High-risk HPV-related squamous cell carcinoma in the temporal bone: a rare but noteworthy subtype.

High-risk human papillomavirus (HPV) is a risk factor for the development of several head and neck squamous cell carcinomas (SCCs). However, there have been few reports of high-risk HPV infection in temporal bone squamous cell carcinomas (TBSCCs), and thus the prevalence and clinicopathologic significance of high-risk HPV in TBSCCs are still unclear. We retrospectively collected 131 TBSCCs and analyzed them for transcriptionally active high-risk HPV infection using messenger RNA in situ hybridization; we also assessed the utility of p16-immunohistochemistry (IHC) and Rb-IHC to predict HPV infection. Eighteen (13.7%) of the 131 TBSCCs were positive for p16-IHC, and five of them were positive for high-risk HPV infection (the estimated high-risk HPV positivity rate was 3.8% [5/131]). Interestingly, all five HPV-positive patients were male and had TBSCC on the right side. In the p16-IHC+/HPV+ cases (n = 5), the Rb-IHC showed a partial loss pattern (n = 4) or complete loss pattern (n = 1). In contrast, all p16-IHC-negative cases (n = 113) showed an Rb-IHC preserved pattern. The positive predictive value (PPV) of p16-IHC positivity for high-risk HPV infection was low at 27.8%, while the combination of p16-IHC+/Rb-IHC partial loss pattern showed excellent reliability with a PPV of 100%. The prognostic significance of high-risk HPV infection remained unclear. High-risk HPV-related TBSCC is an extremely rare but noteworthy subtype.

Acute necrotic disorder of the small intestine post-coronavirus disease-2019 vaccination.

The Pfizer-BioNTech coronavirus disease 2019 (COVID-19) vaccine is extensively used worldwide, and its safety has been proven. Herein, we report a case of an acute necrotic disorder in the small intestine post-COVID-19 vaccination. The patient developed severe abdominal pain the day after the first vaccination. Contrast-enhanced computed tomography showed extensive ileum wall thickening and ascites. Colonoscopy revealed a ring-shaped ulcer and stricture in the terminal ileum. Ileocecal resection was performed, and the patient did not have further episodes of a necrotic disorder in the small intestine. Although it is unknown if this event is associated with vaccination, and this occurrence also does not outweigh the efficacy and safety of the Pfizer-BioNTech COVID-19 vaccine, gastroenterologists need to be aware of this rare case, given its noteworthy timing.

Intermitochondrial signaling regulates the uniform distribution of stationary mitochondria in axons.

In the central nervous system (CNS), many neurons develop axonal arbors that are crucial for information processing. Previous studies have demonstrated that premature axons contain motile and stationary mitochondria, and their balance is important for axonal arborization. However, the mechanisms by which neurons determine the positions of stationary mitochondria as well as their turnover remain to be elucidated. We observed that the distribution of stationary mitochondrial spots along the unmyelinated and nonsynaptic axons is not random but rather relatively uniform both in primary cultured neurons and in tissues. Intriguingly, whereas the positions of each mitochondrial spot changed over time, the overall distribution remained uniform. In addition, local inactivation of mitochondria by KillerRed mediated chromophore-assisted light inactivation (CALI) inhibited the translocation of mitochondrial spots in adjacent axonal regions, suggesting that functional mitochondria enhance the motility of other mitochondria in the vicinity. Signals of ATP:ADP sensor, PercevalHR indicated that the ATP:ADP ratio was relatively high around mitochondria, and treating axons with phosphocreatine (PCr), which supplies ATP, reduced the immobile mitochondria induced by the local mitochondrial inactivation. In a mathematical model, we found that the ATP gradient generated by mitochondria, and ATP dependent regulation of mitochondrial motility could establish uniform mitochondrial distribution. These observations suggest that axons in the CNS possess the system that distributes mitochondria uniformly, and intermitochondrial signaling contribute to the regulation. In addition, our results suggest the possibility that ATP might be one of the molecules mediating the signaling.

