Which of the following is mismatched?

a. oncology: diagnosis and treatment of tumors
b. carcinoma: characteristic cell types found in benign tumors
c. mutation: changes in DNA involving substitutions, deletions, insertions, recombinations, and translocations
d. leukemia: cancer of the immune system affecting circulating cells
e. malignant transformation: gain of ability to form a cancer

A carcinoma is a cancer that occurs in the cells that lines the internal organs and the skin. This carcinoma is like other cancerous cell which can spread to other organs of the body and cause cancer in them which is the characteristic of malignant tumor.

Benign tumors do not have the ability to cause cancer because benign tumor does not spread to other organs. They remain at their position and do not cause more harm to the body like a malignant tumor. Therefore carcinoma is not a characteristic cell types found in benign tumors.