Pilomatrixoma is a relatively common lump which appears under the skin classically on the face, neck or arms in children. It is often described as starting quite small, sometimes even thought to be a mosquito bite, but then slowly enlarges over time. It is 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. It is curative and simple excision is the treatment of choice.