It originates from Kulchitsky cells in the submucosal glands of the trachea and bronchus. It is a malignant epithelial tumor consisting of mucous cells, squamous cells and intermediate cells (three cellular components) in a solid, glandular or cystic arrangement, as defined by the WHO. metastasize. It accounts for 0.1% to 0.2% of primary lung cancer and is less malignant than primary bronchopulmonary cancer. Bronchial mucous epidermoid carcinoma can be divided into high-grade and low-grade types based on histological type and ultrastructure. Necrosis and mitosis are only seen in high-grade mucous epidermis-like carcinoma, while low-grade mucous epidermis-like carcinoma rarely metastasizes. High-grade mucinous epidermodysplasia-like carcinoma has a high metastatic potential. LiCH et al. reported that two patients with low-grade mucous epidermis-like carcinoma of the bronchus were successfully treated by tracheoscopic Nd-YAG laser, suggesting that tracheoscopic intervention may be an effective alternative treatment for patients with mucous epidermis-like carcinoma of the bronchus. Bronchial mucous epidermis-like carcinoma, mainly originates from the small mucus glands of the bronchial tree. Cytogenetic studies have revealed that the occurrence of bronchial mucous epidermis-like carcinoma is associated with t(11;19) chromosomal translocations and MECT1-MAML2 (mucoepidermoid carcinoma translocated 1Cmastermind-like 2, MECT1-MAML2) fusions. The most common chromosomal translocation is t(11;19)(q21;p13). t(11;19)(q21;p13) chromosome involves two genes, MECT1 and MAML2, located at 19p13 and 11q21, respectively. this translocation produces a new fusion product, MECT1-MAML2. it fuses exon 1 of MECT1 with exons 2-5 of MAML2. The MECT1-MAML2 fusion product blocks the Notch and CREB (cAMP response element-bindingprotein) signaling pathways by interfering with normal Notch signaling mechanisms and independently activating Notch target genes and multiple cAMP/CREB transcripts without any exogenous signal. CREB) signaling pathway and induce tumor formation. In addition, the MECT1-MAML2 fusion product has a specific role in upregulating EGFR ligand dual-regulatory proteins. In addition, Barrett et al. reported different chromosomal translocations t(1;11)(p22;q13), leading to a mechanism of tumorigenesis. The cyclin D1 is located at 11q13, so the authors speculated that the translocation may cause overexpression of cyclin D1, leading to tumor formation. Indeed, immunohistochemical analysis of anti-cell cyclin D1 showed diffuse strong staining in tumor cells. However, a recent report showed that only 20% of mucous epidermis-like carcinomas had cyclin D1 overexpression, suggesting that other factors or genetic abnormalities, such as t(11;19)(q14-21;p12) or t(11;19)(q21;p13), but not t(1;11)(p22;q13), may be present, leading to the development of mucous epidermis-like carcinomas. Third, clinical characteristics of bronchial mucous epidermis-like carcinoma, the age of onset is between 3 and 78 years, 50% of patients are less than 30 years old, and the onset is equal in both sexes. yousem and Hochholzer reported that patients with low-grade malignant bronchial mucous epidermis-like carcinoma are more common in women, and more than half of the patients are under 30 years old, while 70% of patients with highly malignant bronchial mucous epidermis-like carcinoma are older than 30 years old. Most of the documented cases are case reports or small sample populations. This tumor is also a common endobronchial tumor in pediatrics. Mucous epidermoid carcinoma has been reported to account for 10% of pediatric lung cancers. The presence of congenital developmental malformations, such as unilateral pulmonary hypoplasia, has also been reported in patients with mucous epidermoid carcinoma of the lung. Mucous epidermoid carcinoma of the lung occurs in 10% of the main bronchi, 75% of the segmental and lobar bronchi, and 15% of the periphery, with slightly more on the right than on the left. Since mucous epidermodysplasia carcinoma of the bronchus often involves the large airways, its clinical manifestations are signs and symptoms of irritation or obstruction of the large airways, including cough, hemoptysis, bronchitis, shortness of breath, fever, chest pain, and pestle finger is rare. Lymphatic and hematologic metastases have been reported for mucinous epidermoid carcinoma. The common sites of metastasis are regional lymph nodes (48%), and other sites include lung (25%), bone marrow (25%), distant lymph nodes (18%), adrenal glands (14%), brain (14%), and skin (14%). In addition, it has been reported that mucinous epidermis-like carcinoma can metastasize to skeletal muscle. Imaging manifestations usually include pneumonia, pulmonary atelectasis, middle lobe syndrome and pleural effusion. Mucinous epidermoid carcinoma has no specific manifestation on chest X-ray. It may appear as arcuate nodules or masses in the lung, and some patients may have combined or only pulmonary inflammation and/or pulmonary atelectasis, while some other patients have no positive findings. CT scan shows tumors in the trachea and bronchi with smooth edges, clear boundaries, oval or lobulated nodules or masses, and mainly growing into the