Identification of Patterns of Morphological Organization of Visual Organs at the Development of Malignant Neoplasms in Cats

1. Introduction

Eye diseases are quite common in animals and humans. For example, in Russia, 20–45% of people over 40 have eye diseases [1]. Neoplasms of the eye and its appendages are rare in the general etiology of neoplasms [2]. The tumor process has a comprehensive effect on the body, more pronounced in malignant neoplasms consisting of moderately or poorly differentiated cells [3]. In both humans and mammals, “paraneoplastic” syndromes are clinical and laboratory manifestations of the tumor process caused by the release of a large number of biologically active substances by tumor cells, such as cytokines, interleukins, hormone-like peptides, growth factors, and antigens [4]. They present with hematological, endocrine, dermatological, neurological disorders, gastrointestinal changes, cancer-associated ophthalmopathy [4,5,6,7,8,9]. To date, the collection of cytological samples from or near the human eye is underused. Ocular cytology is relatively simple to perform and its use is informative in making a diagnosis [10,11,12,13]. Great variability in the cytological characteristics of the visual organs of animals affected by ophthalmological diseases has been found [14]. The most common indications for ocular cytology include: scrapings or cleaning of the conjunctiva and cornea to determine the type and etiology of conjunctivitis and keratitis; aspirates of aqueous fluid or vitreous body if septic uveitis or “endophthalmitis” is suspected; and aspiration of solid tissue or cystic masses on the surface of, in, or around the eyeball [15]. Pathological examination of the eyes when making a diagnosis during organ-preserving or liquidating surgical intervention is carried out quite rarely [16]. Since modeling malignant neoplasms is a complex task, cytological-morphological study of the development of existing malignant neoplasms in animals can make it possible to clarify the causes of the occurrence and pathogenesis of the tumor process, and to develop effective methods for its prevention and treatment.

The aim of the work: to study the “morphological-functional indices” (MFIs) of organs and systems in animals in terms of the development of malignant neoplasms based on the “histological-pathological” analysis of the eyeballs after bilateral and unilateral enucleating.

2. Materials and Methods

The study of MFIs of organs and systems in animals in terms of malignant neoplasm development was performed based on “histological-pathological” analysis of the eyeballs after bilateral and unilateral enucleating in the 19 cats living in Moscow and admitted to a veterinary clinics for diagnostic and therapeutic manipulations. Data on the animal species, breed, presence and manifestation of concomitant oncological diseases were collected.

During enucleating of the eyeball and accessory organs, premedication was performed: meloxicam 0.2 mg/kg, maropitant 1 mg/kg, cefazolin 30 mg/kg. Then induction was performed using tiletamine and zolazepam 3 mg/kg, propofol 3-5 mg/kg and ET intubation. Anesthesia was maintained with isoflurane 0.5-1 vol.%. Histological studies of enucleated eyes were performed in the control and experimental groups, which were represented in approximately equal proportions by animals with and without a history of oncological diseases, males 52.6% (control - 37.5% and experiment - 62.5%) and females 47.4% (control - 66.7% and experiment - 33.30%). The study sample included the following cat breeds: crossbreeds - 15 (78.95%) cases, Bengal - 3 (15.79%) cases and Sphynx - 1 (5.26%). Morphological studies were carried out on animals of the age category mainly 7-12 years - 79.0% (control - 31.6% and experiment - 47.4%) and over 13 years old - 21.0% (control - 5.2% and experiment - 15.8%). After enucleating, the eyeballs were immediately placed in labeled sealed containers containing 10% neutral buffered formalin. Subsequently, after fixation, pathological material was excised, during which a macroscopic examination of the eyeballs was performed. In this case, for each animal, one or two sections of each eyeball (right and left) were obtained, for a total of 2-4 sections. After histological processing, the tissues were embedded in paraffin, microtomy was performed to obtain sections 5 μm thick. Preparation and staining of histological preparations with hematoxylin and eosin were carried out according to the standard technique. After preparation, histological preparations of the eyeballs, kidneys and oral cavity were subjected to “histological-pathological” examination. Examination of the preparations was carried out on an Olympus CX23 microscope (objective x10; eyepieces x4, x10, x40). An assessment was made of changes in the following structures of the eyeball: cornea, choroid, retina, optic nerve region, and lens.

3. Results

It was found that gastrointestinal “paraneoplastic” syndromes were the most common in the studied sample of animals. The manifestation of this syndrome was noted in 90.59% of cats. These symptoms worsened in 98.16% of cases with the use of chemotherapy and / or radiation therapy. This was confirmed by the results of endoscopic studies (Figure 1).

In the digestive system, the mucous and submucous layers of all organs are affected with the formation of acute inflammation with hemorrhages. It was found that ophthalmological paraneoplastic syndromes were the most common in the studied sample of animals (Figure 1 and Figure 2).

Since the sample included a large proportion of neoplasms of unknown morphology, additional histopathological studies of autopsy material from organs were carried out: lung tissue, kidney and jaw (Figure 3).

Histological studies were used to supplement and expand the diagnoses in animals. When examining the lung tissue of an 11-year-old female Bengal cat diagnosed with lymphoma, the following diagnosis was made: diffuse venous-capillary congestion, mild chronic-active interstitial pneumonia with parenchymal fibrosis (Figure 4).

Autopsy material from a male mixed-breed cat was used to examine a neoplasm of the oral cavity. “Histological-pathological” examination revealed squamous cell carcinoma (Figure 5).

In about 94.7% of cats, histologically significant deviations in the structure of the cornea were not found (Figure 6).

All cats had no histological findings in the choroid (Figure 7).

In 100.0% of cases, histological examination of the retina of cats revealed that the vessels were not dilated, without significant histological changes (Figure 8).

The optic nerve of cats was examined in 63.2%, inflammatory infiltrate was not present (Figure 9).

In the structure of the cornea, a single specimen of deformation of the corneal wall (artifact) and slight thickening due to hyperplasia of the anterior corneal epithelium were revealed (Figure 10).

In the first case, a female Bengal cat, 11 years old, with a history of lymphoma, had a neoplasm of the iris, melanocytoma (Figure 11).

In the second case, a female Bengal cat, 11 years old, with a history of neoplasm of the eyeball, was diagnosed with melanoma (Figure 12).

In the third case, a mixed-breed cat, 9 years 2 months old, history of neoplasm of the eye, diffuse neoplasm of the iris, melanoma was established (Figure 13).

In the fourth case, a mixed-breed cat with a history of an intestinal neoplasm has a diffuse formation of the iris. The sections show a neoplasm of lymphoid tissue, large cell lymphoma (Figure 14).

In the first case, during a histological examination of the eyeball of a mixed-breed male cat, with a history of chest neoplasm, iris cysts were noted (Figure 15).

In the second case, during a histological examination of the eyeball of a mixed-breed female cat, 7 years old, with a history of a neoplasm of the mammary gland, cysts of the iris were also noted, however, they were less pronounced than in the previous patient (Figure 16).