Inverted papilloma is a common benign tumor in nasal cavity and paranasal sinuses. It is more common that paranasal sinuses and nasal cavities are invaded at the same time, and the incidence of bilateral sinus cavities is low. The same symptoms of the disease are nasal congestion, headache, headache and abnormal sense of smell. Nasal examination is similar to nasal polyps, which is easy to be confused. Inverted papilloma is one of the most common benign tumors in nasal cavity and paranasal sinuses. Although inverted papilloma of nose is a benign tumor, its special biological characteristics make it different from other benign tumors. First, inverted papilloma of nose shows local invasive growth, which often destroys the bone around the tumor and even affects the orbit and skull. Secondly, the malignant rate of nasal inverted papilloma is 5% ~ 15%. Thirdly, it is easy to occur after surgical resection, and the recurrence rate is 5% ~ 30%. Postoperative tumor recurrence is related to surgical techniques and tumor biological behavior. Although it is reported that the tumor has many new growth characteristics, the main reason for recurrence is postoperative residue. Therefore, surgical resection of tumor is still the main method to prevent recurrence. 1 The etiology of nasal inverted papilloma and human papillomavirus nasal inverted papilloma is still unknown. However, studies have shown that human papillomavirus (HPV) plays an important role in the occurrence of nasal inverted papilloma. As early as 1987, it was reported that the incidence of human papillomavirus in nasal inverted papilloma was 32%. Inverted papilloma of nose also plays a role in malignant transformation of tumor. In addition, the expression of growth factors and their related receptors related to various tumors increased in inverted papilloma of nose. Include epidermal growth factor and its receptor; Transforming growth factor and its receptor, etc. The high expression of these factors is closely related to the malignant transformation of tumors. Recent studies show that nasal inverted papilloma type 6/1 1 is positive in nearly half of nasal inverted papillomas. The nasal inverted papilloma 16/ 18 was positive in nearly 1/3 nasal inverted papilloma tissues [1]. The characteristics of serum squamous cell carcinoma antigen and inverted papilloma, that is, easy to relapse and canceration after operation, make it very important to follow up closely after operation. However, some special parts are still difficult to be revealed during the follow-up after sinus surgery, and postoperative CT and MRI are also lack of specificity. Therefore, it is very important to find tumor markers. In the detection of 28 cases of nasal inverted papilloma marked by squamous cell carcinoma antigen, it was found that the level of squamous cell carcinoma antigen in 89% patients with nasal inverted papilloma was higher than normal before operation, but decreased after operation. Among them, 4 cases were nasal inverted papilloma, and the antigen level of squamous cell carcinoma in vivo did not decrease continuously after operation, and 3 cases recurred after operation. The results suggest that squamous cell carcinoma antigen may become a tumor marker of nasal inverted papilloma [2]. 3 History of surgical resection of nasal inverted papilloma The surgical resection of nasal inverted papilloma has gone through the following periods: ① Non-endoscopic resection of nasal inverted papilloma. The approach of this method includes intranasal operation and Caldwell-Luc operation through the anterior wall of maxillary sinus. The postoperative tumor recurrence rate was as high as 20% ~ 100%, so it was abandoned. ② The alternative to the previous surgical approach is the extranasal approach, including lateral nasal incision, resection of nasal outer wall, nasal exposure, etc. This surgical method has always been regarded as the gold standard for the treatment of inverted papilloma of nose. But there were postoperative tears, chronic dacryocystitis, eustachian tube dysfunction, local scar and long hospitalization time. (3) With the extensive application of endoscopic sinus surgery, the indications of endoscopic sinus surgery are also expanding. Since 1980s, more and more scholars at home and abroad have begun to treat inverted papilloma of nose with endoscopic technique. 4 classification of inverted papilloma nasal inverted papilloma should be the differential diagnosis of all unilateral nasal and paranasal sinus diseases, although in most cases inverted papilloma is easy to be distinguished from nasal sinusitis. Because inverted papilloma often coexists with nasal polyps or other sinusitis tissues, its papillary manifestations may be covered up, so it is very important to pay attention to differentiation. The controversial focus of endoscopic surgery in the treatment of inverted papilloma of nose is whether the effect of endoscopic surgery is better than that of external nasal approach. But in fact, it is difficult to compare the extranasal approach with the intranasal approach. The main reasons are the great differences in preoperative