Tumor Etymology 

The term tumour/tumor is derived from the Latin word for 'swelling' -- tumor. It is similar to the Old French tumour . In the Commonwealth the spelling 'tumour' is commonly used, whereas in the U.S. it is usually spelled 'tumor'.

In its medical sense it has traditionally meant an abnormal swelling of the flesh. The Roman medical encyclopedist Celsus described the 4 cardinal signs of acute inflammation as tumor, dolor, calor, & rubor . His treatise, De Medicina, was the first medical book printed in 1478 following the invention of the printing press.

In contemporary English, the word tumor is often used as a synonym for a cystic growth or solid neoplasm , with other forms of swelling often referred to merely as swellings.

Related terms are common in the medical literature, where the nouns tumefaction & tumescence , are current medical terms for non-neoplastic swelling. This type of swelling is most often caused by inflammation caused by trauma, infection, etc.

Tumors might be caused by conditions other than an overgrowth of neoplastic cells, however. Cysts are also referred to as tumors, even though they have no neoplastic cells. This is standard in medical billing terminology .