If a soft tissue enlargement appears to be a tumor, the clinician must next determine if the enlargement is benign or malignant. Benign tumors are typically better defined or circumscribed and have a slower growth rate, measured in months and years, than malignant neoplasms. Malignant neoplasms are more likely to be painful and cause ulceration of the overlying epithelium than benign lesions. Since malignant neoplasms invade or infiltrate surrounding muscle, nerve, blood vessels, and connective tissue, they are fixed or adherent to surrounding structures during palpation. Some benign tumors are also fixed to surrounding structures, but other benign tumors are surrounded by a fibrous connective tissue capsule, which may allow the lesion to be moved within the tissue independent of surrounding structures.
Benign tumors can be subdivided into four categories: epithelial, mesenchymal, and salivary gland tumors, and cysts of soft tissue. Although soft tissue cysts are not tumors, their historical and clinical features resemble those of benign tumors.