lumen. The long axis of the tumor mostly follows the direction of bronchial branches. The long axis of the tumor mostly follows the direction of bronchial branches. Few of them belong to peripheral type, with smooth or lobulated margins and generally without liquefaction and cavity. The tumor density is relatively homogeneous, and the tumor shows mild to moderate enhancement after enhancement scan. The incidence of intra-tumor calcification is higher than that of bronchial lung cancer. The incidence of intra-tumor calcification is 14% higher than that of the common primary lung cancer. Scattered punctate calcification within the tumor is one of its diagnostic features. ④Indirect signs include: bronchial mucus embolism formation, obstructive pneumonia, pulmonary atelectasis, emphysema, and crescentic gas shadows that can be seen around the mass. All of the above signs are caused by the growth of the mass in the lumen of the trachea and bronchus, completely or incompletely obstructing the trachea. ⑤ About 2% of low-grade malignant and 15% of highly malignant mucinous epidermoid carcinoma will have local lymph node metastasis. V. Bronchoscopic manifestations Bronchial mucous epidermoid carcinoma mainly occurs in the large airways, including the trachea, main bronchi, lobar bronchi, and occasionally involves the bronchi of the lung segment. It usually presents as a luminal exophytic mass with a sessile broad-based polypoid mass attached to the tracheal wall or as a well-structured myxoid body, some of which are cauliflower-like. The tumors are pink to brown in color, usually with cystic changes and a glossy mucous-like appearance. The size of the tumor ranges from a few millimeters to 6 cm, with an average size of 2.2 cm. The distal bronchus is usually filled with a large amount of intraluminal mucus-like material. Diagnosis and differential diagnosis (a) Diagnosis of bronchial mucous epidermis-like carcinoma can be confirmed by chest X-ray, CT, bronchoscopy and other means. Bronchoscopy can not only directly observe the tumor in the bronchial lumen, but also facilitate to take biopsy, which is a more accurate means to diagnose the disease. Determination of relevant molecular biological changes can also provide a basis for diagnosis. For example, the MECT1-MAML2 fusion gene and its expression product can be sensitively detected by chromosome in situ hybridization (FISH) and RT-PCR techniques. This not only facilitates the determination of tumor malignancy, but also allows differentiation of bronchial mucous epidermoid carcinoma from non-small cell lung cancer. Histologically, this tumor originates from the submucosal glands of the bronchial wall and is a type of salivary gland type carcinoma. Mucous epidermodysplasia-like carcinoma consists of three types of cells: mucous cells, squamous cells and intermediate type cells. These three types of cells are composed of different shapes in different proportions, including glands, tubules, cysts, nests and solid areas. Mucus-secreting cells can have different shapes, including columnar, cup-shaped, cuboidal, and hyaline, with lightly stained cytoplasm, weak basophilia, nuclei residing on one side, mucus granules visible inside the cells, and large amounts of mucus visible outside the cells. Squamous cells can be mixed with mucus-secreting cells and intermediate cells, and can form cancer nests. There were intercellular bridges between squamous cells, but there were no keratinized beads because of incomplete keratinization. Intermediate cells are usually not specifically differentiated, often polygonal, with medial or off-center nuclei and double-stained or mildly eosinophilic cytoplasm. Intermediate cells are often located in the periphery of the gland or form nests. The tumor may be separated into lobular structures of different sizes by interstitial fibrous tissue. In tumors, the different proportions of these three cell types determine the grading of the tumor. Well-differentiated tumors are usually polypoid in the bronchi and are in close contact with the adjacent submucosal salivary glands. Other features of bronchial mucous epidermoid carcinoma include calcification and marked lymphomatous hyperplasia. (1) Low-grade malignant carcinoma: In the area of lamellar epidermis-like cells, focal clusters of mucous cells are common, or lined in the lumen formed by epidermis-like cells, or glands composed of mucous cells of different sizes and morphologies, scattered in the area of solid cells, and cancer cell division is rare. In hypodifferentiated cases, the mass often grows along the bronchial wall, often irregularly, and invades adjacent lung tissues. (2) Moderately differentiated type (moderately malignant) is between high and low differentiation, with predominantly intermediate and epidermis-like cells, mild to moderate heterogeneity, mostly forming solid carcinoma nests, with fewer cystic cavities. (3) Highly malignant carcinoma is rare, mainly composed of epidermis-like cells, with fewer mucous cells. Some of them can be seen as mucus-filled cystic cavities. The heterogeneity of the two cell types is obvious, and nuclear division images and necrosis are easily seen. The low malignancy (highly differentiated) should be distinguished