Management of Residual Hearing with Cartilage Conduction Hearing Aid after Lateral Temporal Bone Resection: Our Institutional Experience.

BACKGROUND: There is no guideline for hearing compensation after temporal bone resection. This study aimed to retrospectively analyze surgical cases with reconstruction for hearing preservation after temporal bone malignancy resection and propose a new alternative to compensate for hearing loss. METHODS: We retrospectively reviewed the medical records of 30 patients who underwent lateral temporal bone surgery for temporal bone malignancy at our institution and examined their hearing abilities after surgery. RESULT: The hearing outcomes of patients with an external auditory meatus reconstruction varied widely. The mean postoperative air-bone gap at 0.5, 1, 2, and 4 kHz ranged from 22.5 dB to 71.25 dB. On the other hand, the average difference between the aided sound field thresholds with cartilage conduction hearing aid and bone conduction thresholds at 0.5, 1, 2, and 4 kHz ranged from -3.75 to 41.25. More closely located auricular cartilage and temporal bone resulted in smaller differences between the aided sound field and bone conduction thresholds. CONCLUSIONS: There is still room for improvement of surgical techniques for reconstruction of the auditory meatus to preserve hearing after temporal bone resection. The cartilage conduction hearing aid may provide non-invasive postoperative hearing compensation after lateral temporal bone resection.

Corpus callosotomy for drug-resistant epilepsy in a pediatric patient with Waardenburg syndrome Type I.

BACKGROUND: Waardenburg syndrome (WS) is caused by autosomal dominant mutations. Since the coexistence of epilepsy and WS type I is rare, the detailed clinical features and treatment of epilepsy, including surgery, have not been fully reported for these patients. We report the first case of an individual with WS type I, who underwent corpus callosotomy (CC) for drug-resistant epilepsy and obtained good seizure outcomes. CASE DESCRIPTION: A boy was diagnosed as having WS type I and developmental delay based on characteristic symptoms and a family history of hearing loss. He underwent cochlear implantation at 18 months of age. At 4 years of age, he developed epileptic seizures with a semiology of drop attack. Electroencephalography (EEG) showed bilateral synchronous high-amplitude spikes and wave bursts, dominant in the right hemisphere. Based on the multimodality examinations, we considered that ictal discharges propagated from the entire right hemisphere to the left, resulting in synchronous discharge and a clinical drop attack; therefore, CC was indicated. At 9 years of age, he underwent a front 2/3rd CC. At 1 year, the patient became seizure free, and interictal EEG showed less frequent and lower amplitude spike and wave bursts than before. CONCLUSION: When patients with WS Type I and cognitive impairment show drug-resistant epilepsy, clinicians should consider a presurgical evaluation.

Primary Advanced Squamous Cell Carcinoma of the Temporal Bone: A Single-Center Clinical Study.

OBJECTIVES/HYPOTHESIS: The extreme rarity of temporal bone squamous cell carcinoma (TB-SCC) has delayed the accumulation of high-quality clinical evidence. For the purposes of retrospective meta-analysis in the future, a large dataset with information from various institutions would be ideal. Our objective here was to retrospectively review cases of TB-SCC encountered at a single tertiary referral center and explore survival outcomes and prognostic factors. STUDY DESIGN: Retrospective chart review. METHODS: The medical records of all TB-SCC cases were retrospectively reviewed. The resulting dataset contained 71 cases of primary cancer eligible for initial definitive (curative) treatment. RESULTS: T4 status was associated with lower disease-specific 5-year survival than T1 to T3 staging (T1: 100%, T2: 92%, T3: 86%, T4: 51%). Survival was significantly higher in operable than in inoperable cases, even when restricted to advanced (T3/T4) cancers. The tumor extension to the middle ear cavity was observed in 13/17 of T3 cases, but it was not associated with poor survival. In addition, among operable cases, negative surgical margins were associated with significantly higher survival than positive margins. CONCLUSIONS: Definitive treatments can offer disease-specific 5-year survival of over 85% in T1 to T3 cases of TB-SCC. The tumor extension to the middle ear cavity is not associated with poor survival. T4 status, inoperability, nodal invasion, and positive surgical margin are identified as a predictor of poor prognosis. Still, the matter of how to deal with unresectable tumors remains an outstanding issue in the treatment of TB-SCC. LEVEL OF EVIDENCE: 4 Laryngoscope, 131:E583-E589, 2021.

