Case Of Solitary Fibrous Tumor Research Articles

A Dedifferentiated Solitary Fibrous Tumor of Soft Tissue With Retiform and Papillary Features: Report of a Case and Review of the Literature

Abstract We report a case of a dedifferentiated solitary fibrous tumor (SFT) arising in the arm of a 74-year-old man, with the dedifferentiated component showing a unique retiform and papillary architecture. The patient presented with a tumor first noticed 12 years ago, which was diagnosed as a schwannoma. It remained clinically stable for about 10 years until he noticed growth of the mass 2 years ago. On comparative magnetic resonance imaging scans, while most of the tumor did not show major changes, a proximal lobule demonstrated increase in its size. After a new biopsy, which was interpreted as malignant, preoperative radiotherapy and surgical excision were performed. The surgical specimen had areas of typical SFT, with diffuse immunohistochemical expression of STAT6 and only focal CD34 and p16. The lobule that demonstrated growth showed a much more cellular, retiform/papillary proliferation, with plump atypical cells, necrosis, diffuse expression of STAT6 and p16, and complete lack of CD34 expression. With next-generation sequencing, the NAB2(3)-STAT6(18) fusion transcript was detected in both areas of the tumor. Only a few cases of SFT with papillary or retiform/papillary features were reported, most of them in the central nervous system, and none of them interpreted as a dedifferentiated SFT. To the best of our knowledge, these morphological features have not been reported in SFT of the soft tissue or in dedifferentiated SFT of any site. We think pathologists should be aware of this rare finding, which becomes particularly challenging in small biopsies or if classic areas of SFT are not found.

A Case of Solitary Fibrous Tumor in the Obturator Foramen

A Case of Solitary Fibrous Tumor in the Obturator Foramen

A case of solitary fibrous tumor arising in the meninge

A case of solitary fibrous tumor arising in the meninge

A Case of Solitary Fibrous Tumor of the Palate with Signs of Malignancy

A Case of Solitary Fibrous Tumor of the Palate with Signs of Malignancy

Solitary Fibrous Tumor Low Rectum Simulating Cancer

Introduction: The solitary fibrous tumor is a benign mesenchymal tumor of rare extra-pleural location. We report a case of solitary fibrous tumor observed in the lower rectum simulating cancer. The objective was to discuss the diagnostic and therapeutic management of the solitary fibrous in Madagascar. Observation: This is a sixty-five-year-old man, seen in consultation for dyskinesia, with no family history of neoplasia. The digital rectal examination revealed a large, non-budding, firm mass at the level of the right posterolateral surface with a lower pole located 2 cm from the anal margin, the remains of the physical examination are normal. Abdominal computed tomography showed a mass measuring 8 × 7 × 5.5 cm at the expense of the rectal wall of regular tissue density, without a mesenteric node or secondary localization. the biopsy had not found any malignant cells. This result is due to insufficiently deep biopsy samples of the mass, which led us to perform a complete surgical excision by coloprotectomy. The operative follow-up to which was simple. Immunohistochemical study of the surgical specimen confirmed the diagnosis with a positive CD 34 marker. The outcome was favourable without metastasis or recurrence after a six-month follow-up. Conclusion: The rectal localization of the solitary fibrous tumor is exceptional. The diagnosis is histological confirmed by the immunohistochemical study with a positive CD 34 marker.

A Case of Solitary Fibrous Tumor of the Maxillary Sinus Resected by Endoscopic Medial Maxillectomy

A Case of Solitary Fibrous Tumor of the Maxillary Sinus Resected by Endoscopic Medial Maxillectomy

Clinicopathologic and Immunohistochemical Characteristics of Solitary Fibrous Tumor and Its Mimics: A Single-Center Experience

