Melanotic Neuroectodermal Tumor Research Articles

Operative Technique for Extirpation of Large Melanotic Neuroectodermal Tumor of Infancy Involving Alveolus and Anterior Maxilla in the Region of the Premaxilla.

Melanotic neuroectodermal tumors of infancy are rare, benign neoplasms predominantly affecting the craniofacial region, and they are typically managed through resection with minimal need for reconstruction. However, in exceptional cases, larger or more complex tumors may necessitate open craniofacial approaches, with limited literature detailing the surgical strategies for these scenarios. The authors report a distinctive case of an aggressively expanding melanotic neuroectodermal tumor of infancy in a pediatric patient, describing their approach for the tumor's resection. A 10-week-old male presented to the hospital with a reported 2 weeks of swelling of the left upper gum line noted by his mother and pediatrician. Preoperative biopsy revealed a soft, fluid-filled lesion, prompting surgical planning for complete excision. Intraoperative assessment with a nasal speculum by ENT, and utilization of a piezoelectric saw by plastic surgery facilitated precise tumor resection. The surgical technique required meticulous dissection, ensuring clear margins while preserving surrounding structures. The tumor, encompassing the alveolus and anterior maxilla, was completely excised with negative margins. Utilization of the piezoelectric saw facilitated safe bone cutting, preserving vital structures while ensuring comprehensive tumor removal. The patient tolerated the procedure well, with no immediate postoperative complications. Complete resection is essential in minimizing the risk of recurrence in MNTI. The utilization of piezoelectric surgery enhances precision and safety in tumor resection, preserving anatomic integrity and optimizing patient outcomes. This case underscores the importance of meticulous surgical techniques in managing craniofacial tumors, advocating for the adoption of advanced surgical tools to improve clinical outcomes.

HGG-09. CONTRASTING CLINICAL COURSES OF THREE PEDIATRIC PATIENTS WITH PDGFRA AMPLIFIED RADIATION-INDUCED HIGH-GRADE GLIOMA

Abstract BACKGROUND Radiation-induced gliomas (RIG) can occur in 3% of patients receiving cranial radiation. Often, these gliomas are high-grade, treatment refractory, and share common molecular profiles like PDGFRA amplification, regardless of their previous malignant origin. Despite similar genetic alterations, the clinical course of these tumors is varied and not well-studied. Herein, we describe three patients with a PDGRFA-amplified RIG with a particular focus on their contrasting disease course. CASE DESCRIPTION: Our first patient is a now-deceased male diagnosed with medulloblastoma at 5 years of age, treated with surgical resection and craniospinal radiation followed by chemotherapy per COG ACNS0332. Ten years later, he was diagnosed with diffuse pediatric type high-grade-glioma (HGG) in the pons with PDGFA, KIT, MTAP amplification, and CDKN2A/B loss. His condition deteriorated quickly, and he succumbed to his disease in 8 weeks after family decided against further therapies. Our second patient is a now 20-year-old female, initially diagnosed with a craniopharyngioma at 6 years of age and treated with surgical resection and adjuvant radiation therapy. Eleven years later, she developed a diffuse pediatric type HGG in the pons with PDGFRA, MDM2, and MYCN amplification. She was treated with radiation therapy and has had stable disease on serial imaging for 3 years. Our third patient is a now-deceased male diagnosed with a right temporal melanotic neuroectodermal tumor at 5 years of age, treated with surgical resection and craniospinal radiation followed by chemotherapy per POG99701. Fifteen years later, he developed a diffuse pediatric-type HGG in the cerebellum/pons with PDGRFA amplification. He was treated with proton radiation and concurrent oral Temozolomide per COG ACNS0423. His disease progressed on treatment, and he died prior to initiation of a PDGFRA kinase inhibitor (avapritinib). CONCLUSIONS Further investigation into the underlying factors that drive the differing disease course in patients with RIG is needed.

