Craniofacial osteosarcoma is rare (2-10% of all osteosarcomas). Most low grade fibroblastic osteosarcomas of the long bones are characterized by amplification of chromosome12q including MDM2 and CDK4 genes. This study aims to investigate the utility of MDM2 and CDK4 immunostains as well as MDM2 FISH in craniofacial osteosarcomas as a means of distinguishing them from benign fibro-osseous lesions. Cases of primary osteosarcoma and benign fibro-osseous lesions of the craniofacial bones were identified in the diagnostic pathology archives. MDM2 (SMP14 and/or IF2) and CDK4 (D9G3E and/or DCS-31) immunostains were performed on a representative block from each osteosarcoma and benign case. Fluorescence in situ hybridization (FISH) for MDM2 was performed on non-decalcified osteosarcomas. In osteosarcomas, the rate of expression of either MDM2 IF2, MDM2 SMP14, CDK4 DCS-31, or CDK4 D9G3E was 72.7% (8/11 cases), usually focal and weak. Using the MDM2 IF2 clone and the CDK4 DCS-31 clone, MDM2 and CDK4 were negative in lesional cells in all 14 benign fibro-osseous lesions. Using the IF2 and SMP14 clones, MDM2 nuclear expression was present in associated osteoclast-like giant cells in both benign and malignant cases. Of 4 successful cases, 1 high grade osteosarcoma was positive for MDM2 amplification. MDM2 or CDK4 expression or MDM2 amplification may aid in a diagnosis of head and neck osteosarcoma. However, when absent, sarcoma is not excluded. Due to focal weak expression of MDM2 in tumor cells in conjunction with nuclear expression in associated giant cells, caution should be exercised when interpreting positive stains.

Context. Pathology practices have begun integrating digital pathology tools into their routine workflow. During 2020 the coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged as a pandemic causing a global health crisis that significantly affected the world population in several areas, including medical practice, and pathology was no exception. Objective. To summarize our experience in implementing digital pathology for remote primary diagnosis, education and research during this pandemic. Design. We surveyed our pathologists (all subspecialized) and trainees to gather information about their use of digital pathology tools before and during the pandemic. Quality assurance and slide distribution data were also examined. Results. During the pandemic, the widespread usage of digital tools in our institution allowed a smooth transition of most clinical and academic activities into remote with no major disruptions. The number of pathologists using whole slide imaging (WSI) for primary diagnosis increased from 20 (62.5%) to 29 (90.6%) out of a total 32 (100 %) pathologists, excluding renal pathology and hematopathology, during the pandemic. Furthermore, the number of pathologists exclusively using WSI for primary diagnosis also increased from 2 (6.3%) to 5 (15.6%) during the pandemic from the total of 32 (100%) pathologists. From 35 (100%) survey responses from attending pathologists, 21 (65.6%) reported using WSI for remote primary diagnosis following the Centers for Medicare and Medicaid Services waiver. Of these 21 pathologists, 18 (87%) responded that if allowed, they will continue using WSI for remote primary diagnosis after the pandemic. Conclusions. The pandemic served as a catalyst to pathologists adopting a digital workflow into their daily practice and realizing the logistic and technical advantages of such tools.

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