How would you tell the difference between a fibroid big cell tumor (benign) and a lipoma?

I had injured the palm of my hand and several weeks later a mass began to form under the skin. It kept growing and I recently had it removed. It was 4 cm in diameter. My review of the literature makes me think this was a lipoma. The MD said the lab referred to it as a fibroid, big cell tumor. I had injured my thumb on a previous occasion and my body's response was the growth of a tumor there as well, about 1-1.5 cm in diameter. It's still there, never had it removed.

A tumour always have blood vessels in it, that does not happens with a lipoma. When the tumour is removed it is analysed by a pathologist, he/she analyses the types of cells and blood vessels it has and in that way it is possible to know the kind of tumour it is. Some studies that can be done to see the tumour characteristics are ultrasound, Tomography and magnetic Resonance. It depends of the body area affected and the symptoms of the patient. It is necessary to be seen by a doctor ( a surgeon ) he/she is the appropriate person to order the tests and eventually remove the tumour.

The tissue has to be examined under a microscope to determine the type.