from mucinous adenoma and cylindroma, and the high malignancy (low differentiation) should be distinguished from adenosquamous carcinoma. (2) Differential diagnosis ①Mucinous cystic adenocarcinoma site: Low malignant mucinous epidermoid carcinoma is located in the central region of the hilum and grows like a polyp in the bronchial cavity, infiltrating the surrounding lung parenchyma, but the boundary is generally clear. In contrast, mucinous cystic adenocarcinoma is located in the periphery of the lung, and the mucus diffusely infiltrates the surrounding lung tissue with unclear borders; squamous cells and intermediate cells can be seen in low-grade malignant mucinous epidermis-like carcinoma, but not in mucinous cystic adenocarcinoma; the columnar epithelial heterogeneity of the covered cyst wall is not obvious in low-grade malignant mucinous epidermis-like carcinoma, and clumps of heterogeneous mucinous cells are not seen in the mucus lake. In contrast, mucinous cystic adenocarcinoma had larger columnar cells in the overlying cyst wall and nuclear heterotypic plexiform with heterotypic mucinous cells. ②Lowly differentiated squamous cell carcinoma highly malignant mucous epidermis-like carcinoma carcinoma tissue was mainly composed of intermediate cells with few well-differentiated squamous cell nests and glandular components, which did not show a stratified structure, while the nests of lowly differentiated squamous carcinoma carcinoma showed a stratified structure; highly malignant mucous epidermis-like carcinoma mucus-rich cells were more common, while only a few mucus was seen in the plasma of lowly differentiated squamous carcinoma carcinoma cells. Bronchial carcinoid tumor is rich in blood vessels, and enhancement scan shows significant enhancement, while bronchial mucous epidermis-like carcinoma has only mild enhancement. Treatment (a) Surgery is currently considered to be the only effective treatment method, and radiotherapy is not very sensitive. Surgical methods include lobectomy, sleeve resection, partial resection, lung segment resection, etc. Surgery for low-grade malignant mucous epidermoid carcinoma is effective, and most patients will not have recurrence after complete resection of the tumor, even if it is palliative resection, they can survive with the tumor for many years after surgery. Since mucinous epidermoid carcinoma is mostly of low malignancy, the surgical approach should preserve normal lung function as much as possible under the premise of ensuring radical resection of the tumor, and thus tracheobronchoplasty arises. Bronchial sleeve resection can preserve the lung parenchyma as much as possible, but it is selective for the location of the tumor, and it is difficult to perform sleeve resection if the location of the lesion is far from the main bronchus. Thoracoscopic-assisted surgery is simple, less traumatic, and can significantly shorten the hospitalization time, and has the same clinical effect as open-heart surgery. (2) Radiotherapy is used as adjuvant therapy for patients who cannot undergo surgical resection or after surgery to further control tumor development. Low-grade malignant tumors can be treated without radiotherapy after surgery. High-grade malignant tumors have poor prognosis and should be treated as non-small cell lung cancer. Patients with incomplete resection or progressive tumors may be treated with adjuvant chemotherapy or radiation therapy. The available chemotherapeutic agents are cisplatin, tamsulosin, gemcitabine, adriamycin and pemetrexed. For early-stage tumors, adjuvant chemotherapy can be taken appropriately after surgery to prolong overall survival and recurrence-free survival; for advanced-stage tumors, the combined treatment method of surgery plus postoperative radiotherapy is mostly used, but it does not necessarily improve overall survival. (iii) Bronchoscopic treatment Bronchoscopy is an important option to obtain preoperative histological diagnosis. In some cases, polypoid tumors may appear to be completely intraluminal and can be resected microscopically. However, performing bronchoscopic resection does not cure the majority of patients with central lesions because the tumor may invade or penetrate the bronchial wall. Bronchoscopic resection may be considered in the following clinical situations: patients with central airway obstruction who cannot tolerate surgery or patients who refuse surgery and advanced patients with distant metastases, where bronchoscopic tumor resection is a valuable palliative treatment. Tracheoscopic resection of obstructive lesions helps the surgeon to set the most appropriate surgical procedure. In highly selected patients with polypoid bronchial carcinoid tumors, tracheoscopic resection may prolong recurrence-free survival. These patients present with an intraluminal polypoid lesion, a clear view of the distal tumor, no evidence of bronchial wall involvement, and no evidence of lymph node metastasis on high-resolution CT. For mucous epidermodysplasia-like carcinoma, tracheoscopy can be used with CO2 freezing, APC, local drug injection in the tracheal lumen, radiotherapy particle implantation, and photodynamic therapy. See the relevant sections for details. For confined polypoid