Background:Solitary fibrous tumor (SFT) is a fibroblastic tumor that has been originally reported as a pleural tumor but now has been defined as a tumor that can be seen everywhere in the human body. Histopathologically, many of the fibroblastic tumors can mimic SFT, and immunohistochemistry is necessary for differential diagnosis. Several markers have been used, and recently, STAT6 has been introduced as a diagnostic marker. No research study has been reported from Iran.Objectives:In this report, we are trying to introduce our experience about the clinicopathologic findings of 35 cases of SFT during the last 10 years from our center with an emphasis on the diagnostic role of STAT6 in this tumor.Patients and methods:During the last 10 years, we confirmed the diagnosis of 35 cases of SFT in the pathology archives of Shiraz University of Medical Sciences. These 35 cases were considered as cases. All the clinicopathologic findings were also extracted from the clinical charts of the patients. To evaluate the diagnostic role of STAT6, another 35 cases of spindle cell tumors were also extracted from the pathology archives as mimickers of SFT. STAT6 was stained in all of the 70 cases and controls.Results and discussion:Our experience showed that SFT is more common in middle-aged men with a wide age range, although it is very rare in children. It can be present in every location with a wide size range from less than 1 cm to more than 15 cm. The presence of abnormal staghorn vessels is one of the main diagnostic histopathologic characteristics. STAT6 showed a sensitivity and specificity of 91% and 86% in the diagnosis of SFT. Other markers such as CD99, CD34, and BCL2 have also been considered useful in the differential diagnosis of this tumor, although the diagnostic accuracy seems to be lower than STAT6. High mitosis, presence of necrosis, and atypia are important criteria for predicting malignant and aggressive behavior in SFT. Among 35 cases in our study, 17% showed malignant behavior as recurrent or metastatic tumors.Conclusion:Solitary fibrous tumor is a common soft tissue tumor that can be seen everywhere and needs careful histopathologic and immunohistochemical evaluation for the correct diagnosis and prediction of aggressive or benign behavior.

Radiological, histopathological, and immunohistochemical characterization of solitary fibrous tumor of the lacrimal sac: A rare case report

Solitary fibrous tumor (SFT) is a benign spindle cell neoplasm of mesenchymal fibroblast cells. It can appear in various locations, but SFT of the lacrimal sac is rare. Due to their variable clinical, histological, and radiological presentation, it can be easily misdiagnosed. We report a rare case of SFT of the lacrimal sac with its radiological, histological, and immunochemical characterization.

A Case of Huge Solitary Fibrous Tumor with Maxillary Sinus Wall Destruction Masquerading as Maxillary Sinus Cancer

Solitary fibrous tumors (SFT) are rare fibroblastic mesenchymal neoplasms which are originally described as neoplasms of the pleura originating from the spindle cells. Although it can originate from extrapleural sites including the head and neck, it is exceedingly rare in the sinonasal tract. There has been no reported cases of SFT involving the paranasal sinuses in Korea; however, there was case of a 34-year-old man who presented with persistent left nasal obstruction and watering of the left eye. Imaging by CT and MRI revealed a large, highly vascular tumor occupying the maxilloethmoidal sinus cavities associated with bony wall destruction, masquerading as maxillary sinus cancer. The tumor mass occupying sinus cavities was removed through endoscopic and Caldwell-Luc approach. Histopathological examination of the tumor was consistent with SFT. We report this case to further insights regarding the diagnosis and management of this rare tumor.

A Case of Solitary Fibrous Tumor in the External Auditory Canal

Solitary fibrous tumor (SFT) is a rare benign spindle-cell neoplasm, most often found in the pleura. Recently, it has been reported to appear throughout the body but rarely in head and neck region. Tumors in the external auditory canal, in particular, have been very rarely reported. We experienced a case of a 55-year-old male with a 6-month history of progressive swelling from the orifice of left external auditory canal. The tumor was round, well circumscribed, almost completely obstructing the left external auditory canal. On the enhanced temporal bone CT and enhanced paranasal sinus MRI, a 2.0×1.7 cm sized mass was observed at the left external auditory canal. He was treated with surgical excision under general anesthesia. Histopathologic examination confirmed the diagnosis of SFT. This case report presents a rare case of a SFT arising in the external auditory canal.

Histopathological findings and immunohistochemical expression of the stem cell markers CD44, ALDH1, Bmi-1, and Nanog in oral solitary fibrous tumors

