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OBJECTIVE: Endovascular approaches have evolved from a technique practiced at very few centers to a widely available option in the management of arteriovenous malformations (AVMs) of the central nervous system. Embolization can be employed as definitive therapy or as an adjunct to surgical excision. A wide variety of embolic agents have been successfully developed and used in the clinical setting. In addition to facilitating vascular occlusion, embolic agents induce a number of reactive and destructive changes in vessel walls and the surrounding tissue. However, studies examining the pathological changes induced by different embolic agents and varying times of exposure are scarce. The goal of the present study was to compare embolic agents and time of exposure on the pathology in excised specimens. METHODS: The records of the Department of Pathology at the London Health Sciences Centre were searched for embolized AVMs for the 35-year period 1980-2015. All cases were reevaluated for clinical and technical variables and standardized histopathological findings. Cases were grouped by embolic agent, volume of agent used, and time to excision. RESULTS: A total of 101 specimens were identified. Embolic agents were invariably associated with a range of pathological findings, some of which may affect the integrity of vessel walls or the reestablishment of flow, thrombosis, acute and chronic inflammatory changes, angionecrosis, extravasation, and recanalization. The type of embolic agent did not predict differences in the incidence or severity of histopathological changes. Larger volumes of embolic agent were associated with a greater proportion of vessels containing embolic material. AVMs excised early (< 1 week postembolization) contained more acute vasculitis, while those excised later (≥ 1 week postembolization) were more likely to exhibit recanalization and foreign body giant cell infiltrates. CONCLUSIONS: Embolic agents induce a predictable range and temporal progression of pathological changes in cerebral AVMs. The embolic agents studied are indistinguishable in terms of the range and frequency of pathological reactions induced. Greater volumes of embolic agent are associated with more abundant agent within the lesion, but the proportion of vessels and vascular cross-sectional areas containing agent is small. Several changes are significantly associated with time postembolization. Acute vasculitis is a more common finding in the 1st week, while recanalization and foreign body-type granulomatous inflammation are more common at 1 week and beyond.
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BACKGROUND: Total mesorectal excision is the standard of care for patients with rectal cancer. Pathological evaluation of the quality of the total mesorectal excision specimen is an important prognostic factor that correlates with local recurrence, but is potentially subjective. OBJECTIVE: This study aimed to determine the degree of variation in grading, both between assessors and between fresh and formalin-fixed specimens. DESIGN: Raters included surgeons, pathologists, pathology residents, pathologists' assistants, and pathologists' assistant trainees. Specimens were assessed by up to 6 raters in the fresh state and by 2 raters postfixation. Four parameters were evaluated: mesorectal bulk, surface regularity, defects, and coning. Interrater agreement was measured using ordinal α-values. SETTING: The study was conducted at a single academic center. MAIN OUTCOME MEASURES: The primary outcome was agreement between individuals when grading total mesorectal excision specimens. RESULTS: A total of 37 total mesorectal excision specimens were assessed. Reliability between all raters for fresh specimens for mesorectal bulk, surface regularity, defects, coning, and overall grade were 0.85, 0.85, 0.92, 0.84, and 0.91. When compared with all raters, pathologists and residents had higher agreement and pathologists and surgeons had lower agreement. Ordinal α-values comparing pathologist and pathologist's assistant agreement for overall grade were similar pre- and postfixation (0.78 vs 0.80), but agreement for assessing defects decreased postfixation. Among pathologists' assistants, agreement was higher when grading specimens postfixation than when grading fresh specimens. LIMITATIONS: Assessment bias may have occurred because of the greater number of pathologists' assistants participating than the number of residents and pathologists. CONCLUSIONS: The results indicate good interrater agreement for the assessment of overall grade, with defects showing the best interrater agreement in fresh specimens. Although total mesorectal excision specimens may be consistently graded postfixation, the assessment of defects postfixation may be less reliable. This study highlights the need for additional knowledge-transfer activities to ensure consistency and accurate grading of total mesorectal excision specimens. See Video Abstract at http://links.lww.com/DCR/A497.