evaluation, disease range, surgical methods and postoperative follow-up time. In addition, the grading system that has not been widely adopted by most scholars at present is also one of the reasons why clinical research is difficult to compare. Krouse grading system [3] (table 1) is widely used at present. It is suggested that domestic scholars use this system for grading, so as to facilitate the comparison between different studies and to be in line with international standards. The key to evaluate the success of surgical treatment of nasal inverted papilloma before operation is to locate the attachment point and scope of the tumor and completely remove the tumor. CT is one of the most commonly used methods to estimate the tumor range, because it is relatively economical and widely used. CT shows the bony structure well, but it is difficult to distinguish the tumor tissue from the surrounding inflammatory tissue and residual secretions, so CT often leads to overestimation of the tumor range. In addition to CT, MR is also a common method to estimate the tumor range before operation. Generally speaking, in T2 phase, inverted papilloma of nose shows moderate signal, while inflammation around inverted papilloma shows high signal. Inverted papilloma of the nose is often confined to the nasal cavity, and the pathological tissues located in the paranasal sinuses are often high-signal inflammatory tissues and viscous secretions. The combination of CT and MR examination is valuable in evaluating the tumor range (Figure 1). It is rare for tumors to directly invade frontal sinus and sphenoid sinus in clinic. More often, tumors blocked the openings of frontal sinus and sphenoid sinus, and most of them were inflammatory changes rather than real tumors. Occasionally, the tumor will completely occupy the sinus cavity. In a few cases, it is difficult to estimate before operation, and only during operation can the position of tumor root be located very accurately, such as the tumor is located in ethmoid-orbital region and uncinate process. 6. Surgical treatment of nasal inverted papilloma. Complete resection is the most important method to treat inverted papilloma of nose. The comparison between traditional open surgery and modern endoscopic sinus surgery has always been the focus of debate. In recent years, more and more long-term follow-up clinical studies have confirmed that endoscopic sinus surgery is a feasible method. However, there is still a postoperative recurrence rate of 12% ~ 17%, and the recurrence mostly occurs within one year after operation [4 ~ 8]. At present, the scope of endoscopic rhinoplasty for inverted papilloma is mostly determined by the lesion range estimated by preoperative imaging and the tumor range seen during operation. It is very important to locate the basal part of tumor during operation, which is often the key to clean resection of tumor tissue. Tumor tissue is often cut into pieces by a cutter, and it is difficult to cut into pieces at one time. Remove the soft tissue at the bottom of the tumor. If possible, polish the bone at the bottom of the tumor with a diamond drill. During the operation, the normal tissue at the edge of the tumor should be preserved as much as possible, and the sinus should be opened as much as possible to facilitate postoperative follow-up. The scope of endoscopic surgery for nasal inverted papilloma and the choice of surgical methods depend on the location of tumor base, the scope and nature of the tumor (whether it is malignant or not). Surgical methods can be divided into small-scale tumor resection, total sphenoid ethmoidectomy, maxillary sinus (enlarged) inner wall resection, DRAF ⅲ frontal sinus surgery and nasal endoscopic surgery. For kro useⅰⅰ tumor, the tumor is located in the nasal cavity. If the basal part is clearly exposed, simple tumor resection can be performed with sufficient safe margin. After careful inspection, there is no residue. Total ethmoidectomy can be considered for kro useⅱⅱ tumor. On the premise of carefully positioning the cardboard and the anterior skull base, carefully remove all tumor tissues and open the maxillary sinus as much as possible for postoperative follow-up. For tumors invading sphenoid sinus, sphenoid sinus surgery can be performed according to the tumor range. We should be very careful in the operation for nasal inverted papilloma invading the outer wall of sphenoid sinus and the wall of posterior ethmoid sinus to avoid serious complications. In short, inverted papilloma invading the nasal cavity, ethmoid sinus and sphenoid sinus can be completely removed by simple endoscopic surgery [9]. When the tumor tissue spreads to the outer wall, the lower wall and even the front wall of the maxillary sinus, it is often difficult to completely remove it through the middle nasal meatus under the simple nasal endoscope. Although we now have a multi-angle mirror and various angle instruments, including a multi-angle cutter, it is still difficult to completely remove all tumor tissues in the maxillary sinus. At this time, all pathological tissues can be removed by fenestration of the