CNS tumor diagnosis in dogs often relies on immunohistochemistry (IHC) given similar histologic features among tumors. Most CNS tissue samples encountered by diagnostic pathologists are collected during autopsy, and postmortem specimens can be susceptible to autolysis and prolonged formalin fixation, both of which have the potential to influence IHC results and interpretation. Here we evaluated the effects of experimentally controlled autolysis induced by delayed tissue fixation (sections of brain held for 2, 4, 8, 12, 24, 48, and 72 h in 0.9% NaCl at either room temperature or 37°C prior to fixation) as well as the effects of prolonged formalin fixation times (1 wk, 1 mo, 2 mo) on a panel of 8 IHC markers (CNPase, GFAP, Iba1, OLIG2, PGP9.5, MAP2, NeuN, synaptophysin) relevant to brain tumor diagnosis. Prolonged fixation of up to 2 mo had no detrimental effect on any immunomarker except NeuN, which had reduced immunolabeling intensity. Delayed fixation led to autolytic changes as expected, on a gradient of severity corresponding to increased time in saline prior to fixation. Several immunomarkers should be used with caution (CNPase, OLIG2) or avoided entirely (MAP2, NeuN) in markedly autolyzed brain and brain tumor tissues. Our results suggest that autolysis has minimal effect on most immunomarkers, but that advanced autolysis may cause a loss of specificity for GFAP, MAP2, and PGP9.5, a loss of intensity of CNPase and OLIG2, and loss of labeling with MAP2 and NeuN. Prolonged fixation affected only NeuN, with mildly decreased intensity.

中文翻译：

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自溶和长期福尔马林固定对正常犬脑组织组织形态学和免疫组织化学的影响：实验研究

鉴于肿瘤之间相似的组织学特征，狗的中枢神经系统肿瘤诊断通常依赖于免疫组织化学 (IHC)。诊断病理学家遇到的大多数中枢神经系统组织样本都是在尸检过程中收集的，尸检标本可能容易发生自溶和长时间福尔马林固定，这两者都有可能影响 IHC 结果和解释。在这里，我们评估了延迟组织固定诱导的实验控制自溶的影响（固定前将脑切片在室温或 37°C 下在 0.9% NaCl 中保存 2、4、8、12、24、48 和 72 小时） ）以及延长福尔马林固定时间（1 周、1 个月、2 个月）对与大脑相关的 8 个 IHC 标记物（CNPase、GFAP、Iba1、OLIG2、PGP9.5、MAP2、NeuN、突触素）的影响肿瘤诊断。长达 2 个月的长时间固定对除 NeuN 以外的任何免疫标记物都没有有害影响，NeuN 会降低免疫标记强度。延迟固定导致了预期的自溶变化，其严重程度梯度对应于固定前盐水中时间的增加。在明显自溶的脑和脑肿瘤组织中，应谨慎使用几种免疫标记物（CNPase、OLIG2）或完全避免使用（MAP2、NeuN）。我们的结果表明，自溶对大多数免疫标记物的影响很小，但高级自溶可能会导致 GFAP、MAP2 和 PGP9.5 特异性丧失、CNPase 和 OLIG2 强度损失以及 MAP2 和 NeuN 标记损失。长时间固定仅影响 NeuN，强度略有下降。