Infantile haemangiomas are common, benign vascular tumours. Other vascular lesions, which can mimic infantile haemangiomas, include myofibroma, vascular malformations, rhabdomyosarcoma or dermatofibrosarcoma protuberans. The diagnosis of a haemangioma can usually be made based on clinical presentation and medical examination. This is a case report describing a four-week-old male with a red, cutaneous lesion lateral to the left eye. The lesion was noticed a week after birth and was rapidly growing. It was diagnosed as an infantile haemangioma and propranolol was started at the age of four weeks. The tumour did not show any response to propranolol after three weeks of treatment, and continued to grow. After four weeks of therapy, the tumour ulcerated and started to bleed. The patient was admitted and transfused because of anaemia. Intralesional corticosteroids were administered in order to try to stimulate involution. The tumour started to regress but the diagnosis of an infantile haemangioma was questioned and an excision biopsy was performed. Histopathology confirmed the lesion as a myofibroma. In the literature, more than 2500 children have been treated with propranolol. The authors describe unpublished data from their centre (n=31), which showed that a first response to propranolol was noticed within two to three weeks. The authors report that no serious side-effects of propranolol occurred in any of their patients. This paper contributes to the literature on propranolol, which can be a helpful diagnostic tool to distinguish an infantile haemangioma from other tumours. In conclusion, when a young child presents with what appears to be a typical haemangioma and propranolol does not result in a decrease of the size of the vascular tumour within a month, a biopsy of the tumour should be considered in order to rule out malignancy.