Retrospective study and immunohistochemical analysis of canine mammary sarcomas

Risk factor analysis and clinicopathological characteristics of female dogs with mammary tumours from a single-center retrospective study in Poland

This is a comprehensive retrospective study to characterize female dogs with canine mammary tumors (CMTs) using a dataset retrieved from the archives of the Division of Animal Pathology, Institute of Veterinary Medicine in Warsaw, and to identify prognostic factors. Clinical and histopathological data of 1447 dogs with CMTs were included. Malignant tumours were found in 83.3% (n = 1206), benign tumours in 11.7% (n = 169), and non-neoplastic lesions in 5.0% (n = 72) of dogs. Dogs most often had grade II carcinomas (38.2%, 215/562) of a single histological subtype (88.5%, 1281/1447), mostly simple carcinoma (35.3%, 510/1447). Dogs with a median age of 10 years significantly often had larger (≥ 3 cm) and malignant CMTs, whereas intact females had smaller tumours (median size 2.0 cm). However, the threshold value for the age of the dog in the differentiation of malignant and non-neoplastic/benign masses could not be determined. Most females were hormonally active (76.4%, 372/487). Hormonally active dogs significantly more often had multiple tumours. Multiple tumours were significantly smaller (median 2.5 cm) than single ones. Among pedigree dogs, small-breed dogs were mostly recorded (43%, 428/1006). Twelve breeds had an increased risk of CMTs, regardless of tumour behaviour, compared with the theoretical distribution of pedigree dogs in Poland. Four breeds were often affected only by malignant and other four breeds only by non-neoplastic/benign CMT. Large-breed dogs were significantly younger and affected by larger CMT (median 4 cm) compared with small- and medium-breed dogs. Ninety dogs with a malignant CMT and complete records were included in the full analysis of CMT-specific survival (CMT-SS) with a median follow-up time of 20.0 months. We showed that the timing of ovariohysterectomy in relation to mastectomy was significantly associated with grade, CMT-SS, and CMT-related death. We indicated the low diagnostic accuracy of palpation of regional lymph nodes (RLN) in the prediction of their metastatic involvement. By multivariable analysis, dogs with neoplastic emboli, tumour ulceration, and simple or complex carcinoma had a significantly higher risk of local recurrence. Tumour size > 3 cm was as a strong independent predictor of lung metastases. Compared with dogs with an easily separated localized tumour, dogs with a multiple/diffuse malignant CMT pattern had a fivefold higher risk of death. The risk of death was significantly higher in the presence of neoplastic emboli (~ fivefold) and tumour ulceration (~ fourfold). Furthermore, the presence of neoplastic emboli and large tumour size were independent predictors of CMT-related death.

Multi-organ metastases of primary chondrosarcoma of the mammary gland of a spayed Toy Poodle

We report the clinical and histopathological findings associated with multi-organ metastases of primary mammary chondrosarcoma in a 12-year-old spayed female Toy Poodle. At post-mortem examination, multifocal, sharply demarcated, grey-white to bright brown, round nodules of variable size were randomly distributed in the lungs, myocardium, liver, pancreas, spleen, intestinal tract and kidneys. Histologically, immature cartilage structures and primitive mesenchymal cells were seen in these organs. Neoplastic cells located in the cartilaginous basophilic extracellular matrix had cytoplasmic vacuolation and round vesicular nuclei and were stained with Safranin O and Alcian blue. To the best of our knowledge, this is the first report of a multi-organ metastatic chondrosarcoma that originated in the mammary gland of a dog.

Comparison of the anti-cancer activity of 5-aminolevulinic acid-mediated photodynamic therapy after continuous wave and pulse irradiation in different histological types of canine mammary sarcoma tumors

