肺腺体前驱病变(不典型腺瘤样增生、原位癌)、微浸润癌的概念及影像学表现
目前,全球范围内整体人群第一高发恶性肿瘤是肺癌。得益于影像学检查的准确和各种治疗手段的有效性,肺癌的整体生存有了明显的改善,特别是肺癌的早期状态,术后切除可以得到根治的效果。
早期肺癌定义不同,大致包括可以手术切除,积极治疗可取得良好效果的意思,特别是原位癌和微浸润癌,是基于病理诊断,也就是显微镜下的肿瘤的生长状态。影像学,特别是高分辨CT(High Resolution CT)在特定的条件下可以理解为肺部病变病理的大体表现,也就是影像与病理紧密相关。
1. 肺的癌前病变 Lung cancer prodromal lesionsins
Early lesions should not be regarded as conventional invasive adenocarcinomas and can be observed rather than surgically resected.
    • 腺体前驱病变,Precursor glandular lesions, 又分为非典型腺瘤样增生 (AAH) 和原位腺癌 (AIS),二者与肺腺癌相关。atypical adenomatous hyperplasia (AAH) and adenocarcinoma in situ (AIS).
    • 支气管恶性前病变,Bronchial premalignant lesions,是肺鳞状细胞癌的前体,precursors of lung squamous cell carcinoma and are a risk factor for developing lung cancer at the lesion site or elsewhere in the lung.
    • Dermatomyositis, an idiopathic connective tissue disease, has been associated with malignancy, including breast, ovarian, lung, and colon cancer. 与肺恶性肿瘤相关(包括乳腺癌、卵巢癌、肺癌和结肠癌)的特发性皮肌炎(结缔组织疾病)
    2. 肺腺体前驱病变 Precursor glandular lesions
    肺腺体前驱(precursor)是腺癌前的状态,是病理学概念,发生在肺泡上皮,包括两种状态,AAH和AIS,前者指肺腺癌没有发生,后者指发生但没有出现浸润的状态,与肺腺癌的早期病变(Early lesions)部分重合。
    3. 非典型腺瘤样增生 Atypicaladenomatous hyperplasia
    非典型腺瘤样增生是肺泡上皮细胞的局灶性轻度到中度的非典型增生(异型性),排列密集,直径通常<5mm。CT表现为纯磨玻璃结节(pGGN),AAH被认为是肺腺癌的最早阶段,可能进展为原位腺癌(AIS),但进展风险低,多数可长期稳定,需定期CT随访(如每年1次)。
    AAH体积小,密度低。当密度增高,而且体积增大时,就可能发展成AIS;当出现实性成分比小于50%时,就可能是MIA;如果实性成分比大于50%,则可能是IA。
    Atypicaladenomatous hyperplasia (AAH) is the first putative precursor lesion of adenocarcinoma of the lung. On CT imaging, AAH usually presents as a well-defined round pure GGN < 5 mm in diameter.
    4. 原位腺癌 Adenocarcinoma in situ
    原位癌字面意思容易和原发肿瘤混淆,是病变局限,没有扩散,指病变直径≤30mm,内基底膜内生长,没有间质、血管或胸膜侵犯,即未见浸润性腺癌,细胞类型多为非黏液性,变现为磨玻璃结节;黏液性AIS非常罕见,表现为实性结节。
    • Adenocarcinomain situ, AIS, histopathologically≤30 mm, noninvasive lepidic growth, which at CT is usually nonsolid. 
    • Non-mucinous AIS usually appear as pure GGNs; however, owing to the presence of collapsed alveoli they can be seenas part-solid nodules. 
    • Mucinous AIS can appear either as a solid nodule or as consolidation. 
    按照 WHO 2021版的分类,AIS不属于肺癌范畴,也就是说生物学行为与微小浸润腺癌和浸润性腺癌不同。对于AIS,影像诊断有风险,有些肺结节影像诊断是原位癌,而病理诊断是微浸润腺癌。此外,小标本或细胞学对AIS诊断也有局限性,AIS的病理诊断标本应为手术全切病灶的大标本。
    5. 微/小浸润腺癌 Minimally invasive adenocarcinoma
    微浸润腺癌,MIA, Minimally invasive adenocarcinoma,指≤30mm的孤立的腺癌,以上皮结构为主,已有基底膜的突破,浸润灶的范围≤5mm‌。大部分是非粘液性MIA,CT影像可能是纯磨玻璃结节,或者混合磨玻璃结节/部分实性结节/非实性结节,中心有小于5 毫米的实性部分。手术切除后治愈率接近100%,极少复发或转移。
    • MIA, histopathologically ≤30 mm and predominantly lepidic growth that has 5-mm or smaller invasion, which at CT is mainly nonsolid but may have a central solid component of up to approximately 5 mm.
    • non-mucinous MIA usually appears in the form of a pure GGN or as a PSN. 
    • Mucinous MIA is far less frequently observed and predominantly presents as a solid nodule.
    6. 肺腺癌贴壁生长 lepidic growth
    贴壁样生长/附壁生长,lepidic growth,是指肿瘤细胞沿着原有的肺泡结构贴壁生长,取代原有肺泡上皮的生长方式‌,‌见于早期肺腺癌,如原位腺癌(AIS)和微小浸润型腺癌(MIA)‌。
    Adenocarcinoma with lepidic growth is a subtype of adenocarcinoma, accounts for about 5% of lung carcinomas but up to 20% are histologically mixed adenocarcinoma and BAC.
    The subclassification of adenocarcinomas of the lung has largely remained unchanged since 2015 with invasive adenocarcinomas classified as MIA, invasive nonmucinous adenocarcinoma, invasive mucinous adenocarcinoma (IMA), colloid adenocarcinoma, fetal adenocarcinoma, or enteric-type adenocarcinoma. These are distinguished from the precursor glandular lesions atypical adenomatous hyperplasia or AIS. Invasive nonmucinous adenocarcinomas are the most common subtype of lung cancer and consist of malignant epithelial tumors with morphologic or immunohistochemical evidence of glandular differentiation and not fulfilling criteria for any other type of adenocarcinoma.
    扩展阅读:
    1. https://jtd./article/view/2833/html
    2. https://pubmed.ncbi.nlm./38223102/
    3. https://www./figure/a-Atypical-adenomatous-hyperplasia-demonstrated-as-focal-pure-GGN-b-Adenocarcinoma-in_fig3_371662102
    4. https://www./figure/Computed-tomography-image-shows-vascular-convergence-blue-arrows-pleural-retraction_fig3_375798779
    5. https:///term/bronchial-adenoma
    6. https://www./media/1185096/view/small-cell-lung-cancer-ct-scan
    7. https://www./what-is-early-stage-lung-cancer-2249025
    8. https://journal./article/S0012-3692(16)60780-8/abstract
    9. https://www./cancer/types/lung-cancer/detection-diagnosis-staging/staging-sclc.html
    10. https://www./journals/oncology/articles/10.3389/fonc.2021.667111/full
    11. https:///wp-content/uploads/2021/12/Early-Stage-Lung-Cancer-B5-Final.pdf
    12. https://pubs./doi/10.1148/radiol.220585
    13. https:///lungs/cancer-adenocarcinoma-with-lepidic-growth/
    14. https://www./science/article/pii/S1556086421033165