Inverted (Schneiderian) sinonasal papilloma (ISP) is a neoplasm derived from mucosa of the sinonasal tract characterized by local aggressive growth, a tendency to recur and an association with sinonasal carcinoma. The etiology of ISP remains unclear. Recently, identical mutations in exons 19 and 20 of the oncogene EGFR were reported in ISP and ISP-associated sinonasal carcinoma. Nevertheless, it remains unclear whether recurring ISPs show identical EGFR mutations at different time points or whether these mutations are identical throughout the respective ISP sample. We used Sanger sequencing to test 60 formalin-fixed paraffin embedded ISP samples from 40 patients regarding mutations in exons 19 and 20 of EGFR—together with exon 15 of BRAF. Overall, 32 samples of 22 patients showed a mutation in EGFR exon 20, whereas 28 samples of 18 patients showed none. No mutation in EGFR exon 19 was found in any sample. Four samples of four patients showed a BRAF exon 15 mutation. Interestingly, samples of four patients exhibited genetic heterogeneity, enabling us to report this in ISP for the first time.

倒置（施奈德）鼻窦乳头状瘤 (ISP) 是一种源自鼻腔鼻道粘膜的肿瘤，其特征是局部侵袭性生长、复发趋势和与鼻窦癌相关。ISP 的病因尚不清楚。最近，在 ISP 和 ISP 相关的鼻窦癌中报道了癌基因EGFR 的外显子 19 和 20 中的相同突变。然而，尚不清楚重复出现的 ISP 是否在不同时间点显示相同的EGFR突变，或者这些突变在整个 ISP 样本中是否相同。我们使用 Sanger 测序测试了来自 40 名患者的 60 份福尔马林固定石蜡包埋 ISP 样本的EGFR外显子 19 和 20以及BRAF外显子 15 的突变. 总体而言，22 名患者的 32 份样本显示EGFR外显子 20突变，而 18 名患者的 28 份样本未显示突变。在任何样品中均未发现EGFR外显子 19 的突变。四名患者的四份样本显示BRAF外显子 15 突变。有趣的是，四名患者的样本表现出遗传异质性，这使我们能够首次在 ISP 中报告这一点。