SMARCA4 gene encodes BRG1 , a member of the SWItch/sucrose non-fermentable protein family involved in epigenetic transcriptional regulation of important cellular processes. In the uterine corpus, SMARCA4 / BRG1 deficiency is associated with a novel class of undifferentiated uterine sarcomas, characterized by younger age onset, rhabdoid histology, focal phyllodiform architecture, high-risk pathologic findings, and dismal prognosis. Herein, we report a case of a 34-year-old Asian woman with a SMARCA4 / BRG1 -deficient uterine tumor fulfilling the clinicopathologic features of an undifferentiated uterine sarcoma. However, the tumor exhibited several unique features that have not been previously emphasized, including (1) conspicuous phyllodiform architecture recapitulating conventional adenosarcoma, (2) rhabdoid tumor cells forming cords and keratin-positive cohesive epithelial islands, and (3) cooccurrence with a spatially distinct and discrete endometrial complex atypical hyperplasia from the rest of the proliferation. By immunohistochemistry, the tumor cells were diffusely positive for synaptophysin, whereas BRG1 was lost. Pertinent molecular findings included frameshift mutations in the SMARCA4 gene, mutations in histone modification and chromatin remodeling genes, including KMT2C , ARID1B , KAT6A , and NCOR1 , and mutations in Wnt signaling involving APC and CTNNB1 . Copy number gain in MDM2 and CDK4 were also identified. The tumor mutation burden was intermediate (6.8/MB) and it was microsatellite stable. On balance, our case exhibited morphologic and molecular features that overlap with (1) an undifferentiated uterine sarcoma, (2) an adenosarcoma with sarcomatous overgrowth, and (3) a mixed adenosarcoma and undifferentiated endometrial carcinoma. These hybrid features further expand the molecular-morphologic spectrum of SMARCA4 / BRG1 -deficient uterine neoplasms.

In recent years, there has been a surge of interest in clinical digital pathology (DP). Hardware and software platforms have matured and become more affordable, and advances in artificial intelligence promise to transform the practice of pathology. At our institution, we are launching a stepwise process of DP adoption which will eventually encompass our entire workflow. Out of necessity, we began by establishing a whole slide imaging (WSI)-based frozen section service. We proceeded in a systematic manner by first assembling a team of key stakeholders. We carefully evaluated the various options for digitizing frozen sections before deciding that a WSI-based solution made the most sense for us. We used a formalized evaluation system to quantify performance metrics that were relevant to us. After deciding on a WSI-based system, we likewise carefully considered the various whole slide scanners and digital slide management systems available before making decisions. During formal evaluation by pathologists, the WSI-based system outperformed competing platforms. Although implementation was relatively complex, we have been happy with the results and have noticed significant improvements in our frozen section turnaround time. Our users have been happy with the slide management system, which we plan on utilizing in future DP efforts. There are various options for digitizing frozen section slides. Although WSI-based systems are more complex and expensive than some alternatives, they perform well and may make sense for institutions with a pre-existing or planned larger DP infrastructure.