Canine mammary sarcoma tumors (CMST) are the most aggressive tumors with poor prognosis in dogs. Due to inadequate treatment options for CMST, recent studies have focused on alternative treatment strategies. We previously determined the optimized protocol of 5-ALA-based photodynamic therapy (PDT) in canine liposarcoma. However, its molecular mechanisms in the treatment of different histological types of CMST remain unclear.In this context, we, for the first time, assessed 5-aminolevulinic acid (5-ALA)-PDT-mediated anti-cancer activity and its molecular mechanism after continuous wave (CW) and pulse radiation (PR) on three different histological types (liposarcoma, chondrosarcoma, and osteosarcoma) of CMST cells by WST-1, Annexin V, ROS, acridine orange/propidium iodide staining, RT-PCR, and western blot analysis.Our findings showed that 5-ALA/PDT significantly suppressed the proliferation of CMST cells (p < 0.01) and induced apoptosis via increased ROS level and overexpression of Caspase-9 and Caspase-3 mRNA and cleaved protein levels in especially liposarcoma and chondrosarcoma cells following CW and PR irradiation at 9 J/cm2. However, the response of CMST cells to 5-ALA was different upon CW and PR irradiation due to differences in their origin.Collectively, our findings provided the first evidence that 5-ALA-based PDT could be used as an alternative treatment strategy, especially liposarcoma and chondrosarcoma. However, further in vitro and in vivo studies are required to elucidate the underlying molecular mechanism of the efficacy of 5-ALA in CMST cells at the molecular level.

Epidemiology of canine mammary tumours on the Canary Archipelago in Spain

BACKGROUND

Mammary gland tumours are the most frequently diagnosed tumours in the female dogs but just a few studies have analysed their epidemiology. Therefore, we set out to describe the epidemiology of canine mammary cancer in the Canary Archipelago, Spain. We analysed a pathology tumour registry (PTR) and identified 7362 samples obtained from 5240 female dogs resident on the Canary Archipelago during an 18-year period (2003-2020). Using a case-control study design, we compared mammary tumour affected dogs with the Canarian canine population registry in order to elucidate the breed associations for these tumours.

RESULTS

The frequency of a diagnosis of mammary tumours relative to all tumour diagnoses in female dogs decreased during the study period from 62.7% to 48.9%. Contemporaneously, the proportion of dogs diagnosed with mammary tumours who were also neutered increased from 13.6% to 26.9%. There was a negative correlation (R = -0.84) between these changes. Additional findings were that: the proportion of female dogs diagnosed with multiple tumours increased by 23.5% and that the proportion of malignant tumours 89.2% diagnosed has remained stable through the period. Benign mammary tumours were diagnosed at younger ages (9.2 years old) than carcinomas (9.7 years old) and sarcomas (10.4 years old). Epithelial mammary tumours were diagnosed at younger ages in entire female dogs. Samoyed, Schnauzer, Poodle, German Pinscher and Cocker Spaniel were the breeds with the highest odds-ratios (OR) in comparison with the reference (crossbreeds) while Miniature Pinscher, American Staffordshire Terrier, English Pointer as well as some local breeds such as the Canary Warren Hound and the Majorero had the lowest ORs.

CONCLUSIONS

This study provides a description of the changing epidemiology of canine mammary cancer in the Canary Archipelago over the last two decades. We found high rates of CMT with a significant predominance of malignant tumours. Exact risk factors are uncertain, but a combination of environmental, regional socioeconomic affecting human and their pets, and animal management factors are likely to play a part. Specifically, neutering was negatively associated with the proportion of epithelial mammary gland tumours and breeds native to the region were at lower risk of mammary tumours. A deeper analysis of all these factors will facilitate a deeper understanding of the epidemiology of mammary gland tumours in both the canine and the human population.

MicroRNA-21 expression, serum tumor markers, and immunohistochemistry in canine mammary tumors

BACKGROUND

Canine mammary tumors (CMTs) are one of the most common malignancies in dogs and are associated with significant mortality. Serum tumor markers and non-coding microRNAs have gained widespread popularity in human oncology studies. The present study has two aims, first one is to investigate the miR-21 expression compared with changes in serum tumor markers (CEA and CA15-3) in CMT. The second aim is to detect the immunohistochemistry markers as vimentin, P63, and -SMA in CMT.

METHODS

This study enrolled 17 female dogs: 10 with mammary tumors and seven controls without tumors. Blood samples were collected to measure miR-21, CEA, and CA 15-3, and histological samples were prepared for histological grading and immunohistochemistry.