Intrahepatic cholangiocarcinoma with clear cell type following laparoscopic curative surgery.

BACKGROUND: Intrahepatic cholangiocarcinoma (ICC) is the second most common malignancy of primary liver cancer. Among the several pathological types of ICC, only five cases of the clear cell type have been reported, including the one presented below. Here we report a unique case of clear cell type ICC following laparoscopic hepatectomy. CASE PRESENTATION: A 67-year-old woman had a history of hepatitis B virus. Computed tomography revealed a ring-like enhanced mass 35 mm in diameter at segment 7 in the early phase. The enhancement was prolonged to the late phase through the portal phase, while the shape was irregular. Ethoxybenzy magnetic resonance imaging revealed that the tumor had a low signal intensity on T1-weighted imaging and a high signal intensity on T2-weighted imaging. Diffusion-weighted images identified that the tumor had remarkably high signal intensity. Tumor enhancement was not detected throughout the tumor in the hepatocyte phase. Upon ICC diagnosis, a laparoscopic S7 subsegmentectomy was performed. The patient's postoperative course was uneventful. An immunohistochemical examination revealed that the cells tested positive for cytokeratin 7 (CK7), CK19, and CD56 and negative for CK20, CD10, α-fetoprotein, thyroid transcription factor-1. At 2 years after surgery, the patient remains alive without recurrence. CONCLUSIONS: Here we presented a case of clear cell ICC that was treated by laparoscopic hepatectomy. Immunological analysis, especially by CD56 and several CK markers, is helpful for diagnosing this disease.

Use of negative pressure wound therapy to treat a cochlear implant infection around the auricle: a case report.

Although negative pressure wound therapy (NPWT) is widely used, its application to the head and neck region remains challenging due to anatomical complexities. This report presents the case of a female patient presenting with mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes, uncontrolled diabetes and severe bilateral sensorineural hearing loss. The patient had undergone cochlear implant surgery and five months later the wound was infected with methicillin-resistant Staphylococcus aureus (MRSA). NPWT was started shortly after removing the internal receiver and was stopped 11 days later. NPWT helped in controlling infection and led to a successful wound closure. In this case, NPWT was effective in treating infectious wounds around the auricle after cochlear implant surgery. Declaration of interest: The authors have no financial support for this article and no conflict of interest directly relevant to the content of this article.

Genetic landscape of external auditory canal squamous cell carcinoma.

External auditory canal squamous cell carcinoma (EACSCC) is an extremely rare and aggressive malignancy. Due to its rarity, the molecular and genetic characteristics of EACSCC have not yet been elucidated. To reveal the genetic alterations of EACSCC, we performed whole exome sequencing (WES) on 11 primary tumors, 1 relapsed tumor and 10 noncancerous tissues from 10 patients with EACSCC, including 1 with a rare case of synchronous bilateral EACSCC of both ears. WES of the primary tumor samples showed that the most frequently mutated gene is TP53 (63.6%). In addition, recurrent mutations in CDKN2A, NOTCH1, NOTCH2, FAT1 and FAT3 were detected in multiple samples. The mutational signature analysis of primary tumors indicated that the mutational processes associated with the activation of apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) deaminases are the most common in EACSCC, suggesting its similarity to SCC from other primary sites. Analysis of arm-level copy number alterations detected notable amplification of chromosomes 3q, 5p and 8q as well as deletion of 3p across multiple samples. Focal chromosomal aberrations included amplifications of 5p15.33 (ZDHHC11B) and 7p14.1 (TARP) as well as deletion of 9p21.3 (CDKN2A/B). The protein expression levels of ZDHHC11B and TARP in EACSCC tissues were validated by immunohistochemistry. Moreover, WES of the primary and relapsed tumors from a case of synchronous bilateral EACSCC showed the intrapatient genetic heterogeneity of EACSCC. In summary, this study provides the first evidence for genetic alterations of EACSCC. Our findings suggest that EACSCC mostly resembles other SCC.

