Amyloidosis can involve the gastrointestinal (GI) tract, and deposition can present with varied histologic patterns that make recognition challenging. This retrospective observational study aimed to characterize the deposition patterns in the GI tract and evaluate key quality metrics, including discrepant cases, to improve recognition and provide insight for accurate diagnosis. Sixty-two patients (195 biopsies) with amyloid involvement of the luminal tract were reviewed. Amyloid subtyping by mass spectrophotometry was available for 59 patients. Immunoglobulin light chain (AL) was the most commonly identified subtype (60%), followed by serum amyloid A (AA; 19%) and transthyretin (ATTR; 16%). 150/195 biopsies (77%) were positive for amyloid deposition, with an average of 2.4 positive biopsies per every 3.1 taken per patient. The sites with the highest yield were duodenum (37/37, 100%) and colon (63/74, 85%). Gastric biopsies were most likely to involve the lamina propria (41/45, 91%, P < 0.001), with the background mucosa showing reactive epithelial changes in almost half of the biopsies (20/45, 44%). Several distinct histologic patterns of interstitial deposition were identified, including muscularis mucosae deposition (n = 40, 27% of positive biopsies), peri-Brunner gland (n = 6, 17% of duodenal biopsies), mass-forming (n = 4, 2.7% of positive biopsies, including 3 suspected cases with localized involvement), collagenous colitis-like (n = 3, 4.8% of positive colonic biopsies), and globular (n = 19, 12.7% of positive biopsies). Congo Red was ordered in 81% of cases in which it was requested clinically, with a positivity rate of 30%. Of the 34 cases in which an amyloid workup was requested (but Congo Red was not performed), 14 were positive on reevaluation. Several missed cases had deposition in multiple biopsies, and almost half were missed by subspecialist GI pathologists. Nine misinterpretations were from the stomach, with seven initially diagnosed as chemical or reactive gastropathy. Additional discrepant cases were identified from the duodenum (n = 2) and colon (n = 3), with the vascular-only deposition pattern (n = 3), muscularis mucosae-only deposition (n = 3), and globular pattern (n = 1) identified. Given the challenges of identifying amyloid on hematoxylin and eosin staining, Congo Red ordering percentage should be 100% in clinically suspicious cases unless deposition is definitively seen on hematoxylin and eosin staining.

中文翻译：

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胃肠道淀粉样变性的表征，重点是组织学上不同的间质沉积模式和误解。

淀粉样变性可累及胃肠道，沉积物可呈现出不同的组织学模式，这使得识别具有挑战性。这项回顾性观察研究旨在表征胃肠道中的沉积模式并评估关键质量指标（包括差异病例），以提高识别率并为准确诊断提供见解。对 62 名淀粉样蛋白累及管腔的患者（195 份活检）进行了审查。通过质谱分析可对 59 名患者进行淀粉样蛋白亚型分析。免疫球蛋白轻链 (AL) 是最常见的亚型 (60%)，其次是血清淀粉样蛋白 A (AA；19%) 和运甲状腺素蛋白 (ATTR；16%)。150/195 次活检 (77%) 呈淀粉样蛋白沉积阳性，每位患者每进行 3.1 次活检，平均就有 2.4 次呈阳性活检。产量最高的部位是十二指肠（37/37，100%）和结肠（63/74，85%）。胃活检最有可能涉及固有层（41/45，91％，P <0.001），背景粘膜在几乎一半的活检中显示出反应性上皮变化（20/45，44％）。确定了间质沉积的几种不同的组织学模式，包括粘膜肌层沉积（n = 40，阳性活检的 27%）、布伦纳周围腺（n = 6，十二指肠活检的 17%）、肿块形成（n = 4， 2.7% 的阳性活检，包括 3 例局部受累的疑似病例）、胶原性结肠炎样（n = 3，阳性结肠活检的 4.8%）和球状（n = 19，阳性活检的 12.7%）。临床需要使用刚果红的病例中有 81% 被使用，阳性率为 30%。在 34 例要求进行淀粉样蛋白检查（但未进行刚果红检查）的病例中，14 例重新评估呈阳性。几例漏检病例在多次活检中都有沉积，其中近一半被亚专科胃肠道病理学家漏检。九个误解来自胃部，其中七个最初被诊断为化学性或反应性胃病。从十二指肠 (n = 2) 和结肠 (n = 3) 中发现了其他不一致的病例，其中仅血管沉积模式 (n = 3)、仅粘膜肌层沉积 (n = 3) 和球状模式 (n = 3) = 1) 已识别。鉴于在苏木精和伊红染色上鉴定淀粉样蛋白的挑战，在临床可疑病例中刚果红排序百分比应为 100%，除非在苏木精和伊红染色上明确看到沉积。