .0002, P < .0001, and P = .0002, respectively) and in tumor tissues outside of hot spots (P = .009, P = .002, and P = .007, respectively) than in normal surrounding tissues. There were no significant differences between tumor locations, but there was a trend toward higher numbers of CD204-positive macrophages within the splenic tumors. There was no association between histological parameters or clinical stage and TAM numbers or phenotype. As in humans, TAMs in dogs with HSA have a predominantly M2-skewed phenotype. Dogs with HSA could serve as excellent models to evaluate new TAM-reprogramming therapies.

Urinary bladder hemangiosarcoma in a cat treated with partial cystectomy and adjuvant metronomic cyclophosphamide and thalidomide

Visceral hemangiosarcomas (HSA) are rare in cats and typically associated with aggressive biologic behavior and poor prognosis. A 4-year-old male neutered domestic shorthair cat was presented with a 3-month history of hematuria and stranguria; ultrasonography identified a large bladder mass. Complete excision was achieved by partial cystectomy. Histopathology and immunohistochemistry for von Willebrand factor confirmed HSA. The cat was treated using adjuvant cyclophosphamide, thalidomide, and meloxicam for 8 months. Abdominal ultrasonography repeated at 2 months and computed tomography repeated at 5 and 19 months after diagnosis showed no evidence of local recurrence or metastasis. The cat was alive at last follow-up (896 days). Although the cat described in this report experienced a more favorable prognosis compared to other visceral HSA locations, additional cases are needed to further understand the biological behavior of bladder HSAs and guide treatment decisions.

Histopathological Grading, Clinical Staging and CD 31 Expression of Canine Splenic Hemangiosarcoma

Canine hemangiosarcoma is a common, highly fatal tumor of older dogs, and predictors of survivability may provide clinically useful information. The objectives of this case series were to determine if a previously published tumor histological grading scheme, the level of tumor cellular atypia, clinical staging, or the level of CD 31 expression were useful for predicting the survival time in dogs with splenic hemangiosarcoma. Canine splenic hemangiosarcomas from 16 dogs were histologically graded, clinically staged, and assessed for CD 31 expression. Medical records were reviewed, the date of death was obtained, and survival data were analyzed statistically. Histopathological grading and clinical staging of canine splenic hemangiosarcomas, and the expression of CD 31 by the tumor cells were not significantly associated with the median survival time of the dogs in this study. However, strong expression of CD 31 by canine splenic hemangiosarcoma tumor cells was observed in dogs with short survival times, which warrants further studies to evaluate the potential prognostic value of CD 31 expression for the survival of dogs with splenic hemangiosarcoma.

Granulation tissue-type hemangioma in a 6-week-old puppy - a case report

BACKGROUND

Hemangioma is a well-known neoplasia in veterinary and human medicine. Several subtypes have been described and are distinguished based on their histologic appearance. The classification schemes of hemangiomas in human and veterinary medicine are different, and various purpose-based schemes can be found in the literature.

CASE PRESENTATION

A six-week-old puppy was presented that suffered from a neoplasia that extended to the musculature of the hind limb. After surgical excision, the mass was submitted for pathohistological examination. The mass was composed of endothelial cells forming vascular slits admixed with a fibrous stroma and spindle cells. Immunohistological examination was positive for factor VIII-related antigen and smooth muscle actin, supporting the diagnosis of hemangioma.

CONCLUSION

The final diagnosis of granulation tissue-type hemangioma was given due to the histological appearance of the neoplasia. Granulation tissue-type hemangioma is a rare subtype of hemangioma. In this case an uncommonly young dog was affected.

