Mule spinners' cancer or mule-spinners' cancer was a cancer, an epithelioma of the scrotum. It was first reported in 1887 in a cotton mule spinner. In 1926, a British Home Office committee strongly favoured the view that this form of cancer was caused by the prolonged action of mineral oils on the skin of the scrotum, and of these oils, shale oil was deemed to be the most carcinogenic. From 1911 to 1938, there were 500 deaths amongst cotton mule-spinners from cancer of the scrotum, but only three amongst wool mule spinners.