Hare with a connective tissue tumour on its head
In early March 2024, a hare (Lepus europaeus) was found in the village Callantsoog, province of North-Holland, with a large growth on its head. The hare was dying. A few months earlier, another dead hare had been found at the same location, but that animal showed no external abnormalities. The dead hare with the tumour was collected for examination at the DWHC.
The hare was a thin, adult male. He had a 6 cm, outward-growing, crater-shaped mass on the bridge of their nose (see photo). The tumour was not attached to the underlying bone tissue.
Microscopic examination showed that this was a tumour: a so-called dermatofibrosarcoma. This is a malignant tumour (“cancer”) of the connective tissue cells in the skin. The cause of this tumour is unknown. Sometimes, fibrosarcoma in hares and rabbits are caused by infection with a myxoma or papilloma virus, but there was no evidence of such an infection in this hare.
