This study confirms the high incidence of WWTR1-CAMTA1 and YAP1-TFE3 rearrangements in EHE and indicates that the staining pattern for TFE3 IHC is critical for specificity.

BACKGROUND: Digital pathology practice is rapidly gaining popularity among practicing anatomic pathologists. Acceptance is higher among the newer generation of pathologists who are willing to adapt to this new diagnostic method due to the advantages offered by whole slide imaging (WSI) compared to traditional light microscopy (TLM). We performed this validation study because we plan to implement the WSI system for diagnostic services. OBJECTIVES: Determine the feasibility of using digital pathology for diagnostic services by assessing the equivalency of WSI and TLM. DESIGN: A laboratory-based cross-sectional study. SETTING: Central laboratory at a tertiary health care center. MATERIALS AND METHODS: Four practicing surgical pathologists participated in this study. Each pathologist blindly reviewed 60 surgical neuropathology cases with a minimum 8-week washout-period between the two diagnostic modalities (WSI vs. TLM). Intraobserver concordance rates between WSI and TLM diagnoses as compared to the original diagnosis were calculated. MAIN OUTCOME MEASURES: Overall intraobserver concordance rates between each diagnostic method (WSI and TLM) and original diagnosis. SAMPLE SIZE: 60 in-house surgical neuropathology cases. RESULTS: The overall intraobserver concordance rate between TLM and original diagnosis was 86.3% (range 76.7%-91.7%) versus 80.8% for WSI (range 68.3%-88.3%). These findings are suggestive of the superiority of TLM, but the Fleiss' Kappa statistic indicated that the two methods are equivalent, despite the low level of the K value. CONCLUSION: WSI is not inferior to the light microscopy and is feasible for primary diagnosis in surgical neuropathology. However, to ensure the best results, only formally trained neuropathologists should handle the digital neuropathology service. LIMITATIONS: Only one diagnostic slide per case rather than the whole set of slides, sample size was relatively small, and there was an insufficient number of participating neuropathologists. CONFLICT OF INTEREST: None.

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Appendiceal diverticular disease is a rare entity. We report a case of appendiceal diverticulitis mimicking acute appendicitis and diagnosed postoperatively on histopathology. A 28-year-old female presented with a 2-day history of shifting periumbilical pain associated with nausea and anorexia. A computed tomography scan of the abdomen demonstrated acute appendicitis. She was taken to laparoscopic appendectomy. Histopathology showed appendiceal diverticulitis, and perforation of an inflamed diverticulum with periappendicitis. Diverticulosis of the appendix is classified as congenital and acquired. Diagnosis can be made preoperatively by imaging. In this case, diverticulosis was not radiologically evident, and was interpreted as acute appendicitis. Gross appearance of the resected appendix was not suggestive of diverticulitis. Other cases reported that the gross specimen had evidence of diverticular disease. Surgeons should be aware that inflamed appendixes may harbor different pathologies warranting further management.