Incidence of basal cell tumours are common in dogs and cats than any other domestic animal species and constitutes 5-10% of all the tumors seen in dogs with higher incidence in male dogs of 1-7 yrs age. In the present study, 14 surgically excised masses from different parts of the dogs were received to the Department of Veterinary Pathology, C.V.Sc, Tirupati for histopathological examination. Of them, four masses revealed characteristic features of different variants of basal cell carcinomas. Grossly, grayish white solitary ulcerated nodules were noticed. On histopathological examination, different variants of basal cell carcinomas were identified as solid, cystic and adenoid patterns.
Basal cell and appendage tumors are very important group of skin tumors in dogs and cats and rare in other domestic animals. Basal cell carcinomas in dogs accounts for 5-10% of total number of tumors and are believed to be originating from uncommitted basal reserve cells of epidermis and adnexa, and exhibits minimal differentiation towards hair follicle or other adnexa (Diters and Walsh 1984). Basal cell tumors are considered as benign and so metastasis is extremely rare. They are very common in male dogs of 1-7 years of age and found commonly in the skin of head, neck, and forelimbs. These tumors generally appear as firm, solitary, dome-shaped elevated masses, which are often ulcerated (Meuten 2002 and Rohit et al., 2014). The size of the tumors ranges from 0.5 to 10.0 cm in diameter. These tumors can break the skin, cause the death of skin tissue, and drains fluid or pus. Cut surface of the tumors are usually grayish white to dark in color. Histopathological appearances of basal cell tumors in dogs have six major patterns namely solid, garland (ribbon), sinusoid, adenoid, cystic and baso-squamous types. The solid and baso-squamous variants are believed to be more aggressive (Nielsen and Cole 1960). The characteristic cells of basal cell carcinomas have prominent oval nuclei with relatively little cytoplasm. The basal cells of basal cell carcinomas differ from basal cells of the epidermis in lacking “intercellular bridges”. Often the cell boundaries are poorly defined. Surgical removal is the effective treatment and reduces the risk of secondary infection and inflammation.
Materials and Methods
Surgically excised tumor masses were submitted to the Department of Veterinary Pathology, C.V. Sc, Tirupati for histopathological diagnosis during the period from January 2015 to December 2015. Detailed history of the cases was collected and examination was carried out and gross changes of tumor masses were recorded. Impression smears were taken from the cut surface of the masses and stained with Giemsa stain. Representative tissue pieces were collected in 10% neutral buffered formalin and processed in 6 µ paraffin embedded sections and stained with haemotoxylin and eosin (H&E) method.
Results and Discussion
Out of 14 surgically excised masses from the dogs, four revealed the features of basal cell carcinoma. The present study was aimed to explain the features of different patterns of basal cell carcinomas in male dogs. The affected dogs were in the age group of 4-6 years and it was in accordance with the studies of Gupta and Tiwary (2009). The tumor growths were raised in the regions of neck and shoulders. The four excised growths have similar gross characteristics of grayish white colour with ulcerated nodules measuring 1-2cm in length. Cytological impressions revealed large cluster of round cells having hyperchromatic nucleus with little cytoplasm (Fig.1).
Fig1: Impression smear showing large cluster of cells with hyperchromatic nucleus with little cytoplasm
On histopathological examination, sections of tumour masses from four dogs revealed solid pattern in two Pomeranians where as cystic and adenoid patterns in each of two German shepherds were also recorded. Of the two cases with solid basal cell carcinomas, one revealed poorly differentiated proliferating basal cells of variable sizes and shapes and the other case showed well differentiated cellular masses (Fig. 2).
The nuclei of the peripheral layer of cellular masses were in palisade with long axes of nuclei perpendicular to the surrounding connective tissue, whereas the other nuclei were arranged in a haphazard fashion. Cystic basal cell carcinomas differ from the solid one by the presence of cystic spaces in the centers of the sheets of neoplastic basal cells (Fig.3).
Cells were arranged in finger like projections with one to two rows of palisading cells in adenoid type of basal cell carcinoma (Meuten 2002) (Fig.4). In all the cases, the nuclei were oval with finely clumped heterochromatin and had one to two prominent mitotic nucleoli. Cellular boundaries were poorly defined (Rohit et al., 2014).
In one case, few inflammatory cells were scattered in the stroma. Based on cytology and histopathology, the present cases were confirmed as different variants of basal cell carcinomas of dogs.