Focus on melanotic neuroectodermal tumor of infancy

Melanotic neuroectodermal tumor of infancy (MNTI) is a very rare benign neoplasm of probable neurocristic origin. It primarily affects children in the first year of life, with the median age at diagnosis of 4.5 months (range 0–804 months). It usually presents as a fast-growing, painless tumor developing within maxilla, skull bones or mandible but other locations are also possible, especially in older children. The cornerstone of treatment of MNTI is surgery, however local relapses after incomplete tumor excision are common, particularly in patients younger than 2 months of age. Rare cases of multiple recurrent, inoperable or metastatic MNTI pose therapeutic challenges. In such clinical scenarios, various regimens of neoadjuvant chemotherapy based on schemes for neuroblastoma or Ewing sarcoma have been used with partial regressions in some patients, enabling less mutilating delayed surgery. The use of radiotherapy is limited due to very young age of patients with MNTI. No targeted therapies have been found useful so far. Long-term prognosis of localized MNTI is favorable. However, extensive or recurrent lesions can result in functional or esthetic sequelae after surgical removal. Rare cases of malignant/metastatic tumors and MNTI diagnosed in older children have unfavorable outcomes. Further collaborative studies to establish standards of management in patients with MNTI are necessary to improve outcomes and diminish sequelae of surgery. This article presents a literature review on this very rare tumor entity, re-evaluated in the light of the experience gained in the national working groups joined together within the European Cooperative Study Group in Pediatric Rare Tumors (EXPeRT).

Melanotic Neuroectodermal Tumor of Infancy: A Case Series and Comprehensive Review of this Rare Pediatric Neoplasm

Melanotic Neuroectodermal Tumor of Infancy: A Case Series and Comprehensive Review of this Rare Pediatric Neoplasm

Melanotic Neuroectodermal Tumor of Infancy: A Case Report and Literature Review

Melanotic neuroectodermal tumor of infancy (MNTI), first described almost a century back, is of neural crest origin, locally aggressive, a rare biphasic neoplasm of infancy with a slightly higher male preponderance. In the last 100 years since the first description of MNTI, only around 500 cases have been described from 32 countries. We present a 7-month-old female child with 3 × 2 cm hard swelling in the oral cavity and right-side facial region for 3 months. Contrast-enhanced computed tomography scan and contrast-enhanced magnetic resonance imaging scan revealed a hypodense lesion of size 2.5 × 2 × 1.6 cm with relatively well-corticated walls. The lesion appeared to arise from the right maxillary alveolus with erosion of the floor of the maxillary sinus. A 7 × 5 mm tooth was visualized within the lesion. There was minimal enhancement in the postcontrast study. With the following provisional diagnoses—odontogenic keratocyst, dentigerous cyst, and unicystic ameloblastoma—the child underwent excision of the lesion. Intraoperatively, Hopkin's rigid endoscope 4 mm was used to ensure complete tumor removal in the maxillary sinus. Histopathological and immunohistochemistry examination resulted in the diagnosis of MNTI. On 1-year follow-up, the child did not show any signs of recurrence. A high index of suspicion, early diagnosis, and timely treatment are needed to diagnose such a rare tumor, to avoid morbidity, and to plan effective management when an infant presents with facial swelling. It should be complemented with close follow-up to identify recurrence early. Use of endoscope whenever feasible is encouraged by the authors to ensure adequate tumor removal.

Melanotic Neuroectodermal Tumor of Infancy: A Case Report with Review of Literature

AbstractMelanotic neuroectodermal tumors of infancy are rare pigmented neuroectodermal locally aggressive tumors that usually occur within 1 year of life. Head and neck areas are frequently involved with maxilla being the most common site. Expansile growth and high recurrence rate are characteristics of this cancer. Though rare, radiologists and clinicians must be aware and should consider this entity when diagnosing pediatric head and neck masses. Computed tomography can be used for diagnosing and looking at the extent of the disease and predicting the operative outcome. Surgery with wide resection margin is the mainstay of treatment for these masses. Surgery followed by adjuvant chemotherapy and radiation is reserved for aggressive malignant lesions. Since it has a high recurrence rate, follow-up is done with imaging and clinical examination. Early detection and treatment of recurrence have a favorable outcome for the patients.

Long term follow-up results of enucleation as the definitive treatment for melanocytic neuroectodermal tumour of infancy and a review on its treatment.

