This paper assesses two cases characterised by an asymptomatic mass of the thigh, triggered by a minor trauma - and primarily diagnosed as a muscle strain and haematoma. After several months with symptoms, both cases developed fulminating symptoms with high temperature, anaemia and increased infection parameters. Both were diagnosed - not uncommonly delayed - with sarcoma of the extremity. Consider sarcoma in cases of long duration with increasing pain which is not related to the size of the trauma, connection to deep fascia, size > 5 cm, rapid or invasive growth, fixation, and solid tumour consistency.