Targeted RNA sequencing in the routine clinical detection of fusion genes in salivary gland tumors.

Salivary gland tumors represent a diverse group of neoplasms that occasionally pose a diagnostic challenge for pathologists, particularly with limited sampling. Gene fusions, which may reflect genetic drivers, are increasingly recognized in a subset of these neoplasms, and can be leveraged for diagnostic purposes. We performed a retrospective analysis on a cohort of 80 benign and malignant salivary gland tumors, enriched for subtypes known to harbor recurrent fusion events, to validate the diagnostic use of a targeted RNA sequencing assay to detect fusion transcripts. Testing identified fusion genes in 71% (24/34) of pleomorphic adenoma and carcinoma-ex-pleomorphic adenoma, with 56% of cases showing rearrangement of PLAG1 and 15% HMGA2. In addition to confirming known partners for these genes, novel PLAG1 fusion partners were identified, including DSTN, NTF3, and MEG3; CNOT2 was identified as a novel fusion partner for HMGA2. In adenoid cystic carcinoma, 95% of cases (19/20) were positive for a fusion event. MYB was rearranged in 60% (12/20), MYBL1 in 30% (6/20), and NFIB in 5% (1/20); two tumors exhibited novel fusion products, including NFIB-TBPL1 and MYBL1-VCPIP1. Fusion genes were identified in 64% (9/14) of cases of mucoepidermoid carcinoma; MAML2 was confirmed to partner with either CRTC1 (43%) or CRTC3 (21%). One salivary duct carcinoma was found to harbor a novel RAPGEF6-ACSL6 fusion gene. Finally, as anticipated, gene fusions were not detected in any of the five acinic cell carcinomas included in the cohort. In summary, targeted RNA sequencing represents a diagnostically useful ancillary technique for identifying a variety of existing, and novel, fusion transcripts in the classification of salivary gland neoplasms.

Can peer feedback substitute for faculty feedback in predoctoral dental education?

PURPOSE/OBJECTIVES: The ability to give and receive feedback is a key skill to develop during predoctoral dental education, and the use of peer feedback specifically offers distinct benefits including a different understanding of material due to peers' proximity of knowledge development and assisting with overburdened instructors. However, it is unclear if peer feedback offers similar quality to instructor feedback. METHODS: Dental students in two different graduation years provided quantitative and qualitative peer feedback on a case-based oral and maxillofacial pathology simulation. The data from these exercises were aggregated and analyzed to compare the quality of qualitative feedback to course examination scores. Student perceptions of peer feedback were also recorded. RESULTS: The mean quality of feedback was not correlated with course examination scores, though the number of times students gave high-quality feedback and received high-quality feedback was correlated with course examination scores. Student feedback overall had a lower quality than instructor feedback, though there was no significant difference between instructor feedback quality and the maximum student feedback quality received. Student perceptions of the utility of feedback were positive. CONCLUSION: While instructor feedback is more reliable and consistent, our findings suggest that in most instances, at least one peer in moderate-sized groups is able to approximate the quality of instructor feedback on case-based assignments.

Intraoperative Use of Wide-Field Optical Coherence Tomography to Evaluate Tissue Microstructure in the Oral Cavity and Oropharynx.

