INTRODUCTION The classical micropapillary (MIP) pattern is defined in the 2015 WHO classification as tumor cells growing in papillary tufts forming florets that lack fibrovascular cores and it is associated with poor prognosis. We observed a novel pattern that we termed to be a filigree MIP pattern and investigated its relationship to the classical MIP pattern. METHODS Filigree pattern was defined as tumor cells growing in delicate lace-like narrow stacks of cells without fibrovascular cores. We required at least 3 piled-up nuclei from the alveolar wall basal layer with a breadth of up to 3 cells across. To assess the relationship of the filigree vs classical MIP pattern, we documented their frequency in the context of clinical and pathologic characteristics of 1468 Stage I invasive adenocarcinomas including survival analysis using cumulative incidence of recurrence (CIR) by competing risks. RESULTS We observed the filigree MIP pattern in 35% of cases. By including the filigree pattern as MIP, we identified 57 more MIP predominant cases in addition to the previously diagnosed 87 MIP predominant adenocarcinomas. These 57 cases were reclassified from papillary (n=37), acinar (n=16), and solid (n=4) predominant adenocarcinoma, respectively. Of the 144 MIP predominant adenocarcinomas, filigree predominant MIP (n=78) showed a poor prognosis like classical predominant MIP (n=66) (p=0.464). In addition, like classical MIP (p=0.010), even small an amount (≥5%) of filigree MIP was significantly associated with worse CIR (p=0.001) in multivariable analysis. CONCLUSION The frequent association with classical MIP and the similar poor prognosis supports inclusion of the filigree pattern in the MIP subtype.

中文翻译：

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微乳头状腺癌概念的扩展，包括新认识的金丝图案以及基于 1468 个 I 期肺腺癌的经典图案

简介 经典微乳头 (MIP) 模式在 2015 年 WHO 分类中被定义为肿瘤细胞在乳头簇中生长，形成缺乏纤维血管核心的小花，与不良预后相关。我们观察到一种新颖的图案，我们将其称为细丝 MIP 图案，并研究了它与经典 MIP 图案的关系。方法 丝状图案被定义为肿瘤细胞生长在精致的花边状狭窄细胞堆中，没有纤维血管核心。我们需要来自肺泡壁基底层的至少 3 个堆积的细胞核，宽度最多为 3 个细胞。为了评估花丝与经典 MIP 模式的关系，我们在 1468 个 I 期侵袭性腺癌的临床和病理特征背景下记录了它们的频率，包括使用竞争风险的累积复发率 (CIR) 进行生存分析。结果 我们在 35% 的病例中观察到细丝 MIP 图案。通过将花丝图案纳入 MIP，除了先前诊断的 87 例 MIP 为主的腺癌之外，我们还确定了 57 例 MIP 为主的病例。这 57 例病例分别从乳头状腺癌 (n=37)、腺泡状腺癌 (n=16) 和实性腺癌 (n=4) 重新分类。在 144 例 MIP 为主的腺癌中，花丝为主的 MIP (n=78) 与经典为主的 MIP (n=66) 一样，预后较差 (p=0.464)。此外，与经典 MIP (p=0.010) 一样，在多变量分析中，即使少量 (≥5%) 的细丝 MIP 也与较差的 CIR (p=0.001) 显着相关。结论 与经典 MIP 的频繁关联以及类似的不良预后支持将花丝图案纳入 MIP 亚型。