Context.— Tissue contaminants on histology slides represent a serious risk of diagnostic error. Despite their pervasive presence, published peer-reviewed criteria defining contaminants are lacking. The absence of a standardized diagnostic workup algorithm for contaminants contributes to variation in management, including investigation and reporting by pathologists. Objective.— To study the frequency and type of tissue contaminants on microscopic slides using standardized criteria. Using these data, we propose a taxonomy and algorithm for pathologists on “floater” management, including identification, workup, and reporting, with an eye on patient safety. Design.— A retrospective study arm of 1574 histologic glass slides as well as a prospective study arm of 50 slide contamination events was performed. Using these data we propose a structured classification taxonomy and guidelines for the workup and resolution of tissue contamination events. Results.— In the retrospective arm of the study, we identified reasonably sized benign tissue contaminants on 52 of 1574 slides (3.3%). We found size to be an important parameter for evaluation, among other visual features including location on the slide, folding, ink, and tissue of origin. The prospective arm of the study suggested that overall, pathologists tend to use similar features when determining management of potentially actionable contaminants. We also report successfully used case-based ancillary testing strategies, including fluorescence in situ hybridization analysis of chromosomes and DNA fingerprinting. Conclusions.— Tissue contamination events are underreported and represent a patient safety risk. Use of a reproducible classification taxonomy and a standardized algorithm for contaminant workup, management, and reporting may aid pathologists in understanding and reducing risk.

Primary adrenal angiosarcomas are exceedingly rare with a rapidly progressive clinical course and a poor outcome. Establishing the diagnosis can be challenging, and it is complicated by the fact that there are no characteristic clinical or imaging features that are pathognomonic for angiosarcoma. Histologically, they can overlap with other more commonly encountered adrenal tumors. Herein, we present an otherwise healthy 41-year-old woman diagnosed with a primary adrenal epithelioid angiosarcoma. We aim to expand the knowledge of the sparse literature existing on primary adrenal angiosarcomas to help better understand the diagnostic features, clinical behavior, and management of these rare tumors.

Interval appendicitis shows histological differences from acute appendicitis and may mimic Crohn disease and other forms of granulomatous appendicitis Aims: While patients presenting with clinical signs and symptoms of acute appendicitis (AA) often receive surgical intervention shortly after presentation, certain patients may instead receive nonoperative management initially, with appendectomy later. The histology of such interval appendicitis (IA) has only been described in small series. Also, we have noticed a recent increase in the incidence of IA specimens at our institution. Methods and results: We identified appendectomy specimens in our department during 2018 with available haematoxylin and eosin slides and electronic clinical data, and evaluated multiple histological findings. Cases were then divided into AA and IA, based on clinical history (AA if the patient presented to the hospital within 1 week of symptom onset and underwent appendectomy within 48 h; IA if appendectomy was delayed at least 1 week). Changes between groups were compared. The cohort included 165 cases (125 AA, 40 IA). Findings significantly more common in AA included mucosal acute inflammation, mural acute inflammation and acute serositis. Findings significantly more common in IA included Crohn-like mural inflammation, mural fibrosis, goblet cell hyperplasia, granulomas, xanthogranulomatous inflammation, haemosiderinladen macrophages and granulation tissue. The rate of IA in 2018 (24%) was noticeably higher than in previous years. Conclusion: Acute inflammatory changes are more common in AA but can remain present in IA. Mural fibrosis, serosal adhesions, haemosiderin-laden macrophages and granulation tissue suggest IA. Granulomas and xanthogranulomatous inflammation can also be seen in IA, and Crohn-like mural inflammation is not uncommon. These histological patterns can guide signout and prevent diagnostic errors, particularly when clinical information is unavailable.