Transnasal Approach Research Articles

A Rare Case of Clival Hemangioma Simulating Chordoma

AbstractPrimary intraosseous hemangiomas are rare, benign, vascular malformations that account for ∼1% of all primary bone neoplasias. A 59-year-old female patient with unknown comorbidities had a history of headache, visual impairment and dizziness that led to the diagnosis of a clivus tumor. Two resections were attempted through transcranial and transnasal transsphenoidal approach in the last two years in another hospital. The initial MRI scan showed an expansive lesion with T2 hyperintense signal and diffuse, heterogenic contrast enhancement. Clival chordoma was the main diagnostic hypothesis done. A CT scan was performed to evaluate the extent of clival invasion, the sinus anatomy, and the clival destruction - all simulating clival chordoma. The interdisciplinary tumor board decided to proceed with endoscopic endonasal tumor resection. There were no postoperative complications and the histopathological analysis revealed a primary intraosseous haemangioma. Skull base intraosseous hemangiomas are rare entities, with a limited number of case reports found after literature reviews, especially in the clival region. The clinical pattern and imaging characteristics can vary widely according to the tumor extension and development, simulating some other common tumors found at this topography. We present a case report of a clival intraosseous hemangioma presenting as an isolated abducens paresis with a positive outcome after intranasal endoscopic resection after two years of follow-up.

Flexible in-cavity MRI receiving coil for ultra-high-resolution imaging of the pituitary gland.

The objective of this study was the preclinical design and construction of a flexible intrasphenoid coil aiming for submillimeter resolution of the human pituitary gland. Sphenoid sinus measurements determined coil design constraints for use in > 95% of adult patients. Temperature safety parameters were tested. The 2-cm-diameter coil prototype was positioned in the sphenoid sinus of cadaveric human heads utilizing the transnasal endoscopic approach that is used clinically. Signal-to-noise ratio (SNR) was estimated for the transnasal coil prototype compared with a standard clinical head coil. One cadaveric pituitary gland was explanted and histologically examined for correlation to the imaging findings. With the coil positioned directly atop the sella turcica at a 0° angle of the B0 static field, the craniocaudal distance (21.2 ± 0.8 mm) was the limiting constraint. Phantom experiments showed no detectable change in temperature at two sites over 15 minutes. The flexible coil was placed transnasally in cadaveric specimens using an endoscopic approach. The image quality was subjectively superior at higher spatial resolutions relative to that with the commercial 20-channel head coil. An average 17-fold increase in the SNR was achieved within the pituitary gland. Subtle findings visualized only with the transnasal coil had potential pathological correlation with immunohistochemical findings. A transnasal radiofrequency coil feasibly provides a 17-fold boost in the SNR at 3 T. The ability to safely improve the quality of pituitary imaging may be helpful in the identification and subsequent resection of small functional pituitary lesions.

Chondrosarcoma of the Nasal Cavity and Paranasal Sinuses: A Rare Entity.

Background: Chondrosarcomas are slow-growing malignant tumors that originate in cartilaginous structures. They typically manifest in the head and neck region, with a preference for the maxillofacial skeleton, particularly the mandible and maxilla. However, chondrosarcoma of the sinonasal tract is exceptionally rare, and only few cases have been reported. Case Presentation: This report details the case of a 43-year-old woman who incidentally discovered chondrosarcoma in the maxillary and ethmoid sinuses with nasal extension. Subsequently, the patient underwent surgery via a paralatero-nasal approach with adjuvant radiotherapy. The aim of this study was to describe the clinical findings, management, and outcome of sinonasal tract chondrosarcoma. Conclusions: The primary treatment for chondrosarcomas remains surgery, with a transnasal endoscopic approach offering a viable option for complete resection in select cases.

Adjunctive transseptal corridor: Technique for endoscopic resection of orbital tumor.

The transnasal endoscopic approach is increasingly used for resection of tumors that are located inferiorly and medially within the orbit. However, this usually requires multiple-handed manipulations, which demand a second corridor for an assistant. Here, we introduce a simple transseptal corridor from the contra-nare, to facilitate assistant instrument maneuverability. This simple, minimally invasive skill greatly improves operation efficiency and deserves greater attention in endoscopic orbital surgery.

Ethmoid Osteoblastoma: A Case Report and Pooled Analysis of Cases.