Therapeutic effect of Nivolumab for advanced / recurrent temporal bone squamous cell carcinoma.

OBJECTIVE: The immune checkpoint inhibitor Nivolumab was approved for the treatment of platinum-refractory head and neck squamous cell carcinoma (SCC), expanding the treatment options for recurrent or advanced head and neck SCC. However, since temporal bone squamous cell carcinoma (TB-SCC) is very rare cancer, the effectiveness of Nivolumab remains unclear. We investigated the effects of Nivolumab for TB-SCC. METHOD: Chart information was collected for all patients who underwent the first administration of Nivolumab for recurrent or residual TB-SCC in our hospital between September 2017 and December 2019. Tumor staging followed the modified Pittsburgh classification. Changes in the tumor burden and survival outcome were examined. RESULTS: We examined 9 patients with recurrent or residual TB-SCC who started administration of Nivolumab. In these cases, recurrent or residual SCC was observed after chemotherapy and/or chemoradiotherapy including platinum. The duration of Nivolumab was 2-54 weeks (median 20.0 weeks). The evaluation of the therapeutic effect according to the RECIST method showed partial response in 1 case, stable disease in 2 cases, progressive disease in 4 cases, and size unevaluated in 2 case. Although the number of cases was small, comparing with 5 cases without Nivolumab, these cases showed longer overall survival (1-year OS 33.3% vs 20.0%). CONCLUSION: We used Nivolumab as palliative chemotherapy in 9 patients with recurrent/residual TB-SCC, and we were able to obtain a certain therapeutic effect on TB-SCC as well as other head and neck SCC.

Malignant perivascular epithelioid cell tumor mimicking jugular foramen schwannoma: A case report and literature review.

BACKGROUND: Perivascular epithelioid cell tumors (PEComas) of the skull base are extremely rare. Here we report the first description of a malignant PEComa mimicking jugular foramen schwannoma and presenting as Collet-Sicard syndrome, and we review the previous literature on PEComas of the head, neck and skull base. CASE DESCRIPTION: A 29-year-old woman presented with hoarseness, dysphagia, vomiting, and headache. She was first diagnosed with Collet-Sicard syndrome caused by thrombosis of the sigmoid and transverse sinuses. She was treated with anticoagulant therapy, and the hoarseness and paralysis of the accessory nerve improved. Later, at age 31, the hoarseness again worsened. At another hospital, enhanced computed tomography revealed a tumor in the jugular foramen extending to the neck and medially displacing the internal carotid artery. She was referred to our hospital for further examination and was diagnosed with jugular foramen schwannoma causing thrombosis of the sinuses. At the one-year follow-up, the tumor had grown rapidly and had started to surround the internal carotid artery. We therefore performed a tissue biopsy of the tumor in the jugular foramen and neck. Based on pathological analysis, we made a definitive diagnosis of malignant PEComa. CONCLUSIONS: It may be extremely challenging to reach an accurate diagnosis of PEComa in the skull-base region, which can cause a delay in treatment initiation. When atypical clinical features for a skull-base tumor are found, we recommend preliminary biopsy to obtain a definitive diagnosis and initiate an appropriate treatment strategy as early as possible.