The aim of this study was to evaluate the histomorphologic presentation and the expression of stem cell-related markers in a series of oral solitary fibrous tumors (SFTs). Histopathological variables and the expression of the standard stem cell markers CD34 and CD99, used for SFT diagnosis, as well as STAT6 were evaluated in 13 oral SFTs. The expression of the cancer stem cell markers CD44, ALDH1, Bmi-1, and Nanog and the tumor suppressor gene p16Ink4a were also investigated. The majority of oral SFTs were circumscribed and characterized by a proliferation of spindle cells arranged in a hyalinized stroma. Only 2 oral SFTs showed >4 mitoses/10 high-power fields. Hypercellularity as well as nuclear and cellular pleomorphism were classified as low and moderate in most of the oral SFTs. All oral SFTs were positive for CD34, STAT6, CD44, ALDH1, Bmi-1, and p16Ink4a. CD99 and Nanog expression was observed in 11 and 10 oral SFT cases, respectively. We suggest that STAT6 and ALDH1 have relevant diagnostic value. The expression of CD44, ALDH1, Bmi-1, and Nanog, which is observed in cancer stem cells, may confer advantages to oral SFT cells.

Clinicopathological characteristics of myxoid solitary fibrous tumor: analysis of seven cases

Objective: To investigate the clinicopathological characteristics, immunophenotypes, and diagnostic and differential diagnostic features of myxoid solitary fibrous tumor (SFT). Methods: Seven cases of myxoid SFT were collected from the archives of Zhejiang Provincial People's Hospital from January 2014 to December 2019. The clinical features, histomorphology, immunohistochemistry, molecular genetics and prognosis were analyzed and the relevant literature was reviewed. Results: There were three male and four female patients ranging from 32 to 67 years. Locations included the pleura (three cases), pelvic cavity, vagina, parotid gland, and nasal cavity(one each). Tumor size ranged from 2.7 to 13.5 cm. Histologically, all cases were characterized predominantly by the presence of myxoid stroma comprising 55% to 90% of the tumor (mean 72%). The tumors were composed of predominantly stellated, spindled or ovoid cells disposed haphazardly, in loose fascicles, or in anastomosing strands imparting a microcystic/reticular appearance in a extensively myxoid, richly vascularized stroma. Staghorn-shaped branching vessels and thin strands of collagen were commonly seen between tumors cells amidst the myxoid background. These myxoid areas were punctuated by small cellular areas showing diagnostic features of classical SFT, which were present in all seven cases. Areas showing giant cell angifibroma-like change were noted in 2 cases and focal lipomatous metaplasia was identified in 1 case. Atypical features suggestive of aggressive behavior were present in 2 cases and in one of the cases myxoid SFT with high-grade sarcomatous overgrowth was noted. Immunohistochemically, tumor cells in all cases stained positively for STAT6 and CD34. Polymerase chain reaction technique showed in both the examined cases the characteristic NAB2ex4-STAT6ex2 fusion gene. According to the Demicco's risk assessment model, four cases were classfied as low, one was classified as moderate and 2 was classified as high. Follow-up information was obtained in 4 cases. One tumor recurred 3 times within 48 months after operation, and the other 3 cases had no tumor recurrence and metastasis. Conclusions: Myxoid SFT represents a rare morphologic variant of SFT with biological behaviors ranging from indolent to aggressive. Myxoid SFT should be included in the differential diagnostic spectrums of soft tissue tumors with significantly myxoid change. Carefully searching for the typical SFT histomorphology with the use of immunohistochemistry and if necessary, molecularly testing for NAB2-STAT6 fusion can help to distinguish myxoid SFT from its many mimickers.

Case report: uniportal video-assisted thoracoscopic resection of a solitary fibrous tumor preoperatively predicted visceral pleura origin using dynamic chest radiography

BackgroundDynamic chest radiography (DCR) is a flat-panel detector (FPD)-based functional X-ray imaging, which is performed as an additional examination in chest radiography. DCR provides objective and quantifiable information, such as diaphragm movement, pulmonary ventilation and circulation, and is reasonable for detecting tumor invasion or adhesion.Case presentationWe present a case of Solitary Fibrous Tumor of Pleura (SFTP), preoperatively predicted visceral pleura origin using Dynamic chest radiography (DCR) and surgically resected through single-access (uniportal) video-assisted thoracoscopic surgery (UVATS).ConclusionsUVATS may be a suitable surgical option for pedunculated SFTPs. Dynamic chest radiography provides information, such as tumor invasion or adhesion and helpful for predicting origin of the tumor.

Orbit Solitary Fibrous Tumor: A Proposed Risk Prediction Model Based on a Case Series and Comprehensive Literature Review.

