A specimen retrieval instrument comprises a handle assembly, an actuating rod, an introducer tube, and a retrieval bag. In some versions the specimen retrieval instrument further comprises a modular cartridge containing the retrieval bag. Upon translation of the actuating rod within the tube, the cartridge opens, releasing and opening the retrieval bag for receiving a specimen. A center spindle may be included where the spindle includes a slot for inserting a portion of the retrieval bag and wrapping the retrieval bag about the spindle. Some versions of the specimen retrieval instrument further comprise a rotating cam actuator that opens and closes a pair of support arms attached to the retrieval bag. Some versions of the specimen retrieval instrument further comprise rotating curved support arms operable to open and close the retrieval bag. Pins registered to helical grooves may provide rotation of the support arms as the support arms translate.