Osteoblastoma is a typically noncancerous bone tumor commonly found in the spine and long bones of the arms and legs. It is exceedingly rare for this tumor to occur in the paranasal sinuses. We present a case of osteoblastoma in a 13-year-old boy affecting the ethmoid sinus, which manifested as exophthalmos. A computed tomography scan revealed an expansive lesion in the right ethmoid sinus, causing compression and displacement of the orbital contents to the right. The lesion exhibited a mix of ground glass opacity and dense bone. On magnetic resonance imaging, the less dense areas of the tumor showed strong enhancement, while the densely sclerotic regions appeared as signal voids on all imaging sequences. A combined transorbital and transnasal approach was performed to remove the tumor. Histologically, the tumor consisted expansile growth surrounded by a sclerotic rim of inter-anastomosing trabeculae of woven bone set within loose edematous fibrovascular stroma. This case highlights the unusual occurrence of osteoblastoma in the ethmoid sinus, a location seldom associated with this type of tumor, and adds to the existing literature on this topic and offers a new surgical approach to managing this entity.

Contralateral Transmaxillary Corridor Used in Endoscopic Endonasal Approach for Resecting Adenoma Invading the Retrocarotid Area of the Cavernous Sinus and Beyond: Surgical Anatomy, Patient Selection Algorithm, and Illustrative Cases.

The cavernous internal carotid artery (cICA) and its branches can make it challenging to approach the lateral portion of the retrocarotid area of the cavernous sinus (RcACS) and surrounding areas during the endoscopic endonasal approach (EEA). This can sometimes require more invasive transcranial approaches, causing a higher risk of complications. We sought to explore the feasibility of adding a contralateral transmaxillary (CTM) corridor to improve access to the RcACS during EEA. We performed EEA and CTM extensions on 6 cadavers (12 sides) using image guidance. The depth of the surgical corridor, the surgical exposure, the angle of attack, and the trajectory to the anterior genu of the cICA were measured. Two illustrative clinical cases are presented. Compared with the contralateral transnasal approach, the CTM corridor provided a 10.76 (5.32)-mm shorter distance ( P < .001), 36.23% (20.70%) larger surgical exposure ( P < .001), and a 24.6° (3.4°) more parallel trajectory to the anterior genu of the cICA ( P < .001). The mean angle of the lateral nasal wall line and the middle eye line was equal to the mean angle of the contralateral transnasal ( P = .075) and CTM ( P = .262) approaches, respectively. The CTM corridor allowed us to achieve near-total resection of the RcACS and beyond in 2 invasive adenomas with significant lateral extension. The CTM corridor is a feasible addition to standard EEA to access the RcACS and beyond, providing a more medial-to-lateral trajectory and improved access. The middle eye line can be used as a reference to help select patients for this approach.

Morphometric Variations of Sphenoidal Air Sinuses in Human Cadavers

Background: The sphenoid sinuses are difficult to approach directly, so a transnasal approach is preferred. Due to the variable extent of pneumatization, there are variations in the size and shape of sphenoid ostium. These sinuses are related to many important structures, and they produce surface impressions on sinus walls. There are very few cadaveric studies that describe sphenoid sinuses morphometrically and their relation to nearby important structures. Hence, this study was undertaken to study the morphological variations of sphenoid sinuses; to measure the dimensions of the sphenoid sinuses; to classify the sphenoid sinuses and to study the variations of relation of important structures along the walls of the sphenoid sinuses. Methodology: The present study was performed on 25 formalin-fixed cadavers (50 hemisections). The morphometric anatomy of the sphenoid sinuses was studied by taking midline sagittal sections of the head, neck, and face regions in cadavers. Anteroposterior depth (infrasellar) and vertical height (presellar) of the sinus were measured. Based on the morphology of the sinus, they were grouped into conchal, presellar, sellar, and postsellar types. Surface impressions made by the carotid artery and optic nerve on the lateral wall of the sinus were observed. Results: The most common type of sphenoid sinuses was the sellar variety (68%), with conchal being the least common (0%). Most of the sinuses (88%) were divided by the intersinus septa. A round-shaped ostium of the sphenoid air sinus was found to be common (56%). Impressions of the internal carotid artery and optic nerve into the lateral wall of the sinus were prominent in highly pneumatized sphenoid sinuses. Conclusions: Variations observed are mainly due to variable pneumatization of the sphenoid bone. The degree of pneumatization will result in protrusion of the surrounding structures such as internal carotid artery and optic nerve into the sinus wall. The extent of pneumatization will determine the degree of protrusion of surrounding structures.

