Comparative Value of Clinical, Cytological, and Histopathological Features in Feline Mammary Gland Tumors; an Experimental Model for the Study of Human Breast Cancer

Background: The diagnosis of breast lesions is usually confirmed by fine-needle aspiration cytology (FNAC) or histological biopsy. Although there is increasing literature regarding the advantages and limitations of both modalities, there is no literature regarding the accuracy of these modalities for diagnosing breast lesions in high-risk patients, who usually have lesions detected by screening. Moreover, few studies have been published regarding the cytopathology of mammary tumors in cats despite widespread use of the animal model for breast cancer formation and inhibition. The objective of the present study was to evaluate the diagnostic interest of cytological and histopathological analysis in feline mammary tumours (FMTs), in order to evaluate its possible value as an animal model.

Methods: The study was performed in 3 female cats submitted to surgical resections of mammary tumours. The mammary tumours were excised by simple mastectomy or regional mastectomy, with or without the superficial inguinal lymph nodes. Female cats were of different breeds (1 siamese and 2 persians). Before surgical excision of the tumour, FNA cytology was performed using a 0.4 mm diameter needle attached to a 8 ml syringe held in a standard metal syringe holder. The cytological sample was smeared onto a glass slide and either air-dried for May-Grünwald-stain and masses were surgically removed, the tumours were grossly examined and tissue samples were fixed in 10%-buffered-formalin and embedded in paraffin. Sections 4 μm thick were obtained from each sample and H&E stained.

Results: Cytologically, atypical epithelial cells coupled to giant nucleus, chromatin anomalies, mitotic figures, spindle shape cells, anisocytosis with anisokaryosis and hyperchromasia were found. Histologically, these tumors are characterized by pleomorphic and polygonal cell population together with mitotic figures, necrotic foci and various numbers inflammatory foci. Also, spindle shaped cells, haemorrhage localized in the different regions, local invasiveness and enlarged nuclei were observed. The samples included 3 tumors of mammary glands mammary tumors were complex carcinomas (n = 2) and adenocarcinoma (n = 1). The histological grades of the 3 cases were as follows: grade II, (1/3); grade III, (2/3) with high mitotic index. The preferential localization of mammary neoplasms was in the inguinal lobe (1/3 case) and abdominal lobes (2/3 cases). Furthermore, 1case of the inguinal mass affected the left caudo-inguinal lobe and 2cases right cranio and caudo abdominal lobes.

Conclusion: The study concluded that cytology could be used as a quick, rapid, field diagnostic technique in combination with histopathology for the diagnosis of feline mammary tumors (FMTs). Our findings in feline MTs indicate that FMTs could be useful as an animal model of human breast cancer. Moreover, because of the similarity of the cytohistopathological findings in the human and feline mammary gland tumours, it is possible to use the same cytopathological criteria applied in human pathology for the diagnosis of feline mammary gland tumours.

Virtual Slide: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/2047361423103295.