Pathological study of neoplasms surgically excised from animals attended the veterinary teaching hospital

Abstract


Introduction
Surgical pathology of tumours in animals is widely described around the world in both farm and pet animals, with more advanced studies in the prevalence of each tumour type and their grading with prognosis (1). In Iraq, few studies are conducted to explain types of tumours in different species of animals, most of them are present to the scientific community as case reports, which emphasizing on describing these cases from a clinical perspective, only a few of them were conducting a pathological study to clear their histopathological architecture of neoplastic cells (2)(3)(4)(5). In Iraq, especially in pet animals, the prevalence of this condition is obscure, and they were recorded as a case report only, without advanced study to causes and pathology of them (6). The most common types of tumour that have been recorded in Iraq are cutaneous papilloma, cutaneous fibroma, hepatic adenoma, cutaneous squamous cell carcinoma, lipoma, and thymoma (2)(3)(4)(5). Few of previous studies explained the histological nature of these types of tumours; others were describing the gross lesions with emphasizing on the clinical aspects of these cases (7). In Mosul city, the neoplastic masses which have been recorded are bovine cutaneous papilloma, cutaneous squamous cell carcinoma, and mixed thymic tumour (2,3,5). This study aimed to investigate the pathology of surgically excised tumours in animals that attended Veterinary Teaching Hospital (VTH), College of Veterinary Medicine, University of Mosul.

Tumour mass collection
The suspected animals with an abnormal mass that attending to the VTH has been sent to the surgical department starting from October 2018 to August 2019. The tissue samples were excised, and different sections of these samples have been taken from different part of the masses. The samples were immersed in 10% neutral buffered formalin for at least 27 hours to be submitted later for histopathological examination (8).

Surgical procedure
Different species of animals prepared under different protocols of anaesthesia or deep sedation using xylazine and/ or ketamine to varying doses according to species of animal ( Table 1). The masses wholly removed and the site of operation was sutured with simple interrupted suture technique in all animals. The collected tissue samples were sent for histopathological examination.

Histopathological protocol
Collected neoplastic samples were previously fixed in buffered 10% formalin. The specimens were grossed carefully at 0.5 cm thickness for tissue processing. Then, the samples were dehydrated in alcohol, cleared by xylol, infiltrated and embedded by host paraffin wax. After that, these tissue samples were sectioned at 6µm thickness and stained with routine Harris' Hematoxylin and alcoholic Eosin (HE), Masson's trichrome stain (MT), and Periodic Schiff's reagent stain (PA) (8).

Results
The total number of neoplastic cases that have been recorded during the study were 36 cases in different species of animals ( Table 2). The prevalence of tumors incidence was in cattle 30.6%, sheep 22.2%, dog 19.4%, poultry 13.9%, cat 11.1, and in goat 2.8% ( Figure 1). Depends on the results explained in table 3, the results showed that sixteen tumour type had been recorded in which either one type or more than one in each neoplastic case. The percentage of these tumours type was SCC 22.22%, fibroma 19.44, adenoma 13.89%, pulmonary adenomatosis and fibrosarcoma 11.11% each, leucosis and lymphoma 8.33% each, thymoma and VTT 2.78% each ( Figure 2).

Squamous cell carcinoma
This type of tumour is recorded in eight cases in skin and vagina, mostly in cattle which characterized by the presence of keratin pearls. This structure is composed of the centric layer of keratin produced by neoplastic keratinocytes which present at the edge of these pearls. Also, it associated with the presence of collagen fibers, especially when a mixed type of fibroma related to squamous cell carcinoma ( Figure 3).

Fibroma and fibrosarcoma
The fibroma is recorded in seven cases of skin while fibrosarcoma recorded in four cases. Fibroma characterized by presence polymorphic fibroblast that either spindled or oval shape presents in dens stroma of abundant collagen fibers. This tumor mass characterized by a few blood vessels supply with a complete absence of necrotic or degenerated tissue ( Figure 4). On other hands, fibrosarcoma composed mainly from neoplastic fibroblast that arranged in a herringbone like patterns which give its diagnostic histological feature that known as cell nests. These neoplastic cells characterized by scant cytoplasm with active mitotic figures of an elongated nucleus. The neoplastic cells associated with moderate mucin deposit in affected tissue ( Figure 5).

Adenoma
Adenoma was recorded in five cases in intestines, mainly this tumour present with heavy deposition of collagen fibers and major blood vessels. The affected epithelial cells lose their typical architectures and appear less cellular and maturation than other epithelial cells. These structures arranged either in the tube or villous or may be presently mixed of both types. The nucleus presents near the basement membrane of affected cells with scant cytoplasm that show at the edge of neoplastic cells ( Figure 6).

Pulmonary adenomatosis
This type of tumor was recorded in four cases of sheep. The tumor cells characterized by hyperplastic proliferation of pneumocytes types II into cuboidal or columnar. This construction composed from collagen deposition with scattered infiltration of macrophages. The nucleus characterized by well-identified mitotic figures and positive reaction to Schiff's regent in the cytoplasm (Figure 7).

