Advances in the Diagnosis of Atypical Polypoid Adenomyoma Combining Immunohistochemical and Molecular-Based Approaches: Case Report and Review of the Literature.

Atypical polypoid adenomyoma (APA) is a benign uterine lesion with a premalignant potential and occurs in women of reproductive age. The histological pattern is characterized by irregular epithelial proliferation and muscular stroma. Based on a case report, we performed a systematic review of the literature to assess the main immunohistochemical and molecular markers that contribute to its differential diagnosis against endometrial adenocarcinoma (EC). The distinction is essential for offering to patients a conservative treatment compared to the radical management required for endometrial cancer, a critical issue for the significant physical and psychological consequences that one procedure or another can have on women's health. We performed a meta-analysis of the immunohistochemical markers used for the histological diagnosis of APA, comparing it with our case study. The evaluated markers were beta-catenin, h-caldesmon, desmin, vimentin, smooth muscle alpha-actin, CD10, Ki67, estrogen receptor (ER), progesterone receptor (PR), pan-cytokeratin, PTEN, PMS2, MSH2, MSH6, p53, MLH1, and p16. Discrepancies were observed in the expression of CD10, h- caldesmon, and p16 when comparing APA with EC. The results of the case evaluated by our team showed beta-catenin nuclear expression and positive immunostaining for pan-cytokeratin, ER, and PR in the glands; smooth muscle actin and desmin positive expression in stromal muscle; and p16 positive immunostaining in squamous morules. Moreover, the c.94G>T p. (Asp132Tyr) mutation in the CTNNB1 gene was detected. This study supports the combination of appropriate immunohistochemical and molecular markers, along with the presumptive histological diagnosis, and determines the correct classification of the lesion as APA and not as other malignant pathologies, allowing for the establishment of a treatment protocol adjusted to the biological reality of this pathology.