Objectives: This study aimed to investigate the histological characteristics and treatment efficacy of non-immunoglobulin G4-related fibrosing mediastinitis and discuss differential diagnoses for this rare entity. Methods: We present a case study of non-immunoglobulin G4-related fibrosing mediastinitis diagnosed on core biopsy and treated with steroids. A total of four 18-gauge core needle biopsy specimens were obtained for surgical pathology. Analysis of the patient's medical history, radiological characteristics of fibrosing mediastinitis, histological features, immunohistochemistry results, the differential diagnosis and treatment efficacy of different types of fibrosing mediastinitis was performed. Results: This report describes a unique presentation of fibrosing mediastinitis (syncope and weight loss) that was concerning for malignancy. Histological, laboratory and radiographical studies confirmed the diagnosis of non-immunoglobulin G4-related fibrosing mediastinitis. The patient received corticosteroid treatment which showed marked improvement after 1 month of treatment. Conclusions: Fibrosing mediastinitis is an extremely uncommon entity with unknown pathogenesis, and it is more important to rule out malignancy and infection than to delineate between fibrosing mediastinitis and IgG4-related disease. In doing this, we may reasonably initiate a trial of corticosteroids which may prove beneficial, as in this patient. More studies on the pathogenesis of fibrosing mediastinitis are necessary to guide better directed treatments.

Pathological evaluation of prostate needle biopsies is labor-intensive and often requires ancillary immunohistochemistry (IHC), increasing cost and diagnostic turnaround time (TAT). Artificial intelligence (AI)-based decision-support tools may improve efficiency, but clinical deployment requires institutional validation and assessment of real-world impact. Within a fully digital pathology practice, we performed institutional validation of an AI-assisted prostate biopsy decision-support tool using routine clinical cases, with pathologist-rendered diagnoses as ground truth. Following validation, the tool was implemented into the routine sign-out. A retrospective pre–post analysis compared prostate biopsy cases signed out during 3-month periods before and after implementation, excluding a transition month. Diagnostic TAT was defined as the interval from whole-slide image scan completion to final sign-out. IHC utilization was recorded. Weighted median TATs and IHC use were compared using standard statistical methods. The validation cohort met all predefined acceptance criteria, demonstrating high AI performance (sensitivity 91–100%, specificity 99%, positive-predictive value 98%, negative-predictive value 96%, area under the curve 0.97). Following clinical implementation, diagnostic TAT decreased by 30% and IHC utilization decreased by 38%. Institutional validation and clinical implementation of an AI-assisted prostate biopsy decision-support tool were associated with significant reductions in diagnostic TAT and IHC utilization. When deployed as an adjunct within a digital workflow, AI assistance may enhance efficiency while preserving pathologist responsibility for final diagnosis.

Signet ring cell carcinoma, a type of gastrointestinal system-related cancer, rarely metastasizes to the skeletal muscle. We present signet ring-cell carcinoma in a 28-year-old man who presented with left lower extremity pain and swelling. Imaging showed thickening of the distal esophagus, intestines, and bladder wall. Endoscopy revealed friable gastric mucosa and stenosis in the ascending colon, but biopsies were unrevealing. Leg muscle biopsy showed metastatic adenocarcinoma with focal signet ring features. Carcinoembryonic antigen and cancer antigen 19-9 were elevated. A gastrointestinal primary tumor was suspected. Our case urges clinicians to consider this rare cancer in patients presenting with skeletal muscle mass.