Gross-total resection in optic nerve sheath meningiomas: minimally invasive and cosmetic pleasing

PurposeThe optic nerve sheath meningioma (ONSM) is one of the most challenging tumors in orbital surgery. From the perspective of mental health and patient needs, we analyzed the necessity and importance of the endoscopic transnasal approach (ETA) combined with optic nerve transection (ONT) in gross-total resection (GTR) in ONSM patients with residual vision and aim to broaden the use of ONT for specific people.MethodsThe authors included patients with ONSMs who were treated between 2014 and 2022. We divided those cases into two groups named ETA group and lateral orbitotomy approach (LOA) group. We present the application of ETA and analyze the preoperative indication of the ONT and compared the advantages and disadvantages between ETA and LOA. The degree of tumor resection was based on imaging and surgical evaluation.ResultsA total of 23 patients with ONSM were included. Sixteen patients underwent ETA, and seven underwent LOA. Among ETA cases, GTR was achieved in 14 patients with ONT and most patients maintained normal eye movement function (75%) and morphology (93.75%). In the ETA group, 14 patients experienced vision loss, while two other patients saw improvements in vision. And proptosis was alleviated (5.20 ± 2.34 vs 0.27 ± 0.46, p < 0.0001). Six patients with blindness and proptosis of the LOA group resulted in GTR with ONT and ophthalmectomy. Although intracranial extension and recurrence included no cases in the two groups, a significant psychological gap was presented due to cosmetic problems.ConclusionsUnder the premise of reducing damage and improving aesthetics, the selection of ETA combined with ONT to gross-total resect ONSMs successfully provides a minimally invasive access with acceptable complications. As an important adjunct to GTR in the surgical treatment of ONSM, the scope of ONT application should be expanded to relieve the patient’s psychological burden.

The value of cryoablation in orbital surgery.

Aim of this article is to give an overview of the technical background and the advantages of modern devices for different applications of cryoablation in cranio-orbital neurosurgery.The treatment of orbital lesions is complicated by the complex and potentially inapparent anatomy due to retro-orbital fat. With the help of cryoprobes different well-defined lesions such as cavernous venous malformations can be safely and effectively removed thanks to the cryoadhesive effect. Their use has been described in several different approaches including traditional lateral or transcranial orbitotomy but also anterior transconjunctival as well as transnasal endoscopic approaches. Recently, single-use devices were introduced that allow the use of cryosurgery also without the need for large investment or service costs.

Endoscopic endonasal approach for skull base chordoma

BackgroundChordoma is a rare slow-growing malignant bone tumor that arises from embryonic notochordal remnants in the axial skeleton. Clival chordomas have a high propensity for extension through the skull base and a high proclivity for recurrence. Recently, resection of skull base chordomas through the endoscopic transnasal approach has become the standard way of managing these lesions with the new advancements in neuronavigation and reconstructive techniques in skull base surgery.MethodsIt is a retrospective study of all patients with clival chordoma that were operated upon using endoscopic endonasal resection at the Main Alexandria University Hospital during the period from March 2008 to April 2013. The extent of surgical resection was assessed intraoperatively and confirmed by the postoperative MRI study performed 8–12 weeks, 6 months, and yearly after the surgery.ResultsTwelve patients with clival chordoma were managed by endoscopic transnasal resection. Gross total resection confirmed by postoperative MRI was achieved in four cases, subtotal resection in six cases, and partial resection in two cases of clival chordoma. In cases where gross total resection was not achieved, residual tumors were adherent to vital neurovascular structures as confirmed with the utilization of an intraoperative imaging navigation device. A study of postoperative complications and possible recurrence was done for all cases.ConclusionsThe findings of this study highlight the significance of gross total resection as a major determinant for preventing the recurrence of chordoma. Our findings also support the validity of the endoscopic approach for the management of clival chordoma especially when the approach is tailored based on the site and extent of the tumor.