Melanotic Neuroectodermal tumour of Infancy (MNTI) is a rare entity of pigmented neoplasms of head and neck region. It predominantly occurs within the first year of life. The authors present enucleation as the definitive surgical treatment, with reference to the five departmental cases of MNTI with no recurrence at 5years and 1year of follow-up of other 4 cases. Five cases of MNTI (age group of 2.5months-7 months) presented to our department as a large bluish-brown non tender swelling protruding into the oral cavity. Radiologic imaging revealed a well-circumscribed solid-cystic enhancing lesion causing elevation of orbit and nasal obliteration in maxillary region and causing buccolingual expansion in mandible. The tumor was enucleated without any bony margin. Histopathological and immunohistochemical evaluation (EMA, Pan Cytokeratin, HMB45, S100, p53, ki67) were done. Patients were followed up at regular intervals and had no recurrence at mean 3years follow-up. A detailed mention of surgical pearls, differential diagnosis and a brief literature review are also done. MNTI is a pigmented neoplasm that occurs in infants and in head and neck region mostly involves the upper alveolus and maxilla, followed by skull and mandible. Incisional biopsy is needed to confirm the tumour and rule out other malignant round cell tumours. Enucleation of the lesion is necessary without the need for any extra bony margin removal. Close long term follow up is necessary. Conservative surgical approach is usually the best first choice for MNTI treatment.

Melanotic Neuroectodermal Tumour of Infancy.

Melanotic neuroectodermal tumour of infancy (MNTI) is a locally aggressive neoplasm of neural crest origin. It is primarily a paediatric tumour, and 95% of the cases occur in children below 1 year. The tumour mainly affects the head and neck region. It shows a predilection for the craniofacial sites and the most common site affected is anterior maxilla. Microscopically, it is characterized by a biphasic population of neuroblastic cells and pigmented epithelial cells. Although generally considered as a benign tumour, it can invade the adjacent muscle and bone, causing destruction of the involved site. The rapidity in growth and the aggressive clinical behaviour of the tumour can be deceptive and hence lack of familiarity with the clinical characteristics of the tumour may often lead to an erroneous diagnosis of malignancy. The treatment of choice for MNTI is excision, and it is usually curative. Extensive surgery in a child may interfere with the normal growth and development of the facial structures and reconstruction can be very challenging in infants. Hence, early diagnosis is critical for the effective management. Clinical findings, histopathological features, and differential diagnosis of a classic case of melanotic neuroectodermal tumour of infancy are discussed.

Melanotic neuroectodermal tumor of infancy presenting as rapidly enlarging cheek mass

Malignancies in infants are unusual and often difficult to diagnose. We discuss the presentation, diagnosis, and treatment of a patient with a melanotic neuroectodermal tumor of infancy (MNTI) and discuss the limited literature of this topic.

Clinical and imaging features of melanotic neuro-ectodermal tumor of infancy of the maxillary bone: report of four cases and review of the literature

Melanotic neuro-ectodermal tumor of infancy (MNTI) is an extremely rare tumor. The purpose of this study was to describe the imaging features of maxillary bone MNTIs and introduce the key points for clinical diagnosis of MNTI. We retrospectively reviewed four patients with histology-proven MNTIs arising from the maxillary bone. All patients underwent ultrasonic inspections, CT and/or MR scanning. Combined with previously literature, the imaging features were comprehensively evaluated and analyzed. All MNTIs showed a firm, non-ulcerated rapidly-growing soft-tissue swelling with pigmented (blue-colored or black-colored or gray-colored) mucosa. The onset ages were younger than 6 month-old. CT images showed osteolytic or expansive bone destruction of the involved maxillae, fragmentary cortical bone, “free-floating” tooth germs, with or without spiculated/sunburst periosteal reaction. The tumor appeared lightly hyper-intense on T2-weighted sequences, while isointense or lightly hypo-intense or lightly hyper-intense signal on T1-weighted sequences. Enhanced images all displayed heterogeneous enhancement. No metastasis features of lymph nodes or abdominal organs were demonstrated by cervical and abdominal ultrasonic inspections. As a conclusion, accurate recognition of the imaging features of MNTI combined with history and clinical manifestations (early infancy, painless, firm, pigmented mucosa, non-ulcerating lesion) can provide clues for diagnosis of this rare entity.

Melanotic neuroectodermal tumor of infancy: Case report and literature review.

Melanotic neuroectodermal tumor of infancy (MNTI) is a rare benign tumor. Here, we report the diagnosis and treatment of 1 case of MNTI in the maxilla and discuss its clinical and pathological features, imaging features, treatment, and prognosis.

