Cutaneous tumours account for about 15% of all neoplasms in the guinea pig. The most common skin tumour is trichofolliculoma, a benign condition of basal cells. Trichofolliculoma most commonly occurs on the dorsum and flanks and can develop to a considerable size; it presents as a firm, roundish subcutaneous nodule. Surgical excision of the lesion is curative. Other types of benign and malignant cutaneous tumours that have been reported are sebaceous adenoma, fibroma, fibrosarcoma, fibrolipoma, undifferentiated sarcoma and adenocarcinoma. Histological examination is necessary after excision of the tumour in order to determine its type.