Importance: Involvement of deep margins represents a significant challenge in the treatment of oropharyngeal cancer, and given practical limitations of frozen-section analysis, a need exists for real-time, nondestructive intraoperative margin analysis. Wide-field optical coherence tomography (WF-OCT) has been evaluated as a tool for high-resolution adjunct specimen imaging in breast surgery, but its clinical application in head and neck surgery has not been explored. Objective: To evaluate the utility of WF-OCT for visualizing microstructures at margins of excised oral and oropharyngeal tissue. Design, Setting, and Participants: This nonrandomized, investigator-initiated qualitative study evaluated the feasibility of the Perimeter Medical Imaging AI Otis WF-OCT device at a single academic center. Included participants were adults undergoing primary ablative surgery of the oral cavity or oropharynx for squamous cell carcinoma in 2018 and 2019. Data were analyzed in October 2019. Exposures: Patients were treated according to standard surgical care. Freshly resected specimens were imaged with high-resolution WF-OCT prior to routine pathology. Interdisciplinary interpretation was performed to interpret WF-OCT images and compare them with corresponding digitized pathology slides. No clinical decisions were made based on WF-OCT image data. Main Outcomes and Measures: Visual comparisons were performed between WF-OCT images and hematoxylin and eosin slides. Results: A total of 69 specimens were collected and scanned from 53 patients (mean [SD] age, 59.4 [15.2] years; 35 [72.9%] men among 48 patients with demographic data) undergoing oral cavity or oropharynx surgery for squamous cell carcinoma, including 42 tonsillar tissue, 17 base of the tongue, 4 buccal tissue, 3 mandibular, and 3 other specimens. There were 41 malignant specimens (59.4%) and 28 benign specimens (40.6%). In visual comparisons of WF-OCT images and hematoxylin and eosin slides, visual differentiation among mucosa, submucosa, muscle, dysplastic, and benign tissue was possible in real time using WF-OCT images. Microarchitectural features observed in WF-OCT images could be matched with corresponding features within the permanent histology with fidelity. Conclusions and Relevance: This qualitative study found that WF-OCT imaging was feasible for visualizing tissue microarchitecture at the surface of resected tissues and was not associated with changes in specimen integrity or surgical and pathology workflow. These findings suggest that formal clinical studies investigating use of WF-OCT for intraoperative analysis of deep margins in head and neck surgery may be warranted.

SS18 Break-Apart Fluorescence In Situ Hybridization is a Practical and Effective Method for Diagnosing Microsecretory Adenocarcinoma of Salivary Glands.

Molecular analysis has allowed for refinement of salivary gland tumor classification and, in some cases, the recognition of entirely new tumor types. Microsecretory adenocarcinoma (MSA) is a salivary gland tumor described in 2019 characterized by microcystic growth, bland cytomorphology, luminal secretions, fibromyxoid stroma, and S100/p63 positivity with negative p40. Most important, MSA is defined by MEF2C-SS18 fusion. While this fusion has, to this point, been detected by next-generation sequencing, this is a technique that is currently inaccessible in most diagnostic laboratories. On the other hand, SS18 break-apart fluorescence in situ hybridization (FISH) is widely available and frequently used as an adjunct for diagnosing synovial sarcoma. It is not known if SS18 break-apart FISH is positive in tumors with MEF2C-SS18, or if it is entirely specific for MSA. Break apart FISH for SS18 was performed on 4 cases of MSA, as well as 8 tissue microarrays (TMAs) containing 423 various salivary gland carcinomas: 26 acinic cell carcinomas, 35 adenocarcinomas not otherwise specified, 96 adenoid cystic carcinomas, 3 basal cell adenocarcinomas, 20 epithelial-myoepithelial carcinomas, 15 hyalinizing clear cell carcinomas, 3 intraductal carcinomas, 12 myoepithelial carcinomas, 117 mucoepidermoid carcinomas, 30 polymorphous adenocarcinomas, 45 salivary duct carcinomas, 19 secretory carcinomas, and 2 undifferentiated carcinomas. SS18 break-apart FISH was also performed on whole slides of 2 tumors from the TMAs. All MSA cases demonstrated classic split patterns on SS18 break-apart FISH. On the TMAs, 374 cases were evaluable by FISH, and 372 cases were clearly negative for SS18 rearrangement. Two cases, both mucoepidermoid carcinomas, had rare split signals below the positivity threshold of 12% on their TMA cores, so FISH was performed on whole sections. On the whole sections both tumors were unequivocally negative for SS18 rearrangement. Taken together, SS18 break-apart FISH was 100% sensitive and 100% specific for a diagnosis of MSA. SS18 break-apart FISH, a diagnostic tool widely available in pathology laboratories, appears to be a highly accurate method for diagnosing MSA of salivary glands. Accordingly, this new tumor type may be molecularly confirmed without needing to resort to highly specialized techniques like next-generation sequencing.