Solitary fibrous tumors (SFTs) of the orbit are rare. In order to further characterize the clinical and pathologic features of solitary fibrous tumor arising at this anatomic site, 12 cases of orbital SFTs were analyzed in conjunction with a review of 263 cases reported from the English literature in order to develop a risk prediction model. SFTs of the orbit were equally distributed between males (n = 5) and females (n = 7) with a mean patient age of 46.8years (median 44.5years; range 18-76years) at initial diagnosis. The patients typically presented with swelling or mass around the orbit, with proptosis (n = 10), ptosis (n = 5), and visual changes (n = 6). Tumors were orbital (n = 10) or upper eyelid (n = 2). Mean tumor size was 2.5cm (median 2.6cm). Microscopically, the tumors were characterized by cytologically bland spindle cells with patternless growth, hypocellular and hypercellular areas, variable amounts of collagen, and ectatic, branching blood vessels. By immunohistochemistry, all cases had a strong nuclear STAT6 expression. All patients were initially managed with excision or biopsy, three with presurgical embolization. The two patients with biopsy only had persistent disease (mean 37.2months), but a third patient developed distant bone metastasis at 86.9months. Overall mean follow-up was 73.1months: 9 patients are alive or dead without disease (mean 77.9months), two patients with persistent disease,and one patient with metastatic disease at last follow-up (102months). Incorporating cases sufficiently reported in the literature, a risk prediction model based on age > 45years, tumor size > 3cm, tumor necrosis, mitoses of > 4/2 mm2, moderate to high cellularity, and moderate to severe pleomorphism allows for risk stratification for the development of local recurrence and distant metastasis. In conclusion, orbital SFTs are rare, but can be reliably diagnosed based on the presence of characteristic morphologic features and STAT6 immunohistochemistry. Orbital tumors tend to show a higher frequency of local recurrence than distant metastasis, which can be predicted by a risk stratification model unique to orbital tumors. With late disease common, long term clinical follow-up is recommended.

The Diagnostic and Clinical Significance of TFE3 Immunohistochemical Nuclear Expression in Solitary Fibrous Tumour.

The expression of TFE3 (transcription factor E3) in solitary fibrous tumours (SFTs) and their histologic mimickers was investigated, and the diagnostic value and clinical significance of TFE3 nuclear expression in SFTs were explored. Immunohistochemical analysis for TFE3 was performed on 50 cases of SFTs that were surgically resected. The controls were sample tissues from malignant peripheral nerve sheath tumour, synovial sarcoma, dedifferentiated liposarcoma, spindle cell lipoma, and dermatofibrosarcoma protuberans. The survival of patients with TFE3-positive and TFE3-negative expressions was assessed through the Kaplan-Meier analysis. In 44 of 50 (88%) SFTs, nuclear immunoreactivity for TFE3 was detected. The TFE3 expression was negative in all samples of synovial sarcoma, malignant peripheral nerve sheath tumour, dermatofibrosarcoma protuberans, and spindle cell lipoma and weakly positive in 2 of 10 cases of dedifferentiated liposarcoma. Fluorescence in situ hybridization (FISH) confirmed that the expression of the TFE3 protein is not caused by gene translocation. There was no statistical significance between the association of the TFE3 expression and SFT patient prognosis. Therefore, TFE3 is capable of enhancing the differential diagnosis of SFTs and their histologic mimickers and can be potentially used as a diagnostic marker. The findings also offer valuable insights into SFT diagnosis, aetiology, and associated molecular mechanisms.

Clinical and pathological analysis of 64 patients with primary neoplasms of the lacrimal drainage system