LINC-03. A single center retrospective analysis of current therapy and outcome of central nervous system tumors in children of Beijing

OBJECTIVE: To explore the clinical characteristics, therapy and outcome in children with central nervous system (CNS) tumors in Beijing, China. METHODS: Clinical data of 1003 patients with newly diagnosed CNS tumors under the age of 15 years admitted to Beijing Shijitan Hospital between January 2017 and December 2021 were retrospectively analyzed. The diagnoses were confirmed by pathology and/or molecular tests. RESULTS: 34 patients were lost to follow up. Medulloblastoma (n=472), ependymoma (n=79), ETMR (n=59) and pinealoblastoma (n=19) were treated according to HIT-2000/2017, 5-year progression-free survival (PFS) and overall survival (OS) were 76.4 ± 2.3%/ 84.8 ±1.9% in MB, 88.8±3.7% /89.5±3.8% in ependymoma, 49.9±7.6%/59.6±10.7% in ETMR, and 3y-PFS/OS of 11.1±10.5%, 90.0±9.5% in pinealoblastoma. The detailed histology of 59 cases of embryonal tumors included 40 cases of CNS embryonal tumor, 9 neuroblastoma, 7 ETMR, and 3 rare tumors (Intracranial mesenchymal tumor with FET-CREB fusion, CNS high-grade neuroepithelial tumor with BCOR alteration, and Melanotic neuroectodermal tumor of infancy). Among 19 cases of pinealoblastoma, two contain DICER1 mutations. Atypical teratoid/rhabdoid tumors (n=36) were treated by EU-RHAB-Protocol with 3y-PFS/OS of 42.2 ± 9.4 % and 62.8 ± 9.5 %. For low-grade gliomas (n=153, 114 cases of OPG and 39 other non-STR/NTR or progressive cases) under SIOP-LGG 2004, 5y-PFS/OS rates were 77.6±5.2% and 92.4±3.2%; Comparatively, among 63 cases of high-grade gliomas, 19 cases survived with median survival of 52 months, 44 cases died. Choroid plexus cancers (n=13) were treated according to CPT-SIOP-2009 with 5y-PFS /OS of 68.4 ± 13.1 % and 64.8±14.3 %. Among 109 germ cell tumors, 5y-PFS/OS were 93.8±2.8% and 95.5±2.2%, respectively. CONCLUSION: The prognosis of CNS tumors are related to pathology, molecular type and individualized therapy. By international multicenter cooperation and adopting advanced protocols, the survival rates of pediatric CNS tumors can be significantly improved.

The use of proton radiation therapy in a patient with melanotic neuroectodermal tumor of infants of the anterior fontanel: description of a clinical case

Melanotic neuroectodermal tumor (MNET) of infants is a rare benign neoplasm detected mainly in children of the first year of life. Standard therapy consists of radical surgical removal of the tumor. Currently, the treatment of patients with recurrent and unresectable forms of the disease is relevant. The number of publications using polychemotherapy and radiation therapy is extremely limited. This article describes a clinical case of the occurrence of MNET in the anterior fontanel with a recurrent course. Proton radiation therapy was chosen as an alternative treatment method.

Melanin Pigmented Odontogenic Lesions- Report of a Dentigerous Cyst and Review of the Literature

<h3>Introduction</h3> The presence of melanocytes in the oral cavity, especially in the gingiva and buccal mucosa is a well documented finding, especially in dark complexioned individuals. Melanocytes are quite rare in odontogenic cysts and tumors. The melanotic neuroectodermal tumor of infancy was initially considered to be the only pigmented jaw tumor in existence. This was until 1961 when Lurie et al reported the first melanin pigmented calcifying odontogenic cyst. In 1964, Grand and Marwah reported the first case of a pigmented odontogenic cyst, that of a gingival cyst. Although most pigmented odontogenic cyst are odontogenic keratocysts, pigmented dentigerous cyst are second in frequency with three cases reported to date. <h3>Materials and Methods</h3> A case of a macroscopic and microscopic melanin pigmented dentigerous cyst is presented with histological and immunohistochemical findings. A pubmedline search of the literature was conducted to review all cases of melanin pigmented odontogenic cysts and neoplasms reported to date. <h3>Results</h3> The pigment in the lesion was confirmed to be melanin by Masson- Fontana staining. The presence of dendritic melanocytes within the lesion was demonstrated by S-100 immunostaining. Since 1961, sixty-three melanin pigmented odontogenic cysts and tumors have been reported. The odontogenic pigmented lesions found in the literature differ in type, histochemical, Immunohistochemical and ultrastructural methods used and have demonstrated that the pigment is always melanin. Most of the patients are Asians and Blacks, thereby implicating racial pigmentation as an important factor. <h3>Conclusion</h3> We report a melanin pigmented dentigerous cyst associated with impacted teeth 16 and 16A in a 27 year old black male. Our dentigerous cyst demonstrated macroscopic and microscopic visible melanin pigmentation. Melanin pigmented dentigerous cysts are quite rare with only three other cases reported to date in the English language literature to which we add this first case involving the maxilla.

