Swelling is a common term with a general meaning. Swelilng indicates that n organ (or part of it) is enlarged. In their basic root meanings, the terms “swelling” and “tumor” are synonyms. Both indicate an organ or body part enlargement.
Talsohe term “swelling ” is used as a synonym for the Latin term “edema”. “Edema” means increased quantity of liquid in the space between cells (interstitial space). Edema causes enlargement (swelling) of the whole body, some body parts, organs or part of an organ. Edema is present in two main conditions: during inflammation and circulatory stasis. Inflammations are caused by infections or injuries. During injuries, inflammation AND possible hemorrhages in a closed space (haematoma) can cause swelling. Circulatory stasis can be either local (venous thrombosis) or general (heart failure).
The term “tumor” is usually used (incorrectly) as a synonym for the Latin term “neoplasm”. Neoplasm indicates newly created tissue that originates from previously normal cells that have lost their control of proper division and function. Such cells divide themselves and increase their number without control that lead to organ enlargement (swelling) in some types of neoplasm. In tumors, enlargement is caused by an increase of the number of tissue cells and not interstitial liquid. Tumor is an incorrect synonym for neoplasm because in many cases there is no enlargement of the organ, but rather, destruction of the cells, tissue, and organ (malignant neoplasm). Some types of neoplasm such as leukemia cannot be officially called "tumors", for example.
In many cases it is physically impossible to note a difference between swelling and a tumor (neoplasm). If the swelling is caused by inflammation there are accompanying symptoms of pain, redness, warmness and disturbed function. Tumors, however, are not usually followed by these additional symptoms. Benign tumors are always manifested with some kind of tissue enlargement. Malignant tumors of the penis are usually manifested with ulceration.
The first diagnostic procedure for penis tumor or swelling is physical examination that includes inspection and palpation. That’s why I recommend you to visit your GP and if necessary he will send you to an urologist.