Choanal atresia repair in Germany : Resection of dorsal septal parts and stents in focus

Various surgical techniques using transpalatinal, transseptal, and transnasal approaches for surgical repair of choanal atresia have been developed over the past 200years. Endoscopic endonasal surgery with resection of dorsal septal parts and without the use of stents is the current scientific trend, as high success rates with low complication rates can be achieved. This study examined whether this technique has actually become standard in Germany, and also investigates the role played by stents. Atotal of 52ear, nose, and throat (ENT) hospitals in Germany, including all 39university ENT hospitals and 13non-university maximum-care ENT hospitals, were asked which surgical technique they use for choanal atresia repair and whether stents are used. For dorsal septal resection, 39of 44responding hospitals (89%) indicated that they resect dorsal septal parts, 85% of the university hospitals and 100% of the non-university hospitals. For use of stents, 20of 48responding hospitals (42%) reported not using stents, whereas 39% of the university hospitals and 50% of the non-university hospitals do use them. Endoscopic endonasal choanal atresia repair with resection of dorsal septal parts is, in most instances, used as the standard technique in large ENT hospitals in Germany. Routine use of stents is still widespread. The future aim should be to reduce the use of stents in the treatment of choanal atresia and to use this method only in difficult, individual cases.

The efficacy and safety analysis of endoscopic resection for infratemporal fossa benign mass

Objective: To investigate the efficacy and safety of endoscopic resection of infratemporal fossa mass and to determine the indications for surgery. Methods: A retrospective case series study was conducted, including a total of 29 patients who underwent endoscopic surgery to treat infratemporal fossa mass in the Department of Rhinology of Beijing Tongren Hospital, Capital Medical University, from April 2008 to December 2021. Ten males and 19 females were included in the study, with age of (46.5±13.7) years. Pre-and post-operative sinus CT, sinus or nasopharyngeal enhanced MRI were evaluated, respectively. The main outcome measurements were the total resection of mass and the incidence of surgery-related complications. Results: Among the 29 cases of infratemporal fossa mass, 22 were schwannomas, 3 were cysts, 2 were neurofibromas, 1 was pleomorphic adenoma and 1 was basal cell adenoma. Preoperative imaging showed well-defined lesion boundaries, and postoperative pathology confirmed the benign nature of all cases. The endoscopic transnasal approach was used in 28 patients, while the combination of the transnasal approach and the transoral approach was used in 1 patient. Complete tumor removal was achieved in all cases with a 100% resection rate. The average follow-up time was 38 months (7-168 months), and no tumor recurrence was observed. Conclusions: The Endoscopic transnasal approach is a safe and effective surgical approach for the treatment of benign tumors or masses in the infratemporal fossa.

Congenital basal encephaloceles involving functionally important structures

We reviewed 43 articles (78 cases) devoted to basal encephaloceles involving functionally important structures. Analysis included transsphenoidal and sphenoethmoidal hernias. Nasal breathing disorders were found in 76.9% of cases, decreased visual acuity - 53.8%, endocrine disorders - 44.9%, nasal CSF leakage - 14.1%, meningitis - 10.3%. Concomitant malformations occurred in 85.9%. Severe respiratory disorders (52.6%, p<0.05) and multiple concomitant malformations (71.7%, p<0.05) were more common among patients with sphenoethmoidal encephalocele. Among 78 patients, 73.1% underwent surgery while follow-up was preferable in 26.9% of cases. There was progression of endocrine disorders (9.5%), visual impairment (4.8%) and nasal breathing disorders (4.8%) in follow-up period. Surgical treatment also has many risks. Transcranial, transnasal, transoral and combined approaches are currently used. It was not possible to establish the most effective surgical approach due to heterogeneous clinical data. Postoperative complications occurred in 47.4% of cases (endocrine disorders - 33.3%, CSF leakage - 8.8%, visual impairment - 1.8%, infectious complications - 14%). Mortality rate was 3.5%. Congenital basal encephalocele involving functionally important structures is an extremely rare developmental defect. Such patients often have concomitant anomalies. Comprehensive examination is necessary to estimate the structures included in hernial sac and concomitant diseases. Treatment strategy should be determined individually after thorough examination and comparison of all risks. Surgical treatment is associated with high risk of complications due to damage to the structures comprising encephalocele.

