Introduction

In Veterinary Medicine, the first article with cytological examinations dating from 80's (Guedes et al. 2000). In Human Medicine, cytopathology has been employed since the 19th century, and started in 1867 with studies of cells from ascitic liquid of patients with ovarian tumors. A part from that, in 1917 Papanicolaou began researches on exfoliative cells cytology, and established in 1928 the diagnosis for human uterine cancer out of vaginal secretions (Magalhães et al. 2001). The main advantages of cytological examination is the speed of diagnosis, its simplicity, low cost, and generally not be invasive, requiring no sedation or local anesthesia for the procedure. The complications of cytology are hemorrhages, infections, injury of adjacent tissue and dissemination of malignant cells, all of which are considered rare events (Guedes et al. 2000). Studies comparing cytological and histopathological diagnosis showed average efficiency of 83.3% to 85.3% of the cytological diagnosis, with a concordance, respectively, in 75 of 90 cases, and in 128 of 150 cases (Guedes et al. 2000, Magalhães et al. 2001). Considering only the round-cells tumors, the effectiveness increases to 95%, helping the definitive diagnosis of these tumors because they have characteristics better defined in cytological examinations then in histopathology (Guedes et al. 2000), presenting histological models frequently similar (Lavalle et al. 2003). One of the aims of the cytological examination refers to the classification of injuries, assisting on the diagnosis, prognosis and treatment of the diseases. In general, the changes observed in cytological examinations can fit in the following categories: normal or hyperplastic tissue, cystic formation, inflammation or cellular infiltrate, response to tissue injury, cancer or nondiagnostic sample; this last category composed by samples from insufficient cellular material or excessive contamination of blood, not allowing diagnostic interpretation (Raskin & Meyer 2003). Among the cancers, a study with 150 dogs of both genders and of different races, found that 74 (49.3%) were mesenchymal, 26 (17.3%) epithelial, seven (4.7%) of neuroectodermal origin, seven (4.7%) of sexual cord and interstitium, 16 (10.7%) were transmissible venereal tumors, and 20 (13.3%) were cancers of mammary glands (Magalhães et al. 2001). In another study, 64 dogs with cutaneous round-cell tumors were put up for cytological examination, where were found 25 mast-cell tumors, 15 histiocytomas, nine lymphomas and 15 transmissible venereal tumors (Duncan & Prasse 1979). The mast cell tumors was also the highest incident tumor in another study involving cutaneous tumors (Griffith set al. 1984). On cytology of mammary gland, a study with 35 bitches suffering from breast tumors verified on cytological examination the presence of 37% of carcinomas, 28.6% of malignant mixed tumors, and 20% of benign tumors, including one adenoma, one chondroma, three benign mixed tumors and two mastitis; and the addition of 12.5% with inconclusive cytological diagnoses (Zuccari et al. 2001). This study aimed to describe the main variations found in the cytological examination of numerous injuries in dogs and cats attended by the cytology diagnostic service of the Hospital of Veterinary Medicine Professor Firmino Marsico Filho, at the Fluminense Federal University, categorizing them according to species, gender and diagnoses obtained.

Materials and Methods

To achieve this study, 650 cytological examinations reports were reviewed from July 2002 to December 2008. We used 612 dogs and 38 cats presenting varied age, sex and race. The slides used in this study were fixed at normal room temperature, and stained by the Romanowsky method (Giemsa). Were found from the 650 cases a total of 754 cytological diagnoses, since in many animals were collected materials from different injuries that usually resulted in different diagnoses. The variations found were recorded in a spreadsheet of the program Microsoft Excel®, and then grouped up into categories according to criteria described in the literature (Raskin & Meyer 2003), which are: normal or hyperplasic tissue, cystic formation, inflammation, response to tissue injury, tumors and nondiagnostic sample. The results within each category were analyzed according to species, sex and diagnoses found.