Extravascular papillary endothelial hyperplasia mimicking soft tissue sarcoma in 2 cats: a potential diagnostic pitfall

Papillary endothelial hyperplasia (PEH) is a rare soft tissue lesion arising from excessive reactive endothelial cell proliferation described in humans, dogs, and horses. PEH is considered a diagnostic challenge in humans, in which it is frequently misdiagnosed as angiosarcoma. We describe here PEH that developed at injection sites in 2 cats that were initially misdiagnosed as feline injection-site sarcoma by cytology and as subcutaneous angiosarcoma by histopathology. Morphologic features included sharp demarcation from surrounding tissues, and a layered microscopic architecture with an outer fibrous capsule from which emerged fibrovascular stalks covered by a monolayer of factor VIII-related antigen and CD31-positive flat-to-plump endothelial cells. Both lesions had a cystic core containing abundant erythrocytes and fibrin. PEH lesions did not recur in either case. Immunohistochemistry for α-smooth muscle actin and desmin demonstrated that the capsule was devoid of smooth muscle cells, excluding an intravascular origin. PEH in these cats was hypothesized to have developed extravascularly following trauma related to injection. We wish to provide awareness of PEH in domestic cats and of the risk of misdiagnoses leading to overtreatment.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Nonproliferative and Proliferative Lesions of the Dog

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions) Project (www.toxpath.org/inhand.asp) is a joint initiative of the societies of toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in most tissues and organs from the dog used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions, lesions induced by exposure to test materials, and relevant infectious and parasitic lesions. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

Identification of serum microRNAs with differential expression between dogs with splenic masses and healthy dogs with histologically normal spleens

OBJECTIVE

To identify differential microRNA (miRNA) expression in dogs with splenic hemangiosarcoma, splenic hematoma, and histologically normal spleens.

ANIMALS

Dogs with splenic hemangiosarcoma (n = 10), splenic hematoma (n = 5), and histologically normal spleens (n = 5).

PROCEDURES

Splenic tissue and serum samples were collected from dogs with splenic masses (ie, hemangiosarcoma or hematoma samples) and healthy control dogs (ie, control samples), and total RNA was extracted. Reverse transcription quantitative real-time PCR was performed with 28 miRNAs associated with hemangiosarcoma, angiosarcoma, or associated genes. Differential expression analysis was performed.

RESULTS

Control tissue and serum samples had similar miRNA expression patterns, and hemangiosarcoma tissue and serum samples did not. Hemangiosarcoma serum samples had higher expression than hemangiosarcoma tissue for 13 miRNAs and lower expression for 1 miRNA. Control tissue and hemangiosarcoma tissue had varying expressions for 12 miRNAs, with 10 more highly expressed in control samples and 2 more highly expressed in hemangiosarcoma samples. Five miRNAs (miR-214-3p, miR-452, miR-494-3p, miR-497-5p, miR-543) had significantly different expression in serum between dogs with splenic masses (ie, hemangiosarcoma or hematoma) and serum of dogs with histologically normal spleens, with higher expression in the serum of dogs with splenic masses for all 5 miRNAs.

CONCLUSIONS AND CLINICAL RELEVANCE

5 circulating miRNAs were identified that distinguished dogs with splenic hemangiosarcoma or hematoma from those with histologically normal spleens. These 5 miRNAs had higher expression in dogs with splenic masses, indicating upregulation of these circulating miRNAs occurs in these splenic disease states. These miRNAs may be useful as a noninvasive screening tool that uses serum to identify dogs with splenic masses.

An Angiomyomatous Hamartoma With Features of Vascular Transformation of Sinuses in the Mediastinal Lymph Node of a Beagle Dog

Two similar benign, nonneoplastic vascular lesions have been described in the lymph nodes of humans and animals: angiomyomatous hamartoma (AMH), which is characterized by the replacement of lymphoid tissue by blood vessels, smooth muscle, and fibrous tissue, and vascular transformation of sinuses (VTS), which is considered a reactive transformation of lymph node sinuses into capillary-like vascular channels. We hereby report a lesion with features common to both lesions in the mediastinal lymph nodes of a 1-year-old beagle dog in a 1-month toxicity study. Grossly, enlargement and red discoloration were observed, while microscopically, the lesion was characterized by effacement of the lymph node parenchyma with replacement by mature blood vessels, smooth muscle, and fibrous tissue, associated with lymphoid atrophy, which is consistent with AMH. However, multifocal areas of anastomosing or plexiform capillary-like channels lined by normal to slightly plump endothelium, similar to those described for VTS, were also present. Immunohistochemistry analysis revealed abundant positive staining for smooth muscle actin and endothelial cells (von Willebrand factor/factor VIII) and the absence of proliferation (Ki67). In conclusion, these lesions most likely represent a mixture of both AMH and VTS.

