Aggressive Angiomyxoma, Angiomyofibroblastoma, and Cellular Angiofibroma of the Lower Female Genital Tract: Related Entities With Different Outcomes.

Introduction Mesenchymal tumors of the lower female genital tract (FGT) are a miscellaneous group of tumors that include aggressive angiomyxoma (AAM), angiomyofibroblastoma (AMFB), cellular angiofibroma (CAF), and related entities. Histologically, these tumors are composed of stromal cells admixed with vessels, with some minor histological differences. An accurate diagnosis of these tumors is important owing to the differences in the outcome. In this study, we determined the clinicopathological characteristics of these tumors in our population and their association with recurrence.  Methods This was a retrospective cross-sectional study conducted at the Department of Histopathology, Aga Khan University, from January 2005 to December 2019 over a period of 15 years. A total of 207 cases that were diagnosed as AAM, AMF, and CAF were selected for inclusion in the study. Clinical data, including age and location of the lesion, were obtained from histopathology referral forms. Tissue blocks of all cases were retrieved. Follow-up data were obtained from the patient files, and information regarding disease recurrence was recorded. One histological section from each tissue block was stained with hematoxylin and eosin stain, and histopathological findings were recorded. Additionally, immunohistochemical (IHC) studies, including vimentin, smooth muscle actin (SMA), and desmin were conducted on representative tissue blocks. Final histopathological diagnoses were rendered considering clinical, histopathological, and IHC findings. Results The median age of patients involved in the study was 33 years and the median tumor size was 5 cm with a predilection for the vulva (47.3%). AAM showed a predilection for patients between the ages of 31-45 years, while AMFBs and CAFs were most common in younger age groups of less than 30 years. In 46.8% of cases, the tumor size of AAM was between 6 and 10 cm, while in all cases of CAF (100%) and the majority of AMFB cases (53.2%) the tumor size was smaller than 5 cm. Histologically, in all cases of AAM, the lesional cells were spindle (100%), whereas, in 13% of cases epitheloid cells were observed, with myxoid stroma in 92.2% cases. The presence of stromal smooth muscle was noted in 42.9% of cases, in 79.2% of cases the vessels were thick-walled, with 54.5% having hyalinized vessels, and most of the cases (77.9%) had ill-defined borders. Among IHC findings, AMFB was most frequently positive for actin (62.2%), while AAM and AMFB showed more frequent staining for desmin compared to CAF. A significantly higher recurrence rate was observed in AAM (27.3%), compared to AMFB and CAF. A significant association of recurrence was seen with tumor size. It was noted that the recurrence rate was directly proportional to the size of the tumor and was highest (60%) with a tumor size of more than 10 cm. Conclusion In our study, we noted that AMFB was the most common among the three mesenchymal tumors of the lower FGT. In contrast, AAM had the highest recurrence rate, and recurrence was significantly associated with tumor size. Histological findings, especially the type of stromal cells and background vasculature, are of utmost importance for the correct recognition of these tumors, while the role of IHC studies is limited.