Asymmetrical surface scanning registration for image-guided otologic surgery: A phantom study.

OBJECTIVE: To develop a registration procedure to achieve a higher degree of registration accuracy in image-guided otological surgery, paying particular attention to the registration centroid. METHODS: A head phantom was used to measure the target registration error (TRE) at measurement points at various depth from the surface of the head. The surface-matching registration was performed using a commercially available surgical navigation system. We registered the phantom using only one ear of either side (right 100% - left 0%, or right 0% - left 100%) or using both ears with variable ratios (right 75% - left 25%, right 50% - left 50%, or right 25% - left 75%). RESULTS: The overall TRE was the smallest when registration was performed equally on both sides. However, the TRE at 20-50 mm from the surface was the smallest when the fiducial points for the registration were collected asymmetrically at a ratio of 75:25 and weighed heavier on the operating side, and this difference was statistically significant. CONCLUSION: The accuracy of image-guided surgery can be improved by carefully planning the registration procedure without changing the procedure itself. Accurate image-guided surgery at the middle and inner ear was achieved using 75% of the point cloud for the operating side and 25% of that for the opposite side for the registration.

Improved Visualization of Middle Ear Cholesteatoma with Computed Diffusion-weighted Imaging.

Computed DWI (cDWI) is a mathematical technique that calculates arbitrary higher b value images from at least two different lower b values. In addition, the removal of high intensity noise with image processing on cDWI could improve cholesteatoma-background contrast-to-noise ratio (CNR). In the present study, noise reduction was performed by the cut-off values of apparent diffusion coefficient (ADC) less than 0 and 0.4 × 10-3 s/mm2. The cholesteatoma to non-cholesteatoma CNR was increased using a noise reduction algorithm for clinical setting.

Ultrahigh-resolution CT scan of the temporal bone.

OBJECTIVE: Ultrahigh-resolution CT (U-HRCT) provides better spatial resolution than conventional multi-detector row CT (ConvCT) and could be expected to identify microstructures with its 0.25-mm collimation, 1792 channels and 160 detector rows, 0.4 × 0.5 mm focus size, and a 1024 matrix. The aim of the study was to evaluate key anatomic structures in temporal bone using U-HRCT comparing it to ConvCT. MATERIALS AND METHODS: A total of 30 patients (14 males and 16 females; age range, 8-82 years; median 49 years) underwent both U-HRCT and ConvCT. All CT images were obtained with 0.5 mm section thickness and a 512 × 512 matrix, and field of view of 80 mm. Transverse scans were acquired in a plane parallel to the orbitomeatal plane in the helical mode with 120 kV. Images of the 30 temporal bones of unaffected side were reviewed by two independent neuroradiologists who rated the visibility of key anatomic structures for both U-HRCT and ConvCT. The ratings between U-HRCT and ConvCT were compared using Wilcoxon matched-pairs signed rank test. The interobserver agreement on the rating of stapedius tendon was evaluated using weighted κ statistics. RESULTS: Excellent interobserver agreement was shown for U-HRCT (κ = 0.920), whereas good agreement was obtained for ConvCT (κ = 0.733). According to both observers, stapedius tendon was more clearly visualized using U-HRCT than ConvCT (p < 0.0001). All other anatomic structures were well visualized using both CT scanners. CONCLUSION: The anatomy of temporal bone is more conspicuous on U-HRCT than on ConvCT because of its ultra-high-resolution detector. U-HRCT may provide beneficial information for determining surgical indication or procedures.

Diagnosis and following up of Ménière's disease using multifrequency tympanometry-Cutoff values and temporal changes in measurements.