Objective: To analyze the pathological classification and age distribution of primary neoplasms of the lacrimal drainage system. Methods: Retrospective case series study. A total of 64 patients (65 eyes) were diagnosed with primary neoplasms of the lacrimal drainage system and received surgery at Tianjin Eye Hospital from January 2006 to December 2016. All the clinical data of the patients were analyzed, including gender, diseased eye, age, clinical manifestations, composition of benign and malignant masses, and prognosis. The histopathological composition and age distribution of patients with primary lacrimal mass, lacrimal duct mass and lacrimal sac mass were analyzed according to the different diseased sites. Results: Twenty-three patients (24 eyes) were male, and 41 patients (41 eyes) were female. The right eye was involved in 36 patients, the left eye in 27 patients, and both eyes in one patient. The age at diagnosis ranged from 12 to 78 years old [mean, (46±4) years]. The course of disease was (13.1±4.2) months, ranging from 1 month to 7 years. The chief complaint was tear discharge in 43 patients, tumor in 19 patients, and abscess discharge in 2 patients. There were 29 patients with angular displacement and 21 patients with swelling pain. There were 51 patients with benign lesions, 4 with borderline lesions, and 9 with malignantlesions. These neoplasms consisted of primary peripunctal neoplasms in 17 patients, primary canalicular neoplasms in 2 patients, and primary lacrimal sac neoplasms in 45 patients. All primary peripunctal neoplasms (17 cases) were benign, among which nevi (10 cases) occupied the first place. All primary canalicular neoplasms (2 cases) were benign, there were 1 case of epidermoid cysts and 1 case of degenerative disease. Among the primary benign lacrimal sac masses (32 cases), mucous epithelial cysts (9 cases), dermoid cysts (6 cases), and epidermoid cysts (6 cases) occupied the first three places. Among the primary borderlin lacrimal sac masses (4 cases), there were 2 cases of giant cell tumor of soft tissue, 1 case of solitary fibrous tumor, and 1 case of inflammatory myofibroblastic tumor. The primary malignant mass of lacrimal sac (9 cases) was dominated by squamous cell carcinoma (3 cases). In terms of age distribution, the patients with primary peripunctal mass were mainly in the group of 40-59 years old (14 cases). The primary benign mass of lacrimal sac mainly occurred in the group of less than 40 years old (15 cases) and the group of 40-59 years old (11 cases). The patients with primary lacrimal sac borderline and malignant masses were all in the groups of over 40 years old. A total of 49 patients were followed up for 27 months to 16 years. The average follow-up time was (57.2±3.8) months. Lacrimal sac transitional cell carcinoma relapsed 7 months after surgery in one patient, and lacrimal sac melanoma relapsed 1 year after surgery in one patient. The patients did not relapse in 24 months and 38 months after surgery respectively. There were no recurrence of other cases. Conclusions: Primary peripunctal neoplasms are mostly characterized with benign lesions, among which nevi are most common. Mucous epithelial cysts, epidermoid cysts, and dermoid cysts are the major benign lacrimal sac neoplasms. Squamous cell carcinomas are the most common malignant lacrimal sac neoplasms. The malignant tumor of lacrimal sac often occurs in the middle-aged and elderly patients. (Chin J Ophthalmol, 2020, 56: 364-369).

Orbital solitary fibrous tumors: a multi-centered histopathological and immunohistochemical analysis with radiological description.

ABSTRACTBACKGROUND: Solitary fibrous tumors (SFT), formerly called hemangiopericytoma, are rare tumors derived from mesenchymal cells originally described in the pleura, but these tumors may affect extraserosal tissues including the lacrimal gland and orbit.OBJECTIVE: Conduct a multi-centered clinical, radiological and histopathological analysis of 17 orbital SFT cases.DESIGN: A retrospective case series.SETTING: Three eye centers in two countries.PATIENTS AND METHODS: The data collected from the charts of 17 adult patients presenting with tissue diagnosis of orbital hemangiopericytoma or SFT from January 2003 to December 2018 included demographics, clinical imaging and histopathological information including immunohistochemical (IHC) characteristics.MAIN OUTCOME MEASURES: The demographic characteristics, clinical presentation, and histopathological patterns or variants of SFT were analyzed.SAMPLE SIZE: 17 adult patients.RESULTS: Mean age was 45 years (range 23-80 years). Male to female ratio was 3:1. The right eye was affected in 12 (70.5%) patients. Commonest presentation was proptosis in 13/17 (76% of patients). Other symptoms were impaired motility (29%) and ptosis (11%). Lesions mostly affected the medial orbit (35%), then orbital apex in 11%. The histopathological classic pattern-less variant was the commonest. One case with aggressive behavior, multiple recurrences and atypical features was encountered. Immunohistochemical (IHC) markers used included CD34 expression in all cases, Bcl-2 expression in 10/11, CD99 in 9/9 and Vimentin in 4/4. STAT6 was used in 2 cases.CONCLUSIONS: SFTs are rare tumors affecting the orbit in both genders equally in their mid-forties, but showed male predominance in our analysis with a predominant classic histopathological pattern. Tissue diagnosis is essential and requires IHC studies for confirmation.LIMITATIONS: Sample size is relatively small owing to the rarity of this tumor in the orbit.CONFLICT OF INTEREST: None.

