Finally, p16 has been recently proposed as a diagnostic marker to differentiate atypical polypoid adenomyoma (APA) from myoinvasive endometrioid carcinoma; indeed, p16 often shows diffuse positivity in the fibromyomatous stroma of APA and negativity or focal positivity in the stroma of myoinvasive carcinoma [32,33,34]. This evidence concerns the gene CDKN2A and endometrioid adenocarcinoma.