Spontaneous hemangioendothelial cell hyperplasia of the heart in a young ICR mouse

Spontaneous nonneoplastic proliferative lesions of the cardiac hemangioendothelium are extremely rare in humans and animals. Here, we describe a spontaneous hemangioendothelial cell hyperplasia in the heart of a 9-week-old male ICR mouse. The lesion was observed focally in the interventricular septum, with no compression of the surrounding tissues. In the lesion, a single layer of hemangioendothelial cells that had a polygonal shape with enlarged nuclei and plump cytoplasm closely lined surrounding widened capillary vascular spaces and cardiac muscles. There was little cellular atypia, and there were no multilayered endothelial cells. Immunohistochemical staining revealed that these cells were partly positive for factor VIII and CD31, hemangioendothelial cell markers, and negative for Ki-67. These features were consistent with those in aged female B6C3F₁ mice in the only report in mice of spontaneous cardiac hemangioendothelial cell hyperplasia. Therefore, this is the first report of spontaneous hemangioendothelial cell hyperplasia in the heart of a young mouse.

Cutaneous epithelioid hemangiosarcoma with granular cell differentiation in a dog: a case report and review of the literature

We report a case of cutaneous epithelioid hemangiosarcoma in a dog in which the majority of the neoplastic cells displayed histologic and ultrastructural features similar to those seen in granular cell tumors (GCTs). This intersection of hemangiosarcoma and granular cell change adds to the argument that GCTs are heterogeneous in histologic origin and underlines the fact that pathologists should not consider all GCTs as a single entity. The combination of histology in typical areas of the tumor with ultrastructural changes and the correct immunohistochemical markers can facilitate the accurate diagnosis of tumors with granular cell differentiation. Besides characteristic intracytoplasmic PAS-positive granules and ultrastructural proteinaceous accumulation within single membrane vesicles (presumably lysosomes and phagolysosomes), we suggest the following combination of markers for the diagnosis of granular cell angiosarcoma and/or hemangiosarcoma: vimentin positive, NSE and/or S100 negative, CD31 positive. We propose that the histologic granular appearance represents a metabolic defect of the neoplastic cells, which supports variability in cell origin for granular cell differentiation.

Does thalidomide prolong survival in dogs with splenic haemangiosarcoma?

OBJECTIVES

To investigate thalidomide as an adjuvant treatment for canine haemangiosarcoma.

MATERIALS AND METHODS

Fifteen dogs with splenic haemangiosarcoma, initially treated by splenectomy, were included. Following recovery from surgery, all dogs received thalidomide continuously until their death. Tumour stage was established using CT scans of the chest and abdomen immediately before starting thalidomide treatment and again three months later. Cause of death was confirmed by post mortem examination.

RESULTS

The median survival time of dogs receiving thalidomide was 172 days (95% confidence interval: 93 to 250 days). Five dogs (33% of the population receiving thalidomide) survived more than 1 year (range 458 to 660 days) after surgery. Dogs with stage 2 disease that received thalidomide also had a longer survival time than dogs with stage 3 disease (median survival time 303 versus 40 days). Of 15 dogs, 13 died from metastatic haemangiosarcoma.

CLINICAL SIGNIFICANCE

Treatment using thalidomide may improve survival of dogs with splenic haemangiosarcoma and should be considered a possible adjuvant therapy.

Cutaneous Angiolymphoid Hyperplasia in a Dog

A 5-year-old male miniature dachshund was presented with a dermal nodule on the left forelimb that increased to 5 mm in diameter over a 2-month period. Grossly, the nodule was firm, and both the external and cut surfaces were homogeneously pale pink in colour. Microscopically, the nodule was comprised of mainly plump endothelial cells and inflammatory cells; among the latter, lymphocytes were predominant, with few scattered plasma cells, mast cells and macrophages. Lymphoid follicles with germinal centres were often observed. Mitotic figures were not observed amongst the endothelial cells. Immunohistochemically, the endothelial cells were positive for vimentin, factor VIII-related antigen and CD31, and the surrounding cells were positive for smooth muscle actin. Lymphocytes expressed CD3 or BLA36. These findings led to a diagnosis of cutaneous angiolymphoid hyperplasia. To the best of our knowledge, this is the first report of a cutaneous proliferative disorder comprising an admixture of proliferating vascular endothelial cells and lymphocytic infiltration with follicle formation in a dog.