Rare variants of solitary fibrous tumor

ObjectiveSome cases of solitary fibrous tumor (SFT) exhibit unusual histologic features that may cause diagnostic difficulty, such as fascicular monotonous spindle cells accompanied by hyalinized blood vessels and numerous evenly distributed mast cells, and features mimicking myxoid liposarcoma. Awareness of these features is important for reaching correct diagnosis of similar cases. MethodsThree cases of SFT with the above unusual features were retrieved from our consult files for review, including H&E slides and immunohistochemical stains. In addition, FISH analysis for SS18-SSX (SYT), DDIT3 and MDM2 were performed. Furthermore, formalin-fixed paraffin-embedded (FFPE) tissue sections were tested for 8 fusion variants of NAB2-STAT6 by qualitative endpoint reverse-transcriptase (RT)-PCR. ResultsNeoplastic cells from all 3 cases are positive for CD34, CD99, and STAT6 immunohistochemically. In addition, the tumors are positive for NAB2-STAT6 fusion gene. Mast cells from the first case possess nonneoplastic phenotype and are positive for CD117 and tryptase staining but negative for CD25. ConclusionsThe three cases studied here represent rare types of SFT, which differ from classical “pattern-less” pattern of SFT. Correct diagnosis required a combination of CD34 and STAT6 immunostaining and NAB2-STAT6 fusion gene analysis.

STAT6 Expression in Solitary Fibrous Tumor and Histologic Mimics: a Single Institution Experience.

STAT6 stain has proved to be a good surrogate marker for the genetic alteration (NAB2-STAT6 gene fusion) in solitary fibrous tumor (SFT). This study aims to validate the use of STAT6 rabbit monoclonal antibody in differentiating SFT from its histologic mimics. Forty-five cases of SFT and 110 cases from 9 other spindle cell tumors were collected for STAT6 immunostaining. Positive nuclear STAT6 staining was present in all 45 SFT cases (100% sensitivity). No nuclear staining was identified in other spindle cell neoplasms (0/13, dedifferentiated liposarcoma; 0/17, synovial sarcoma; 0/16, malignant peripheral nerve sheath tumors; 0/25, undifferentiated pleomorphic sarcoma; 0/10, dermatofibrosarcoma protuberans; 0/9, low-grade fibromyxoid sarcoma; 0/6, angiofibroma; 0/5, deep fibromatosis; 0/9, gastrointestinal tumor). The STAT6 staining in SFT was usually diffuse (5+ in 19 cases; 4+ in 17 cases) and strong (40 cases). Monoclonal STAT6 stain is highly sensitive and specific for SFTs and particularly useful in the diagnosis of difficult SFT cases.

Solitary fibrous tumors of the head and neck region revisited: a single-institution study of 20 cases and review of the literature

A solitary fibrous tumor (SFT) is a rare, NAB2-STAT6 fusion gene-associated mesenchymal neoplasm. It most commonly arises in the pleural site, but it can occur at many other sites, and rarely also in the head and neck (H&N) region. STFs may show many growth patterns and therefore can be easily mistaken for other more common H&N spindle cell or epithelial lesions. In this study, we present our experience in the diagnosis of 20 cases of SFT in the H&N region and discuss their most notable mimickers. In all cases, STAT6 expression was found positive by immunohistochemistry, and the NAB2-STAT6 fusion was confirmed by next-generation sequencing. Three major fusion variants were detected: NAB2ex2-STAT6int1 (5/20, 25%), NAB2ex6-STAT6ex16 (4/20, 20%), and NAB2ex4-STAT6ex2 (3/20, 15%). Clinical follow-up was available for 16 patients (median follow-up time: 84 months). One patient with a morphologically malignant SFT experienced multiple local recurrences, followed by dissemination into the lungs and meninges. This malignant SFT also displayed an aberrant FLI1 expression, which was not previously reported in SFT cases. We also summarize findings from 200 cases of SFT of the H&N region, which included cases from our study, and from previous studies that reported on the fusion status of the STAT6 gene. The results suggest that metastatic disease developed only in cases with STAT6 variants that included the DNA-binding domain (STAT6-full variants), which contradicts expectations from previous reports and deserves further investigation.