Results

A total of 754 cytological diagnoses were evaluated, in which 34 (4.5%) were classified in the category of normal tissue / hyperplasia, 59 (7.8%) as cystic formation, 195 (25.9%) as inflammation, four (0.5%) as response to tissue injury, 346 (45.9%) as cancer and 116 (15.4%) as a non-diagnostic sample. The analysis of this result showed that inflammation and cancer were the main cytological categories found, followed by non-diagnostic sample, cystic formation, normal tissue / hyperplasia and response to tissue injury. Besides the high incidence of these alterations, the results revealed the wide use of cytological examination by veterinary practitioner as an attempt to differ inflammatory from neoplastic processes. From the total of samples, the canine species was the one with highest occurrence compared to the feline species, with, respectively, 716 (95%) and 38 (5%) animals. This predominance of the dogs was also verified in the analysis of the alterations classified by category. Concerning genders, females (64%) showed a slight predominance on the alterations detected when compared to males (36%). In the normal tissue / hyperplasia category the most frequent diagnosis was reactive lymph nodes, comprising 67.6% of the alterations, followed by squamous cells hyperplasia (17.6%) and tissue samples that were completely unchanged (14.7%), which refers to 0.7% of total samples, including all categories. The cytological diagnosis of hyperplasia or normal tissue comprised 53% of males and 47% of females, and 88% of the animals from canine species. In the category cystic formation the cyst epidermoid was the most frequent diagnosis (64.4%) followed by breast cyst (17%), cystic formation from undetermined origin (11.9%) and other cysts of lower frequency (6.8%). The cytological diagnosis of cystic formation comprised 37.3% of males and 62.7% of females, and 93.2% of the animals from canine species, and 6.8% from feline species. Neutrophilic inflammatory process was the most frequent diagnosis (68.2%) in the inflammation category, followed by mixed inflammatory process (11.8%), pyogranulomatous (7.2%) and eosinophilic (4%). In this category, infection caused by Malassezia sp. represented 8.7% of the total of samples. The cytological diagnosis of inflammation comprised 39.5% of males and 60.5% of females, and 92.3% of the animals from canine species, and 7.7% from feline species. Fibroplasia reaction (100%) was the only diagnosis obtained for the category of response to tissue injury, and 100% of animals were males and 75% of animals were canines, the other 25% were felines. Of the total of diagnoses obtained in the cancer category, transmissible venereal tumor (15.6%) was the most frequent diagnosis followed by sarcoma from undetermined origin (11.5%), lipoma (10.1%), malignant mixed tumor (9.2%), lymphoma (9.2%), mammary gland carcinoma (9.2%), mast-cells tumor (8.4%), perianal gland adenoma (4.6%), basal cells tumor (3.7%), fibrosarcoma (2.6%) and others cancers of lower frequency (15.3%), including adenocarcinoma of perianal gland, sebaceous adenoma and adenocarcinoma, squamous cells carcinoma, transitional cells carcinoma, epulides, fibroma, hemangiopericytoma, hemangiosarcoma, melanoma, osteosarcoma, papilloma, Sertoli cell tumor. The diagnoses in this category comprised 32.6% of males and 67.3% females, and 96.2% dogs and 3.7% cats.

Discussion and Conclusions

Within the cancer category the tumors of epithelial origin were the highest incidence (36%), followed by round-cell tumors (35.2%) and mesenchymal (28.5%). Neuroendocrine tumors were not observed during the evaluated period. The results of this study were different from those described by other authors (Magalhães et al. 2001) that described a higher incidence of mesenchymal tumors. Among the round-cells tumors, studies cited earlier (Duncan & Prasse 1979) showed a predominance of mast cell tumors in 39.1% of the samples, followed by histiocytoma with 23.4% and transmissible venereal tumor with 23.4%, and then lymphoma in 14,1% of cases. This study had a higher incidence of transmissible venereal tumor comprising 42.8% of the total of round cells tumors, followed by lymphoma with 25.4%, mast cells tumors with 23%, round-cells tumors of unknown origin with 3.2% and histiocytoma with 2.4% of cases. This difference can be attributed to increased use of this extension service by people from underprivileged social classes, since this tumor is related to known promiscuous behavior by dogs. In the category of non-diagnostic samples 33.6% were males and 66.4% were females, 99.1% were canine species and 0.9% were feline species. This category included samples with insufficient amount of material for cytological analysis and samples excessively contaminated with blood. The results presented in this study highlights the importance of diagnostic cytology in veterinary medicine, not only by the numerous advantages related to the speed in obtaining the diagnosis and the simplicity of technique, but also by the large number of diagnoses that are possible to be obtained.

References

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