A Giant Frontoethmoidal Sinus Osteoma Presenting With Frequent Sleep Apnea Attacks: A Case Report

Background: Paranasal sinus osteomas are benign, slow-growing tumors that are typically asymptomatic. However, in rare cases, these tumors can grow to a giant size and extend into neighboring structures such as the brain, orbit, or nasal cavity, leading to clinical symptoms. These symptoms may include chronic headaches, rhinorrhea, neurological deficits, and visual impairment. Case presentation: Here, we present the case of a 27-year-old male patient who presented to our hospital with chronic headaches and frequent sleep apnea. Upon rhinoscopic examination, mucosal polyposis was observed. Further evaluation through computed tomography revealed a giant fibroosseous tumor in the frontal sinus, which exhibited aggressive extension into the brain parenchyma. Contrast-enhanced magnetic resonance imaging confirmed the presence of a giant tumor with an 8 cm diameter, exerting a mass effect on the underlying brain tissue. To address this complex case, the patient underwent a combined transcranial and transnasal surgical approach. Following the surgery, the patient experienced significant improvement in his symptoms. Conclusions: This report highlights a rare case of sleep apnea secondary to a giant frontoethmoidal osteoma with intracranial extension. The presence of frontal sinus osteomas can lead to serious clinical consequences. Timely diagnosis and intervention are crucial to prevent intracranial extension and mitigate potential complications associated with these lesions.

Endoscopic Transnasal Approach for Microprolactinomas with Experience of 125 Cases in a Single Center

Endoscopic Transnasal Approach for Microprolactinomas with Experience of 125 Cases in a Single Center

Endoscopic transnasal resection of clival meningiomas

Surgical treatment of ventral and ventrolateral meningiomas of posterior cranial fossa is difficult in modern neurosurgery. This is due to peculiarities of approach to these areas and concentration of critical structures (cranial nerves and great vessels). Currently, endoscopic transnasal approach to these meningiomas allows partial, and in some cases, total resection. However, this technique is not widespread. To analyze the world literature data on postoperative outcomes in patients with clival and petroclival meningiomas after endoscopic transnasal resection. We analyzed 22 articles representing treatment of 61 patients with clival and petroclival meningiomas. Total or near-total resection was achieved in 22.9% of cases, subtotal resection - 40.9%, partial resection - 26.2% (data were not provided in other cases). Even partial and subtotal resection leads to significant regression of symptoms. Endoscopic transnasal surgery is a full-fledged alternative to transcranial approaches in surgical treatment of clival meningiomas. It is also an additional option for patients with petroclival meningiomas after ineffective transcranial approaches. Transnasal tumor shrinkage and devascularization lead to brainstem decompression, regression of hydrocephalus and baseline clinical symptoms.

The biportal transorbital approach: quantitative comparison of the anterior subfrontal craniotomy, bilateral transorbital endoscopic, and microscopic approaches.

The aim of this study was to assess the surgical use and applicability of a biportal bitransorbital approach. Single-portal transorbital and combined transorbital transnasal approaches have been used in clinical practice, but no study has assessed the surgical use and applicability of a biportal bitransorbital approach. Ten cadaver specimens underwent midline anterior subfrontal (ASub), bilateral transorbital microsurgery (bTMS), and bilateral transorbital neuroendoscopic surgery (bTONES) approaches. Morphometric analyses included the length of the bilateral cranial nerves I and II, the optic tract, and A1; the area of exposure of the anterior cranial fossa floor; craniocaudal and mediolateral angles of attack (AOAs); and volume of surgical freedom (VSF; maximal available working volume for a specific surgical corridor and surgical target structure normalized to a height of 10 mm) of the bilateral paraclinoid internal carotid arteries (ICAs), bilateral terminal ICAs, and anterior communicating artery (ACoA). Analyses were conducted to determine whether the biportal approach was associated with greater instrument freedom. The bTMS and bTONES approaches provided limited access to the bilateral A1 segments and the ACoA, which were inaccessible in 30% (bTMS) and 60% (bTONES) of exposures. The average total frontal lobe area of exposure (AOE) was 1648.4 mm2 (range 1516.6-1958.8 mm2) for ASub, 1658.9 mm2 (1274.6-1988.2 mm2) for bTMS, and 1914.9 mm2 (1834.2-2014.2 mm2) for bTONES exposures, with no statistically significant superiority between any of the 3 approaches (p = 0.28). The bTMS and bTONES approaches were significantly associated with decreases of 8.7 mm3 normalized volume (p = 0.005) and 14.3 mm3 normalized volume (p < 0.001) for VSF of the right paraclinoid ICA compared with the ASub approach. No statistically significant difference in surgical freedom was noted between all 3 approaches when targeting the bilateral terminal ICA. The bTONES approach was significantly associated with a decrease of 105% in the (log) VSF of the ACoA compared with the ASub (p = 0.009). Although the biportal approach is intended to improve maneuverability within these minimally invasive approaches, these results illustrate the pertinent issue of surgical corridor crowding and the importance of surgical trajectory planning. A biportal transorbital approach provides improved visualization but does not improve surgical freedom. Furthermore, although it affords impressive anterior cranial fossa AOE, it is unsuitable for addressing midline lesions because the preserved orbital rim restricts lateral movement. Further comparative studies will elucidate whether a combined transorbital transnasal route is preferable to minimize skull base destruction and maximize instrument access.