OBJECTIVE: This study aimed to verify cutoff values for G width (the width of bimodal peaks for the waveform obtained when measuring conductance at 2000Hz) in Japanese individuals diagnosed with Ménière's disease (MD) using multifrequency tympanometry (MFT) and to determine the relationship between the G width and ability to hear low-pitched sounds using measurements over time. METHODS: The study included 51 patients with clinically diagnosed MD, who had not undergone endolymphatic sac surgery, but had no other known ear disease (57 ears in patients aged 22-80 years were affected, and 45 ears in patients aged 18-83 years were unaffected; mean age: 53.3±16.9 years). We also enlisted 80 healthy controls with no prior history of ear disease (160 ears, aged 22-76 years, mean age: 40.8±15.7 years). MFT was used to measure the bimodal peak width of the waveform obtained when measuring conductance at resonance frequency of 2000Hz. For patients who had G width measured several times over multiple outpatient visits, we used initial test data to analyze cutoff values. In nine cases with four or more measurements over time, we evaluated a possible correlation between G width and the sum of the hearing threshold for three low-pitched frequencies (125Hz, 250Hz, and 500Hz). We used Student's t-test to determine significance. RESULTS: The both ears in the MD patients had a G width wider than the distribution in the control group. There was a significant difference between G width in the control group and in affected ears with MD (p=0.00026) and there was also a significant difference between G width in the control group and in unaffected ears of MD patients (p=0.0056). The cutoff value set with a specificity of 95% was 200daPa, with a sensitivity of 35.1% and specificity of 95.6%. The cutoff value set with a sensitivity of 50% was 140daPa, with sensitivity of 50.9% and specificity of 78.8%. There was no significant difference between resonance frequency of ears in the control group and ears with MD (p=0.41). In nine cases with four or more measurements over time, a case showed a statistically significant positive correlation between the G width and hearing ability threshold for low-pitched sounds (125Hz, 250Hz, and 500Hz) (p=0.03), while an another case showed a tendency toward a positive correlation, which was not statistically significant (p=0.08). Further, there were cases that did not show significant differences in the present study, but might have shown a negative correlation if the number of measurements had been increased. CONCLUSION: Measurement of G width using MFT may have accuracy as the traditional endolymphatic hydrops test. MFT is non-invasive, causes little discomfort for patients, requires little time to perform, and can be performed by paramedics. MFT was shown to be useful in screening for MD and it is effective in diagnosing MD to measure the change over time of G width using MFT.

Preoperative simulation unveiled undetected surgical difficulties in a case of cochlear implantation.

We herein report a case in which extensive preparation changed a difficult-to-treat patient into an easy one. We performed a revision cochlear implantation on a patient whose first procedure had been aborted due to unidentified difficulties. During a series of thorough three-dimensional simulations, we found that the patient in question had a normal cochlea but the cochlea was placed in an unusual position and orientation. This condition is difficult to detect on standard preoperative radiographic images. Through this simulation, we were able to propose a surgical plan to avoid making the same mistakes as the first surgeon. We present this case not as a rare difficult case of an unfortunate patient but instead emphasise the importance of performing surgical simulation and looking for non-obvious difficulties. This case is an example of the success that can be achieved with such extensive preparation.

The accuracy of an electromagnetic navigation system in lateral skull base approaches.

OBJECTIVES/HYPOTHESIS: Image-guided optical tracking systems are being used with increased frequency in lateral skull base surgery. Recently, electromagnetic tracking systems have become available for use in this region. However, the clinical accuracy of the electromagnetic tracking system has not been examined in lateral skull base surgery. This study evaluates the accuracy of electromagnetic navigation in lateral skull base surgery. STUDY DESIGN: Cadaveric and radiographic study. METHODS: Twenty cadaveric temporal bones were dissected in a surgical setting under a commercially available, electromagnetic surgical navigation system. The target registration error (TRE) was measured at 28 surgical landmarks during and after performing the standard translabyrinthine and middle cranial fossa surgical approaches to the internal acoustic canal. In addition, three demonstrative procedures that necessitate navigation with high accuracy were performed; that is, canalostomy of the superior semicircular canal from the middle cranial fossa,1 cochleostomy from the middle cranial fossa,2 and infralabyrinthine approach to the petrous apex.3 RESULTS: Eleven of 17 (65%) of the targets in the translabyrinthine approach and five of 11 (45%) of the targets in the middle fossa approach could be identified in the navigation system with TRE of less than 0.5 mm. Three accuracy-dependent procedures were completed without anatomical injury of important anatomical structures. CONCLUSION: The electromagnetic navigation system had sufficient accuracy to be used in the surgical setting. It was possible to perform complex procedures in the lateral skull base under the guidance of the electromagnetically tracked navigation system. LEVELS OF EVIDENCE: N/A. Laryngoscope, 2016 127:450-459, 2017.

