Final answer:
The term describing specimen removal in one piece is excision.
Step-by-step explanation:
The term describing specimen removal in one piece is excision. Excision refers to the surgical removal of a tissue specimen for analysis.
An example of excision is the removal of a mole or a tumor for biopsy. Other options listed in the question, such as biopsy, autopsy, and dissection, do involve specimen removal, but they do not specifically refer to removing the specimen in one piece.