tumors that are completely intraluminal, direct laparoscopic resection with tracheal sleeve, carbon dioxide freezing, or direct cautery resection with APC can be performed, and the root of the tumor can be cauterized with APC, which can destroy the tumor tissue and achieve the purpose of hemostasis. If the resected polypoid tumor is low-grade mucous epidermis-like carcinoma, regular tracheoscopic examination and carbon dioxide freeze thawing treatment should be performed. If the polyp-like tumor is a high-grade mucous epidermis-like carcinoma, surgery is recommended after removing the tumor and for those who do not want to operate or have no surgical guidelines, local injection of chemotherapy drugs or radiotherapy particle implantation can be performed at the root of the tumor. For a small number of large intraluminal tumors that invade the tracheal wall, the risk of bleeding is high when APC is performed directly, so generally the tumor tissue can be removed by trap or CO2 freezing first, and the remaining tumor tissue can be cauterized by APC. If there is no surgical guideline, the subsequent treatment is local injection of chemotherapeutic drugs or radiotherapy particle implantation treatment, and can also be combined with microscopic photodynamic therapy. (iv) Molecular targeted therapy1, EGFR-TKI treatment HanSW and Rossi G both reported that mucinous epidermis-like carcinoma of the lung had a good clinical response to the EGFR-TKI gefitinib. Interestingly, this tumor lacks sensitive EGFR mutations (exon 19 deletion or exon 21 mutation). In fact, one study found that: EGFR mutations rarely occur in mucinous epidermis-like carcinoma at any site. However, many data suggest that EGFR-sensitive mutations are important in terms of clinical efficacy of TKI therapy and selection of appropriate patients.CRTC1CMAML2 is a characteristic manifestation of mucinous epidermoid carcinoma of the lung and plays an important role in tumorigenesis. This fusion gene, may be the reason why the tumor is sensitive to TKI treatment. In vitro experiments confirmed this hypothesis. Han et al. found that the H-292 lung mucinous epidermoid carcinoma cell line was highly sensitive to gefitinib, but was EGFR wild type. Importantly, t(11;19) and CRTC1CMAML2 were present in the H-292 cell line. another mucinous epidermal-like carcinoma cell line, H3118, was similarly present. The reason for this may be related to the fact that CRTC1CMAML2 fusion gene can upregulate EGFR ligand double-regulated protein. TSP-1 is found in platelet granules and extracellular matrix, and belongs to the TSP family. therapy. It was found that TSP-1 was highly expressed in mucous epidermis-like carcinoma, and its expression level was negatively correlated with neovascularization. tSP-1 can inhibit neovascularization and tumor growth, and is likely to be a novel biologic therapy for bronchial mucous epidermis-like carcinoma. The prognosis of bronchial mucous epidermoid carcinoma is related to many factors, such as tumor histotype, tumor size, presence of lymph node metastasis, surgical method, whether there is cancer residue in the surgical margin, postoperative complications, age and patient’s physical status, etc. A study conducted by ChinCH et al. on the prognosis of pulmonary mucous epidermoid carcinoma found that tumor stage was an independent risk factor affecting patient’s prognosis, with stage IA The prognosis of patients with stages IA, IB, and IIB (10-year survival rate of 87.5%) was significantly better than that of patients with stages IIIB and IV (1-year survival rate of 28.6%; 2-year survival rate of 0, P=0.001). Histological grade was also an important factor affecting prognosis, with patients with low-grade tumors having a better prognosis (1-year survival rate 80%; 5-year survival rate 57.1%) than patients with high-grade tumors (1-year survival rate 20%) (P = 0.035), but not as an independent risk factor for predicting prognosis (P = 0.054). The effect of histologic grading on patient prognosis was also confirmed by Yu Changhai et al. They retrospectively summarized 34 cases of surgically resected primary pulmonary mucinous epidermoid carcinoma, of which 23 cases of low-grade malignant pulmonary mucinous epidermoid carcinoma, one with hilar lymph node metastasis, had survival rates of 100%, 100%, and 90.9% at 1, 3, and 5 years, respectively; 11 highly malignant patients with 63.64% lymph node metastasis and postoperative The survival rates at 1, 3, and 5 years were 50.0%, 14.3%, and 0. In addition, the older the patient, the more likely he or she was to develop high-grade tumors, and children had a better prognosis than adults. From a molecular biological point of view, the presence of the MECT1-MAML2 fusion gene is also a factor affecting prognosis, and Behboudi et al. found that those positive for MECT1-MAML2 fusion had a lower risk of local recurrence of metastasis or tumor-related death than those negative (P=0.0012). When only tumor-related death was considered, the median survival of fusion-positive individuals was >10 years, while the median survival of negative individuals was only 1.6 years. This shows that the presence of the MECT1-MAML2 fusion gene is also an important factor affecting prognosis.