Registration using 3D-printed rigid templates outperforms manually scanned surface matching in image-guided temporal bone surgery.

PURPOSE: Image-guided surgery (IGS) for otological procedures requires minimal invasiveness and a high degree of accuracy. We have recently developed a noninvasive registration method, the Surface Template-Assisted Marker Positioning (STAMP) method, which uses a rigid template of the surface of the temporal bone. However, the STAMP method is not applicable when the bony surface is not exposed, such as in endoscopic surgery. Thus, we extended our research to apply the STAMP method onto the skin and tested its feasibility in this study. METHODS: We designed a phantom made of a rigid box and soft material for the study. The target registration error (TRE) was measured at preset measuring points in the phantom. We modified the STAMP method to be applicable for use on the skin around the ears (S-STAMP). The same phantom was also registered using the conventional, manually scanned surface matching method. We compared the TRE after the different registration methods. RESULTS: The TRE after the S-STAMP registration method was significantly smaller than that of the conventional surface matching method at all error measurement points in the phantom. However, the TRE after the S-STAMP registration method was significantly larger than that of paired point registration using invasive fiducial markers. CONCLUSIONS: The S-STAMP method using a rigid template on the soft surface yields a significantly smaller TRE than that of conventional, manually scanned surface matching registration. This strategy provides an alternative option to improve the accuracy of IGS without loading patients with additional invasive procedures.

Semi-manual mastoidectomy assisted by human-robot collaborative control - A temporal bone replica study.

OBJECTIVE: To develop an otological robot that can protect important organs from being injured. METHODS: We developed a five degree-of-freedom robot for otological surgery. Unlike the other robots that were reported previously, our robot does not replace surgeon's procedures, but instead utilizes human-robot collaborative control. The robot basically releases all of the actuators so that the surgeon can manipulate the drill within the robot's working area with minimal restriction. When the drill reaches a forbidden area, the surgeon feels as if the drill hits a wall. RESULTS: When an engineer performed mastoidectomy using the robot for assistance, the facial nerve in the segmented region was always protected with a more than 2.5mm margin, which was almost the same as the pre-set safety margin of 3mm. CONCLUSION: Semi-manual drilling using human-robot collaborative control was feasible, and may hold a realistic prospect of clinical use in the near future.

Primary leiomyosarcoma of the colon.

Primary leiomyosarcomas of the gastrointestinal (GI) tract are extremely rare and highly aggressive neoplasms, and only a small number of true cases have been reported since the concept of GI stromal tumors was established. Here, we report a case of a primary leiomyosarcoma of the transverse colon. A 46-year-old Japanese male with a large mass in the right upper abdomen was admitted to our hospital. Computed tomography and magnetic resonance imaging revealed long segments of wall thickening of the transverse colon with large consecutive tumors measuring 12 cm in diameter. A projecting irregular mass with marked mucosal necrosis was found on colonoscopy. Pathological examination revealed a spindle cell tumor growing circumferentially and transmurally to replace the muscularis propria in the transverse colon. The spindle cells were positive for smooth muscle actin, and negative for KIT, CD34, DOG-1, and S-100 protein. The patient has shown repeat recurrence in spite of sufficient surgical excision being promptly performed.