The tumor is intimately associated with a large bronchus, and probably arose from the bronchial wall. The neoplastic cells are spindled with fascicular architecture and a small and varying amount of myxoid substance in the background. Cytology is that of a benign neoplasm. Differential diagnoses include neuroma and leiomyoma, and immunohistochemical stains can certainly help. In my opinion, the nuclear size is small and more consistent with that of Schwann cells than with smooth muscle cells. S100, sm muscle actin and neurofilaments should suffice. If the lung tissue has other small foci of spindle cell proliferation, then lymphangioleiomyomatosis should be considered. This is a condition related to PEComa, so melanocytic markers are positive. Without the help of immunohistochemical stains, I cannot be sure what this is. My first choice would be a benign neuroma, but I have never seen one at this location. I don't think solitary fibrous tumor, GIST, carcinoid, or spindle cell carcinoma are in the differential diagnoses. Difficult and unusual case this is.

 谢谢马老师精彩而全面的发言。

 赞赏并谢谢马老师的精彩发言。

首先肯定是良性的。

图片被抢眼看去，的确像是平滑肌瘤或神经鞘膜瘤。但细细看来，本例结节在支气管壁生长并向管腔突出，由梭形细胞构成。间有少量腺体混杂于梭形细胞之间，呈随机分布。在瘤结节靠近外膜侧也可见到这样的腺体。因此，考虑是一个错构瘤，或（由平滑肌和腺体构成的）腺肌瘤。

个人意见，仅供参考！

 同意