RESULTS

CA 15-3 was elevated in all animals, whereas CEA levels showed no change compared with controls. miR-21 was upregulated 12.84-fold in animals with CMT. The most frequently recorded CMT was the mixed type. Myoepithelial cells were identified by P63 immunoreactivity, but not SMA. High expression of miR-21 was observed with positive vimentin immunoreactivity, indicating the mesenchymal origin of the tumor cells.

CONCLUSION

The present study showed that miR-21 was elevated to a greater extent than CA 15-3 (12.84-fold vs. threefold). Tumors that was positive for vimentin immunoreactivity was also associated with an elevation in the levels of miR-21, showing that miR-21 is released from mesenchymal cells. These findings support the hypothesis that miR-21 may be a more sensitive, noninvasive indicator for CMT.

Characterization of neoplastic cells outlining the cystic space of invasive micropapillary carcinoma of the canine mammary gland

BACKGROUND

Invasive micropapillary carcinoma (IMPC) is a rare malignant breast tumor and a variant form of invasive ductal carcinoma that is an aggressive neoplasm of the human breast and canine mammary gland. The importance of the tumor microenvironment in cancer development has gradually been recognized, but little is known about the cell types outlining the cystic space of canine IMPC. This study aimed to characterize the neoplastic cells outlining the cystic space of IMPC.

RESULTS

Immunohistochemistry (IHC), immunofluorescence (IF), superresolution and transmission electron microscopy (TEM) were used to assess the cell types in the cystic areas of IMPCs. Cells expressing the mesenchymal markers alpha-smooth muscle actin (αSMA), Vimentin, and S100A4 outlined the cystic space of IMPC. Furthermore, loss of epithelial cell polarity in IMPC was shown by the localization of MUC1 at the stroma-facing surface. This protein modulates lumen formation and inhibits the cell-stroma interaction. Immunohistochemical and IF staining for the myoepithelial cell marker p63 were negative in IMPC samples. Furthermore, associated with peculiar morphology, such as thin cytoplasmic extensions outlining cystic spaces, was observed under TEM. These observations suggested cells with characteristics of myoepithelial-like cells.

CONCLUSIONS

The cells outlining the cystic space of IMPC in the canine mammary gland were characterized using IHC, IF and TEM. The presence of cells expressing αSMA, Vimentin, and S100A4 in the IMPC stroma suggested a role for tumor-associated fibroblasts in the IMPC microenvironment. The reversal of cell polarity revealed by the limited basal localization of MUC1 may be an important factor contributing to the invasiveness of IMPC. For the first time, the cystic space of canine mammary gland IMPC was shown to be delimited by myoepithelial-like cells that had lost p63 expression. These findings may enhance our understanding of the cellular microenvironment of invasive tumors to improve cancer diagnosis and treatment.

Expression of transferrin receptor-1 (TFR-1) in canine osteosarcomas

Due to high rates of proliferation and DNA synthesis, neoplastic cells have higher requirements of iron than normal cells. For that reason, neoplastic cells have remodelled iron metabolism pathways, over‐expressing genes encoding for iron uptake proteins, among which Transferrin Receptor‐1 (TFR‐1). Accumulating evidence has proven that overexpression of TFR‐1 and high Iron concentration, are both widespread condition of cancer cells, both essential to tumour onset and progression. We studied TFR‐1 and PCNA immunohistochemical expression in fifteen (15) Canine osteoblastic osteosarcomas (COS). After immunohistochemical staining, counting of TFR‐1 positive cells by two independent observers showed that 85%–95% of neoplastic cells were strongly labelled at cytoplasmic level by anti‐TFR‐1 antibody in all examined COS. Furthermore, 70%–80% of neoplastic cells were positively labelled at the nuclear level by PCNA. Surprisingly, about 100% of intratumour vascular endothelial cells were also positive, whereas extratumour vascular endothelial cells were negative. The latter is an interesting finding, as TFR‐1 is usually not expressed in normal vasculature, with the exception of normal brain vascular endothelium, where it allows transport of transferrin, and thus iron, into tissues, suggesting a similar function here to support cancer growth. The early results presented highlight the relevance of TFR‐1 expression in canine OS, suggesting therapies involving both TFR‐1 and Iron metabolisms in dogs with osteosarcoma should be developed.

