Objectives To describe the rare presentation, imaging and histological findings, and treatments in patients with IgG4‐related disease (IgG4‐RD) and diagnostic pitfalls and difficulties. Methods Cases of sinonasal IgG4‐RD were retrieved, and clinicopathological features were reviewed. Results Seven cases of sinonasal IgG4‐RD were identified over an 11‐year period, including four males and three females, with an age range of 19–66 years (median 58 years). Patients presented with symptoms related to the mass effect of the lesions or the destructive nature of the disease including fullness, swelling, obstruction, and pain. Serum IgG and IgG4 levels, IgG/IgG4 ratios, storiform fibrosis, obliterative phlebitis, and plasma cell infiltration were seen in varying proportions. Bony erosion and tissue inflammation were present in some cases. Conclusion Sinonasal IgG4‐RD is exceedingly rare among other IgG4‐RD and varied in its clinical presentation thus posing as a clinically difficult disease to diagnosis. Proper clinical, pathological, and immunohistopathological analysis is required for accurate diagnosis. Such disease should be considered in all cases of similar presentation to those in this study. Level of Evidence: 4.

ObjectivesApproximating the maxillary sinus natural ostium's (MSNO) natural position during anterograde surgery is challenging, as only a single visual “landmark,” the maxillary line, is routinely offered to guide the identification of the MSNO in three‐dimensional space. Despite almost 40 years of endoscopic sinus surgery (ESS) experience in North America, maxillary recirculation and discontinuity between the natural and surgical ostia are commonly encountered during revision ESS. Consequently, we feel an additional visual landmark would assist in localizing the MSNO with or without image guidance. In this study, we aim to provide a second reliable landmark in the sinonasal cavity.MethodsWe present a cadaveric anatomical landmark series that provides a second visual landmark for the MSNO, which we have labeled the transverse turbinate line (TTL): a 2‐millimeter zone of confidence for the craniocaudal positioning of the MSNO that can be combined with the anteroposterior (AP) landmark of the maxillary line.ResultsIn our study, 40 cadaveric sinuses were dissected, and the TTL was found to correspond consistently with the zone between the superior and inferior aspects of the MSNO.ConclusionWe anticipate that this second relational landmark may decrease the time required for anterograde access to the MSNO in trainees, increase the accuracy of identification, and translate to lower long‐term recirculation and maxillary surgery failure rates.Level of EvidenceN/A Laryngoscope, 2023

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