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Diseases |
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Indian Rhino |
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Malignant tumours are found in both domesticated and wild animals. The incidence of cancer is reported to be less in wild animals, probably because of their short lifespan, but zoo animals with increased longeviy are known to suffer from cancer. The epidemiological study of cancer in zoo animals provides a good basis of understanding the environmental and biological factors responsible for carcinogenesis.
A case if squamous cell carcinoma of the skin in an old Indian rhinoceros ( Rhinoceros unicornis ) maintained at the Municipal Zoological Gardens, Bombay, is reported here.
A male rhinoceros was brought to Bombay Zoo in 19**. When the animal was about 50 years old and weighed about 3000 kg an ulcer developed on the skin over the nose adjoining the horn. The ulcer extended all round the horn until the horn fell off. The growth then invaded deeply into the skinduring a period of 14 to 16 months and did not respond to treatment. Upon examination, veterinary and medical toxicologists uspected that the lesion was malignant. The animal was tranquilised and a biopsy was taken for histopathological studies. Because the lesion was wide and inoperable, it was dressed with an ointment containing an anti-cancer drug, but there was no noticeable improvement.
The wound had a cauliflower-like appearance with an undulating surface and a thickened border. The animal gradually lost weight, became emaciated and died about two-and-a half years after the first appearance of the ulcer. The post mortem examination was carried out 18 hours after death but no other metastases were evident.
The biopsy tissue was processed and slides were prepared and stained with haematoxylin and exosin. The section revealed well differentiated areas of squamous cell carcinoma with keratinisation in the centre which stained brightly with eosin. There were columns of squamous cells invading the dermis and subcutis. The tumour cells were polymorphic with centrally situated large vesicular nuclei some of which showed mitotic divisions. The proliferation of squamous cells to stratification and keratin formation were clear indications of their attempt to differentiate. From the epidermis the growth invade dthrough the dermis and subcutis as far as the nasal bone which was shown at post mortem examination to have been eroded.
Carcinomas of the skin are known to take a long time to metastasise, like bovine ocular squamous cell carcinoma which vary from non-invasive to malignant as observed by Russell and others. Similarly the horncore cancer, a squamous cell carcinoma in Indian zebu takes a long time metastasise.
The Indian rhinoceros has a single horn made up of filamentous tubules of keratin which aee secreted by the skin and cemented together to form a hard projection. This projection is fixed to the skin and does not have a bone support like the horn of ruminants. The ulcer on the skin adjacent to the base of the horn may have developed owing to the constant trauma and irritation caused by the horn striking against hard onjects. The ulcer then became a squamous cell carcinoma which invaded around and beneath the horn until the horn separated and exposed a broad wound.
Over most of its body the Indian rhinoceros has a very thick skin arranged in characteristic massive folds, but on the nose the skin is thin. Cancer of the thick skin is probablu very rare.
This is thought to be the first report of a squamous cel carcinoma of the skin of the rhinoceros.
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Squamous cell carcinoma in an Indian rhinoceros
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