Calvarial melanotic neuroectodermal tumor of infancy: A rare case report

Abstract Background: Melanotic neuroectodermal tumor of infancy (MTNI) is a rare congenital tumor of neural crest origin. It is a locally aggressive tumor affecting infants during the first year of life. It commonly arises in the maxilla, mandible, and in the cranial vault. MTNI is usually a benign lesion. Occasionally, it may turn malignant. Though the tumor can be detected by computed tomography and magnetic resonance imaging, an exact diagnosis can only be made by histopathology and immunostaining. Complete surgical excision of the tumor is the gold standard treatment of choice. Benign cranial vault tumors have a good prognosis in contrast to malignant tumors. Case Description: A 3-year-old male child was brought by his mother to the outpatient department with complaints of a large swelling on the left temporal-parieto-occipital region. Computed tomography and magnetic resonance imaging were done which revealed a large hyperdense and hypointense mass in the left temporal-parieto-occipital region with lytic alterations in the skull. The tumor was excised, and tissue sent for histopathology and immunostaining, which revealed a diagnosis of a malignant neuroectodermal tumor of infancy. The patient recovered well in the follow-up period. Conclusion: We report an exceedingly rare case of giant malignant neuroectodermal tumor of infancy (progonoma).

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Odontogenic and Maxillofacial Bone Tumours.

The 5th edition of the World Health Organization (WHO) Classification of Head and Neck Tumours (2022) comes out only five years after the previous edition, however it presents important updates that run in parallel with the rapid progression involving the increasingly sophisticated molecular investigation and its interpretation, some of which already have therapy-related impact. This manuscript provides an overview of the leading changes introduced in the classification of Odontogenic and Maxillofacial Bone Tumours that encompasses cysts of the jaws, odontogenic tumours, giant cell lesions and bone cysts, and bone and cartilage tumours. This is the first edition that Essential and Desirable Diagnostic Features were added for each entity, so that the most important clinical, microscopic and/or radiologic features were encapsulated and briefly highlighted. Surgical ciliated cyst was added to the group of odontogenic cysts, adenoid ameloblastoma was a newly recognized benign epithelial odontogenic tumour, and segmental odontomaxillary dysplasia was introduced in the group of fibro-osseous tumours and dysplasia. In addition, rhabdomyosarcoma with TFCP2 rearrangement, was introduced into the group of malignant jawbone tumours. The unique genetic aberrations distinguish it from other types of rhabdomyosarcomas. On the other hand, melanotic neuroectodermal tumour of infancy and osteoid osteoma were deleted from the benign bone and cartilageneous tumours, as was the hematolymphoid tumour of solitary plasmacytoma of bone. We systematically reviewed each entity in this chapter and provided important updated findings for selected topics that can further aid in the diagnostic process for challenging cases, broaden insights on the logic of the present classification, and finally, emphasize the potential that some of the molecular results may have in the near future to set new treatment approaches.

PIGMENTED NEUROECTODERMAL TUMOR IN MAXILLA OF AN INFANT : REPORT OF A RARE NEOPLASM IN BANDUNG, INDONESIA

Introduction: Melanotic neuroectodermal tumor of infancy (MNTI) is a rare, locally invasive, fast-growing neoplasm with a high recurrence rate, which usually affecting children under 1 year of age. The tumor originated from the neural crest, most commonly found in the head and neck region, especially in the maxilla. Current standard for treatment is by surgical excision, but the high recurrency rate (10% - 60%) and the possiblity of malignant transformation makes the extent of excision debatable. Case report: An 8 -months-old boy was referred to our department with a rapidly growing mass in the anterior of the maxilla since two months prior. The mass was bluish in color, firm, and non-ulcerative. We treated the patient with excision under general anesthesia. Pathology examination was done and MNTI was confirmed. There is no recurrency at 2 years follow-up. Summary: Diagnosis and treatment of MNTI must be done meticulously due to the aggressive nature of the tumor. Wide surgical excision is the best treatment for this case, and routine follow-up must be done to detect any reccurency. Keywords: melanotic neuroectodermal tumor; infancy; maxilla, surgical excision

