Invasive mucinous adenocarcinoma (IMA) of the lung shares some clinicopathological features with mucinous carcinoma of other organs, such as the ovary. Sarcoma-like lesions, called mural nodules, have been reported in the cystic walls of ovarian mucinous tumors. In this study, we analyzed 213 surgically resected cases of IMA of the lung to determine whether similar mural nodule–like lesions were present. We considered abrupt discrete lesions composed of dedifferentiated tumor cells as mural nodule–like lesions. Of 213 IMAs, we identified 11 tumors with mural nodule–like lesions that were histologically categorized into three subtypes similar to those in the ovary. The sarcomatoid and anaplastic carcinoma–like nodules were composed of spindle cell proliferations and polygonal undifferentiated carcinoma, respectively. Sarcoma-like lesions mimicked sarcomatoid nodules, but the spindle cell proliferations were considered a fibroblastic reaction to the scattered, isolated clusters of tumor cells. Molecular analysis of the components of differentiated IMAs and mural nodule–like lesions revealed a clonal relationship, suggesting a spectrum of tumors with different histology. Clinicopathologically, an older age, the male sex, and smokers were significantly associated with IMAs with mural nodule–like lesions. Notably, patient outcomes were unaffected by the presence or absence of these lesions. Our findings demonstrated that IMA of the lung rarely develops mural nodule–like lesions (11 of 213, 5%). Despite a histological impression of clinical aggressiveness, there was no clear trend in patient outcomes, suggesting that pathologists should avoid overstating this mural nodule–like lesion.

浸润性粘液腺癌肺 (IMA) 与其他器官（如卵巢）的粘液癌具有一些临床病理学特征。肉瘤样病变，称为壁结节，已在卵巢粘液性肿瘤的囊性壁中报道。在这项研究中，我们分析了 213 例手术切除的肺 IMA 病例，以确定是否存在类似的壁结节样病变。我们将由去分化肿瘤细胞组成的突然离散病变视为壁结节样病变。在 213 个 IMA 中，我们确定了 11 个具有壁结节样病变的肿瘤，这些肿瘤在组织学上被分为与卵巢相似的三个亚型。肉瘤样和间变性癌样结节分别由梭形细胞增生和多边形未分化癌组成。肉瘤样病变模仿肉瘤样结节，但梭形细胞增殖被认为是对分散的、孤立的肿瘤细胞簇的成纤维细胞反应。对分化的 IMA 和壁结节样病变成分的分子分析揭示了克隆关系，表明具有不同组织学的一系列肿瘤。在临床病理学上，年龄较大、男性和吸烟者与具有壁结节样病变的 IMA 显着相关。值得注意的是，患者的预后不受这些病变存在与否的影响。我们的研究结果表明，肺 IMA 很少发展为壁结节样病变（213 例中有 11 例，5%）。尽管存在临床侵袭性的组织学印象，但患者预后没有明显趋势，这表明病理学家应避免夸大这种壁结节样病变。