inferior nasal passage or fenestration of the anterior wall of maxillary sinus combined with endoscopic sinus surgery. It is difficult to control the instrument in the surgical field of vision. The treatment of maxillary sinus lesions through the anterior wall and middle nasal meatus is simple and thorough. The difficulty of surgical operation and the size of resection range are related to the size of the window. After opening the window for several hours, the facial numbness is less, but the surgical exposure is poor, so it is difficult to ensure complete resection. When the front window is large, the maxillary sinus is fully exposed, and it is easy to remove all tumor tissues, but it is easy to leave the upper lip numb after operation. Another operation that is very useful for tumors invading maxillary sinus, especially inferior turbinate, is endoscopic maxillary sinus resection. The first incision of the operation starts from the attachment of the front end of the middle turbinate and cuts down along the maxillary ridge to the front end of the lower turbinate. Cut the nasolacrimal duct short after breaking the corresponding bone. Move the outer wall of nasal cavity inward, chisel off the outer wall of nasal cavity horizontally along the nasal base, cut off the rear ends of middle and lower turbinates, and remove the outer wall of nasal cavity. At this time, the maxillary sinus is well exposed, and the tumor tissue in the maxillary sinus can be removed by using a 30 or 70 mirror with a curved pliers or a curved knife. The lateral part of the maxillary sinus, especially the junction between the anterior wall and the anterior and bottom walls of the anterior wall, is difficult to handle. If necessary, the medial part of the anterior wall of maxillary sinus can be removed. On the basis of resection of the inner wall of maxillary sinus, the inner part of the anterior wall of maxillary sinus can be cut in an arc shape, the nasal bone can be raised, the nasal floor can be lowered, the suborbital neurovascular bundle can be preserved, and most of the inner part of the anterior wall of maxillary sinus can be removed. At this time, the fixed anterior nasal endoscope is used to open the anterior nostril, and almost all the walls of the maxillary sinus can be seen directly with a 0 mirror. The maxillary sinus wall can be almost fully treated with various instruments with slightly larger angles, leaving no dead ends. According to the need to decide whether to expand the scope of anterior wall resection. The use of maxillary sinus inner wall resection or extended maxillary sinus inner wall resection is mostly based on the judgment of tumor range during operation, and it is only used when dealing with maxillary sinus lesions that cannot be handled by conventional endoscopic sinus surgery [10, 1 1]. Another site that is difficult to treat under endoscope is the frontal sinus. When the base of nasal inverted papilloma is located in ethmoid sinus and falls into frontal sinus, or the frontal sinus is small and invades nasal inverted papilloma, it can be solved by endoscopic DRAF ⅱ or DRAF ⅲ surgery [12]. When nasal inverted papilloma has a wide range or bilateral frontal sinuses are involved at the same time, draf ⅲ operation can be used to solve it. When the frontal sinus is well developed, the sinus cavity is large, there is tumor invasion, or nasal inverted papilloma breaks through the bone plate and protrudes into the orbit or skull, it is difficult to remove all the diseased tissues by simple endoscopic approach, and it is often necessary to combine endoscopic and extranasal surgery to remove the tumor (Figure 2). For patients with large tumor range before operation, it should be explained that it is possible to treat frontal sinus lesions through intranasal and extranasal approaches before operation. Whether it is a simple endoscopic approach or an intranasal or extranasal approach, the opening of frontal sinus should be enlarged as much as possible for long-term follow-up after operation. The advantages of endoscopic rhinoplasty in the treatment of inverted papilloma are well known. The main disadvantage is that it is difficult to perform mass resection, but mass resection is not the key to the treatment of nasal inverted papilloma. The most important principle of surgical resection is to completely remove the tumor to reach the bone, and partially remove the bone at the base of the tumor with an electric drill. The application of nasal endoscope technology, imaging technology and electric cutter makes it possible to treat inverted papilloma of nasal cavity and paranasal sinuses under nasal endoscope. The key to successful operation is to locate the tumor attachment point and tumor range. According to the different attachment points of inverted papilloma, the operation of inverted papilloma can be divided into local small-scale resection, total sphenoid screen resection, external wall (enlarged) resection under nasal endoscope, DRAF II-III operation and combined operation under nasal endoscope. Postoperative patients should be followed up by nasal endoscope every 3~6 months.