Which of the following can be classified as a benign tumor?

Adenomas are classified as benign tumors because they consist of well-differentiated cells that grow slowly and do not invade surrounding tissues or metastasize to distant sites in the body. Benign tumors typically remain localized and, while they may cause problems based on their size or location, they are not cancerous and do not pose the same level of risk as malignant tumors.

In contrast, carcinoma refers to malignant tumors arising from epithelial cells, indicating a potential for invasion and metastasis. Sarcomas are another type of malignant tumor that originates in connective tissues, such as bones or muscles, and are also associated with aggressive behaviors. Lymphoma, which primarily affects the lymphatic system, is malignant and can lead to the spread of cancer throughout the body. Thus, adenomas stand out as non-cancerous growths, making them the correct answer in this context.