Pilomatrixoma is a relatively common lump which appears under the skin classically on the face, neck or arms in children. Its history is that it is often described as starting as something quite small and sometimes even thought to be a mosquito bite but then slowly enlarges over time. It is actually a benign tumour of the hair follicle.Their natural history is that they continue to grow slowly. They may have a yellow or whitish appearance underneath the skin and can feel quite hard and craggy. Simple excision is the treatment of choice and is curative.