In this report we describe the case of a young woman with familial adenomatous polyposis who developed metastatic rectal cancer during pregnancy. At diagnosis, we decided to perform a transabdominal laparoscopic adrenalectomy, because of the high risk of bowel obstruction, and to define the origin of the adrenal gland lesion, suspected to be primary on the basis of imaging results. The histological specimen showed a collision tumor between an adrenal metastasis of a rectal tumor and a primary adrenal gland carcinosarcoma. The peculiarity of the case is due not only to its clinical presentation during pregnancy, but also to the presence of this uncommon adrenal collision tumor. A particular challenge for the clinician is to define the priority between these two tumors: the presence of two distinct and colliding aggressive neoplasms poses a problem in the choice of the best therapeutic approach, also given the impossibility to biopsy all metastatic sites. However, we decided to treat the patient as having a metastatic rectal cancer, because we had a solid histological confirmation of metastases.