In vitro and in vivo effects of toceranib phosphate on canine osteosarcoma cell lines and xenograft orthotopic models

Canine osteosarcoma (OSA) is the most common primary malignant bone tumour in dogs, and it has a high metastatic rate and poor prognosis. Toceranib phosphate (TOC; Palladia, Zoetis) is a veterinary tyrosine kinase inhibitor that selectively inhibits VEGFR-2, PDGFRs and c-Kit, but its efficacy is not yet fully understood in the treatment of canine OSA. Here, we evaluated the functional effects of TOC on six OSA cell lines by transwell, wound healing and colony formation assays. Subsequently, two cell lines (Wall and Penny) were selected and were inoculated in mice by intrafemoral injection to develop an orthotopic xenograft model of canine OSA. For each cell line, 30 mice were xenografted; half of them were used as controls, and the other half were treated with TOC at 40 mg/kg body weight for 20 days. TOC inhibited cell growth of all cell lines, but reduced invasion and migration was only observed in Penny and Wall cell lines. In mice engrafted with Penny cells and subjected to TOC treatment, decreased tumour growth was observed, and PDGFRs and c-Kit mRNA were downregulated. Immunohistochemical analyses demonstrated a significant reduction of Ki67 staining in treated mice when compared to controls. The results obtained here demonstrate that TOC is able to slightly inhibit cell growth in vitro, while its effect is evident only in a Penny cell xenograft model, in which TOC significantly reduced tumour size and the Ki67 index without modifying apoptosis markers.

Canine Spindle Cell Mammary Tumor: A Retrospective Study of 67 Cases

Canine spindle cell mammary tumor (CSCMT) is an infrequent canine mammary tumor (CMT) composed of spindle or fusiform cells, which represents a challenge for pathologists and clinicians. Mammary tumors submitted for histopathology from 1998 to 2013 and compatible with CSCMTs were retrospectively selected. The tumors were diagnosed based on the hematoxylin and eosin (HE)-stained section; malignant tumors were graded using a canine soft tissue sarcoma grading scheme and a canine mammary tumor grading scheme, and they were further assigned a diagnosis based on immunohistochemistry (IHC) for pancytokeratin, cytokeratin 14, p63, calponin, vimentin, Ki-67, CD31, desmin, myosin, smooth muscle actin, glial fibrillary acidic protein, and S-100. The origin of the tumors was assessed as mammary, skin, or unknown. The prevalence of CSCMT was 1% of all CMTs. CSCMTs included 3 benign tumors (1 angioma and 2 benign myoepitheliomas) and 67 malignant tumors that after IHC were diagnosed as malignant myoepithelioma (64%), carcinoma and malignant myoepithelioma (19%), hemangiosarcoma (8%), undifferentiated sarcoma (5%), peripheral nerve sheath tumor (3%), and fibrosarcoma (2%). The diagnosis based on the HE-stained section differed from the diagnosis after IHC in 75% of the malignant cases. The majority of malignant CSCMTs were solitary (57%) large tumors (6.42 ± 3.92 cm) with low metastatic potential and high survival rate (8% tumor-related mortality). Higher sarcoma grade was associated with older age (P = .034) and greater tumor size (P = .037). Malignant CSCMTs need to be evaluated by IHC to ensure the histotype and the relatively benign clinical behavior, despite their large size.

Co-occurrence of a metastatic mammary liposarcoma and an ovarian sex-cord stromal tumor in a dog

Sarcoma arising in the mammary gland is a rare tumor in dogs, and primary liposarcoma with metastatic behavior has never been previously reported among canine mammary tumors. A 14-year old female poodle had a mammary mass diagnosed as pleomorphic liposarcoma. Two years following surgical removal, the tumor recurred in the mammary gland with lymph node metastases. In addition, a sex-cord stromal tumor was identified in the ovary. Immunohistochemistry was performed on both tumors that were positive for oestrogen and progesterone receptors. Moreover, the ovarian tumor was positive for calretinin. This is the first report to the authors' knowledge, of the co-occurrence of a pleomorphic liposarcoma of the mammary gland and an ovarian sex-cord stromal (gonadostromal) tumor in the dog.