Lymphoid leucosis
It is recorded in three cases of domesticated back yard chickens. It characterized by the presence of uniform large neoplastic lymphoblast with the vacuolated nucleus, prominent mitotic figures, and poorly define cytoplasmic membrane. This tumor found in different organs included lung, heart, kidney, and bursa of Fabricius (Figure 8).

Lymphoma
This type of tumor was recorded in three cases. It showed polymorphic infiltration of lymphoblast in the skin, that diffusely present in the extracellular matrix of collagen fibers, with moderately basophilic cytoplasm. The nucleus is round or oval or vacuolated with basophilic nuclei ( Figure  9).

Thymoma
It is recorded in one case of a rooster. This type of tumor is polymorphic lymphocytes that appear as oval or spindle in shape with scant cytoplasm of the ill-defined cytoplasmic membrane ( Figure 10).

Venereal transmissible tumor
This transmissible tumor has been recorded in one case of the cat in vulva and vagina. The neoplastic features composed from large oval to round cells with a pleomorphic nucleus that showed active mitotic figures. The cytoplasm and its membrane are poorly defining and contained vacuoles in affected cells ( Figure 11).

Discussion
In this study, the total number of cases were attended to the VTH from October 2018-August 2019, that was diagnosed with a different type of neoplastic growth was thirty-six cases. The prevalence of these tumors in an other type of animals was in cattle 30.6%, in sheep 22.2%, in dog 19.7%, in poultry 13.9%, in cat 11.1%, and goat 2.8%. It has been confirmed that the most common tumor in Iraq where a cutaneous hemangiosarcoma sheep in Basra city (6). Furthermore, teratoma has been recorded in ovaries of cattle at Thi-Qar city (4).           A case of gingival squamous cell carcinoma has been recorded by accident in ewe where it characterized by the presence of keratin pearls due to hyperplasia of neoplastic keratinocytes (3). A case of vaginal fibrosarcoma was described in a bitch aged ten years. These tumor mass diagnosed based on the presence of specific cell arrangement known as cell nests with hyperchromatic nuclei of welldifferentiated fibroblasts (2).
A case of the mixed thymic tumor was designated in a rooster of a local breed that composed from squamous cell carcinomas due to presence of keratin pearls and welldifferentiated thymoma and lipoma (5).
A case of diffuse lymphoma, leiomyoma, and VTT was diagnosed in vulvar and vaginal in dogs (9). In the current study, the high number of cases have been recorded in cattle. These may be due to dense breeding of bovine species in this area with decrease number of pet animals, the most common type of tumor has been detected as squamous cell carcinoma, this may be related to changes in the environment that initiate, promote and induct these tumors especially in skin of these animals (10).
The most common type of tumor recorded in this study was squamous cell carcinomas, the diagnosis of this type is depended upon the presence of keratin pearls that can be described as hyperplasia of keratinocytes with pleomorphism (11).
A fibroma and fibrosarcoma have been recorded in this study were diagnosed depended upon the presence of bizarre fibrocytes with polymorphism and normochromic nuclei in the dense stroma of whorls collagen fibers (12).
Adenoma was described in many cases, recorded depended upon metaplasia and dysplasia of epithelial cells into cuboidal to columnar with the presence of nucleus near the basement membrane (13).
Ovine pulmonary adenomatosis was recorded in sheep in the current study, the micromorphological appearance of this tumor described as a transformation of pulmonary epithelial cells into columnar cells which either embedded in dense collagen stroma or scant deposition of collagen fibers (14).
Lymphoid leucosis recorded mainly in backyard chickens described as a normal proliferation of large lymphocytes that infiltrated in many organs like muscles, lung, and kidney; these neoplastic lymphocytes are recorded with prominent mitotic figures (15).
Many cases of lymphoma were recorded mainly in the cat, where they described as massive infiltration of lymphocytes or lymphoblast of large size that diffusely invade the whole layers of skin (16).
Thymoma also a popular type of tumor in chickens especially that affect with lymph proliferative viruses as in case of Marek's diseases in chickens, this tumor composed from atypical polymorphic T lymphocytes with ill-defined borders and they characterized by large size with a nucleus in spindle shape (5).
Venereal transmissible tumor was found as a common type of tumor in Hawshar dogs (9). In contrast, in the current study, this tumor was recorded in cats, it is characterized in both species large cells which is either macrophages or monocytes that appears as round, oval or spindle in shape that arranged in cord or sheets with a poor differentiated cytoplasmic membrane that usually contained vacuoles (9).

Conclusion
In conclusion, the incidence of neoplastic tumor between domestic and pet animals is varied, and its types were wieldy diverse from benign to malignant one that can be recurrent or even cause death in affect animals. Also, the result of the current study conducted that the high incidence of animal affected with tumor was cattle, and the tumor type was squamous cell carcinoma.