A comparison of microRNA expression profiles from splenic hemangiosarcoma, splenic nodular hyperplasia, and normal spleens of dogs

Background

Splenic masses are common in older dogs; yet diagnosis preceding splenectomy and histopathology remains elusive. MicroRNAs (miRNAs) are short, non-coding RNAs that play a role in post-transcriptional regulation, and differential expression of miRNAs between normal and tumor tissue has been used to diagnose neoplastic diseases. The objective of this study was to determine differential expression of miRNAs by use of RNA-sequencing in canine spleens that were histologically confirmed as hemangiosarcoma, nodular hyperplasia, or normal.

Results

Twenty-two miRNAs were found to be differentially expressed in hemangiosarcoma samples (4 between hemangiosarcoma and both nodular hyperplasia and normal spleen and 18 between hemangiosarcoma and normal spleen only). In particular, mir-26a, mir-126, mir-139, mir-140, mir-150, mir-203, mir-424, mir-503, mir-505, mir-542, mir-30e, mir-33b, mir-365, mir-758, mir-22, and mir-452 are of interest in the pathogenesis of hemangiosarcoma.

Conclusions

Findings of this study confirm the hypothesis that miRNA expression profiles are different between canine splenic hemangiosarcoma, nodular hyperplasia, and normal spleens. A large portion of the differentially expressed miRNAs have roles in angiogenesis, with an additional group of miRNAs being dysregulated in vascular disease processes. Two other miRNAs have been implicated in cancer pathways such as PTEN and cell cycle checkpoints. The finding of multiple miRNAs with roles in angiogenesis and vascular disease is important, as hemangiosarcoma is a tumor of endothelial cells, which are driven by angiogenic stimuli. This study shows that miRNA dysregulation is a potential player in the pathogenesis of canine splenic hemangiosarcoma.

Primary intrapelvic hemangiosarcoma in a dog

A 12-year-old, spayed female Schnauzer presented with constipation. A mass was observed in the pelvic cavity, and metastasis was not identified. Mass resection was performed through celiotomy with pubic osteotomy, and hemangiosarcoma was diagnosed. At 10 weeks post-operatively, the patient died of multiple metastasis. Primary intrapelvic hemangiosarcoma is rare in dogs.

Canine splenic haemangiosarcoma: influence of metastases, chemotherapy and growth pattern on post-splenectomy survival and expression of angiogenic factors

Splenic haemangiosarcomas (HSAs) from 122 dogs were characterized and classified according to their patterns of growth, survival time post splenectomy, metastases and chemotherapy. The most common pattern of growth was a mixture of cavernous, capillary and solid tumour tissue. Survival time post splenectomy was independent of the growth pattern; however, it was influenced by chemotherapy and metastases. Immunohistochemical assessment of the expression of angiogenic factors (fetal liver kinase-1, angiopoietin-2, angiopoietin receptor-2 and vascular endothelial growth factor A) and conventional endothelial markers (CD31, factor VIII-related antigen) revealed variable expression, particularly in undifferentiated HSAs. Therefore, a combination of endothelial markers should be used to confirm the endothelial origin of splenic tumours.

Massive haematoma formation associated with proximal popliteal artery haemangioendothelioma in a dog

A mixed breed dog presented with diffuse unilateral hind limb swelling, which ultrasound and cytology confirmed to be caused by severe haematoma formation. Multi-detector computed tomography (MDCT) angiography allowed distinct visualisation of an anomalous segment of the proximal popliteal artery, the presumed origin of the self-sustaining haematoma. Histopathology classified the malformed vessel as a haemangioendothelioma, a neoplasia of intermediate malignancy. Considering this as differential diagnosis to a neoplastic vascular alteration of high malignancy (such as haemangiosarcoma) might alter choice of treatment in future cases with similar clinical and imaging findings.