As one of the most common target organs for hematogenous spread from diverse cancers, biopsy interpretation of lung tumors is complicated by the challenging question of primary versus metastatic and by frequent entrapment of native respiratory glands. Nevertheless, the literature dealing with this issue is surprisingly sparse and no single study has been devoted to this topic. We reviewed 47 surgical lung specimens of non-epithelial neoplasms (38 metastases, mainly from sarcomas and 9 primary lesions) for frequency and pattern of intralesional epithelial entrapment. Respiratory epithelium entrapment was noted in 23/47 (49%) cases (diffuse in 15 and peripheral in 8). Entrapped glands frequently showed prominent regenerative and reactive changes mimicking neoplastic glands. Based on cellularity of the mesenchymal component and the extent, distribution and shape of entrapped respiratory glands, four morphological patterns were recognized: paucicellular sclerosing low-grade neoplasms containing leaflet-like glands indistinguishable from adenofibroma and fibroepithelial hamartomas (n = 11), and biphasic cellular lesions mimicking adenomyoepithelioma (n = 1), biphasic synovial sarcoma (n = 2), and pleuropulmonary blastoma (n = 1). Only a single genuine pulmonary adenofibroma was identified. This study highlights frequent respiratory epithelium entrapment in diverse non-epithelial lung tumors, both primary and metastatic. Recognition of this finding and use of adjunct IHC combined with clinical history should help to avoid misinterpretation as primary pulmonary biphasic neoplasm or as harmless adenofibroma. The vast majority of morphologically defined lung adenofibromas represent adenofibroma-like variants of histogenetically diverse entities so that a diagnosis of adenofibroma should be rendered only very restrictively and then as a diagnosis by exclusion.

作为各种癌症的血源性扩散的最常见靶器官之一，肺肿瘤的活检解释因原发性与转移性的挑战性问题而变得复杂并经常困住本地呼吸道。然而，有关该问题的文献非常少，而且没有单独的研究致力于该主题。我们回顾了47例非上皮性肿瘤的外科手术肺标本（38个转移灶，主要来自肉瘤和9个原发灶），以了解病灶内上皮截留的频率和模式。在23/47（49％）的病例中发现呼吸道上皮截留（扩散15例，外周扩散8例）。被困的腺体经常表现出显着的再生和反应性变化，类似于肿瘤性腺体。根据间充质成分的细胞性以及被夹带的呼吸腺的程度，分布和形状，可以识别出四种形态学模式：n  = 11）和模仿腺肌上皮瘤（n  = 1），双相滑膜肉瘤（n  = 2）和胸膜肺母细胞瘤（n = 1）。仅鉴定出一个真正的肺腺纤维瘤。这项研究突出了原发性和转移性的多种非上皮性肺肿瘤中频繁的呼吸道上皮截留。认识到这种发现和使用辅助IHC结合临床病史应有助于避免误解为原发性肺部双相性肿瘤或无害腺纤维瘤。绝大多数形态学上确定的肺腺纤维瘤代表了组织遗传学上不同实体的腺纤维瘤样变体，因此对腺纤维瘤的诊断应严格限制，然后通过排除进行诊断。