Which term describes a mass of histologically NORMAL tissue located in an abnormal site?

Correct answer: A. Choristoma

• A. Correct. A CHORISTOMA is normal tissue in an abnormal LOCATION — for example pancreatic tissue growing in the liver, or the classic oral example, an osseous/cartilaginous choristoma of the tongue. It is sometimes called an 'ectopic rest.'
• B. A hamartoma is a disorganized overgrowth of tissue NATIVE to that site (e.g., a hemangioma) — right place, wrong architecture.
• C. A neoplasm is autonomous, unregulated new growth — a choristoma is developmental and non-neoplastic.
• D. A teratoma is a true neoplasm containing tissues derived from more than one germ layer, typically in gonads or midline sites.

Note: Memory hook: choristoma = right tissue, WRONG PLACE. Hamartoma = right place, WRONG AMOUNT/ARRANGEMENT.