Melanotic Neuroectodermal Tumor of Infancy —A Rare Case of an Encapsulated Tumor

Melanotic neuroectodermal tumor of infancy (MNTI) is a rare benign, locally invasive neoplasm afflicting the infant more often in the craniofacial region. The current understanding is that this tumor’s origin is neural crest cells. The typical presentation is that a rapidly growing non-ulcerated anterior maxillary mass occurs in an infant usually less than six months old. This tumor may involve other areas including the ovaries, epididymis, femur, mandible, and brain. We present that an 8-month-old infant with a maxillary lesion of MNTI appeared encapsulated, which is a hitherto unreported feature. Investigations leading to the diagnosis and the management of the case are also presented. The need to report cases of this rare entity cannot be overemphasized as this will go a long way in adding new knowledge about its biological nature.

A case report of atypical malignant melanotic neuroectodermal tumor of infancy

Melanotic neuroectodermal tumor of infancy is a rare neoplasm that predominantly involves cranial bones and tends to occur during the first year of life. About 500 cases have been described in the literature to date; 6% of them have been reported to be malignant. Treatment for these malignant tumors was not documented and often turned out to be ineffective.Here we report a case of a child aged 2 years and 4 months who presented with a rapidly growing mass in the maxillary region spreading through the orbit into the anterior cranial fossa. The patient’s parents gave consent to the use of their child’s data, including photographs, for research purposes and in publications. He was treated at the Russian Children’s Clinical Hospital from July 2018 to November 2019. The child underwent chemoradiation and staged surgical removal of the tumor. Treatment with ICE and radiation therapy led to a significant reduction of the tumor volume and enabled us to perform cytoreductive surgery with the removal of the mass in the maxilla. Further treatment according to the CWS 2009 guidance for high-risk patients with NRSTS (NonRhabdomyosarcoma Soft Tissue Sarcoma) and radiation therapy resulted in further regression of intraorbital and intracranial components of the tumor and we performed a radical resection of the residual tumor conglomerate. Investigations during the course of treatment revealed no signs of metastatic involvement. The behavior of malignant melanotic neuroectodermal tumors of infancy is unpredictable, that is why in case of the massive involvement of the facial bones when surgery is associated with a high risk of functional impairment or cosmetic deformity, one should consider preoperative chemotherapy to reduce tumor size and intraoperative blood loss. Moreover, chemotherapy in combination with resection makes it possible to minimize the risk of local relapse or metastasis.

Orthodontic Treatment for a Child with Melanotic Neuroectodermal Tumor during Infancy: A Case Report

Background: Melanotic neuroectodermal tumor of infancy (MNTI) is a very rare tumor, and case reports of orthodontic treatment for patients with MNTI may be previously unreported. This article describes the orthodontic treatment for a 7-year-old girl with MNTI in the mandible. Case: Her chief complaint was anterior crossbite. Although she had an MNTI diagnosis at the age of 8 months, it remained subclinical. Therefore, she has been regularly followed-up by computed tomography (CT) and magnetic resonance (MR) imaging without aggressive treatment. We had worried about the stimulation of MNTI on the mandible by changing her occlusal position with orthodontic treatment. Therefore, we sufficiently explained to her and her family that orthodontic treatment was at risk for worsening MNTI. However, they desired treatment that consisted of maxillary protraction and slow expansion to correct anterior crossbite and encourage the permanent tooth eruption. After 19 months of active orthodontic treatment, the anterior crossbite was improved, and the eruption of permanent teeth made good progress. No evidence of progression and exacerbation of MNTI has been found by both CT and MR imaging. As the observation period is still short, we need a careful and long-term follow-up of her occlusion and MNTI. Furthermore, when we encounter rare cases without previous experience and reports, informed consent was of particular importance.