Multifocal Giant Cell Tumor of the Nasal Fossa: Case Report and Literature Review.

Giant cell tumors of bone (GCT) are rare soft tissue tumors, that account for 3%-5% of primary bone tumors with <2% occurring in the head and neck. The nasal cavity is a highly unusual site of presentation. We reviewed 15 cases of GCT of nasal cavity and paranasal sinuses. We add 1 case to the literature. The case herein reported, appears to be the second nasal fossa GCT described in the literature and the first documented case with multifocal localization. A case of multifocal GCT of the nasal cavity is described. Although rare in the general population, GCT should be included among the possibilities in the differential diagnosis when evaluating tumors of the head and neck. Management of this particular tumor remains challenging; surgical removal is still the gold standard treatment, preferring a minimally invasive trans-nasal approach to reduce intra and post-operative morbidity. Laryngoscope, 134:2774-2778, 2024.

A Case of Sellar Arachnoid Cyst Operated Using the Endoscopic Supraorbital Keyhole Approach

BACKGROUND AND IMPORTANCE: In recent years, sellar arachnoid cysts (ACs) have been increasingly treated using an endoscopic transnasal approach. It is important to connect the subarachnoid space with the AC to prevent recurrence; however, a high frequency of postoperative cerebrospinal fluid (CSF) leakage has been reported with the endoscopic transnasal approach, and the suitability of the endoscopic transnasal approach for treating sellar ACs is questionable to begin with. CLINICAL PRESENTATION: A man in his 40s underwent surgery for a sellar AC compressing the optic chiasm. The normal pituitary gland was compressed dorsally by the cyst, and an endoscopic supraorbital keyhole approach was adopted to reduce the risk of postoperative CSF leakage. A small incision was made in the right eyebrow, and a small craniotomy was performed. A rigid scope was used to approach the cyst and incise the arachnoid membrane of the prechiasmatic cistern and the anterior wall of the cyst. Postoperatively, the cyst shrank, and the preoperative visual field defects improved. The duration of the endoscopic manipulation was approximately 40 minutes. DISCUSSION: The endoscopic supraorbital keyhole approach eliminates the need to incise the dura mater of the anterior skull base and reduces the risk of CSF leakage compared with the transnasal approach. In addition, cumbersome dural reconstruction using fat and fascia is not required during the supraorbital keyhole approach, which reduces operation time. CONCLUSION: The endoscopic supraorbital keyhole approach may be more suitable than the transnasal approach for surgery of sellar ACs.

Nasal Endoscopic Incision and Drainage Transnasal Retropterygoid Approach to Upper Parapharyngeal Abscess: A Novel Technique.

Parapharyngeal infection is a well-known disease of otorhinolaryngologists. Rapid onset, short duration, severe symptoms, and manifestations such as sore throat and dysphagia are common characteristics treated primarily by surgical incision and drainage. Traditional surgical approaches encompass endoscopic transoral/nasal, transparotid, transcervical, or a combination thereof. We report a novel technique of nasal endoscopic incision and drainage transnasal retropterygoid approach to an upper parapharyngeal abscess. This report presents a case of a 14-year-old man presented with severe right neck and head pain, who was found to have an upper parapharyngeal abscess during a nasal endoscopic parapharyngeal exploration via a retropterygoid approach. The intraoperative frozen section revealed chronic mucosal inflammation and mild to moderate dysplasia of the squamous epithelium, but no carcinoma.