Local Recurrence After Transanal Endoscopic Microsurgery for Rectal Polyps and Early Cancers

Background Transanal endoscopic microsurgery (TEM) allows for local excision of rectal neoplasms with greater exposure than transanal excision and less morbidity than transabdominal approaches. This study examines the implications of the procedure with respect to predictors of recurrence. Methods We performed a retrospective analysis of 144 consecutive TEMs from 1993 to 2004. Results The study comprises 107 patients presenting for TEM with benign disease and 32 patients with cancer. Patients had a mean age of 64 ± 14 (SD) years. TEM was performed for recurrent lesions in 17% of cases. Pathologic classification of the lesions after TEM was benign adenoma in 45%, adenoma with high-grade dysplasia (HGD) in 17%, cancer in 33%, and other in 4%. Complications occurred in 10%, and local recurrence occurred in 15% of patients. Median follow-up was 44 months, with a median time to recurrence of 14 months. Positive margins did not influence lesion recurrence. Recurrence of cancers correlated with the depth of tumor invasion (P < .05). On multivariate analysis, independent predictors of recurrence were lesion size and the presence of HGD within adenomas (P < .05). Five-year neoplastic recurrence probabilities were 11% for benign adenomas, 35% for adenomas with HGD, and 20% for cancers (P = .31); invasive recurrence probabilities were 0% for benign adenomas, 15% for adenomas with HGD, and 13% for cancers (P < .05). Conclusions Close endoscopic follow-up is warranted after TEM for both benign and malignant disease, with special attention to lesions with HGD. TEM can be performed safely for early rectal cancer with careful patient selection. Presented at the Society of Surgical Oncology, 58th Annual Cancer Symposium, Atlanta, Georgia, March 3–6, 2005.     

经肛门内镜微创手术与传统经肛门局切术治疗早期直肠肿瘤的疗效对比

目的 对比经肛门内镜微创手术(TEM)与传统经肛门局切术(TAE)治疗早期直肠肿瘤的应用指征、安全性、疗效.方法 回顾性分析上海交通大学医学院附属瑞金医院普外科2003年1月- 2006年7月完成的76例传统经肛门局切术及2006年9月- 2010年2月完成的53例经肛门内镜微创手术的临床资料.结果 两组患者性别、年龄...     

Transanal endoscopic microsurgery for rectal carcinoids: the largest reported United States experience

Aim Rectal carcinoids are often inadequately resected by snare excision during colonoscopy. Transanal endoscopic microsurgery is a minimally invasive procedure with low morbidity that offers full‐thickness excision with a low rate of negative margins. It presents an excellent alternative to radical surgery for mid and proximally located lesions. We report the largest United States (US) experience in the use of transanal endoscopic microsurgery for rectal carcinoids. Method Data of patients who had undergone transanal endoscopic microsurgery for rectal carcinoids were prospectively collected and retrospectively analyzed. Patient and tumour characteristics, operative and perioperative details, as well as oncological outcomes were reviewed. Results Over a 12‐year period, 24 patients underwent transanal endoscopic microsurgery for rectal carcinoids. Of these, six (25%) were primary surgical resections and 18 (75%) were performed after incomplete snare excisions during colonoscopy. Three (17%) patients who underwent full‐thickness resection after snare excision had residual tumour on histopathological examination. Negative margins were obtained in all cases. No recurrences were noted. Conclusion Transanal endoscopic microsurgery is effective and safe for the surgical resection of rectal carcinoids < 2 cm in diameter, with typical features and located more than 5 cm from the anal verge. Transanal endoscopic microsurgery can be used for primary resection or for resection after incomplete colonoscopic snare excision.     

Transanal endoscopic excision of rectal adenomas

Transanal endoscopic microsurgery (TEM) is a minimally invasive surgical technique for performing local excision of rectal lesions in the mid and upper rectum that would otherwise be inaccessible for local excision by the direct transanal approach. In the absence of this approach, low anterior resection would be required, which is major abdominal surgery. The justification for excising adenomas of the colon and rectum is their malignant potential, which correlates with the size of the lesion. This retrospective review examines our experience using TEM for excision of adenomas of the rectum from February 1991 to the present. The decision for using TEM is based on a precise localization of the lesion with particular attention to the upper margin of the lesion and its diameter. A total of 56 adenomas were removed. The average diameter was 4.9 cm (range, 3–8 cm). The average distance from the anal verge was 7.92 cm (range, 5–12 cm). Carcinoma in situ was seen in 7 lesions, and the remaining lesions were benign. Morbidity was minimal, with one conversion to an open procedure for an intraperitoneal perforation that required a low anterior resection. No patient required transfusion and there was no mortality. The hospital stay was short, with half of the patients being discharged the same day. The average cost from July 1996 to December 1999 was $7775 for TEM versus $34,018 for LAR. Subsequent follow-up average was 38.8 months (range, 1–100 months), during which time two patients had recurrence of their adenomas. This was successfully treated with reexcision. In conclusion, TEM is an accurate, safe, and relatively inexpensive technique when compared to low anterior resection. This technique significantly reduces the proportion of adenomas requiring abdominal surgery.     

Comparison of results after transanal endoscopic microsurgery and radical resection for T1 carcinoma of the rectum

Background: We compared the results of transanal endoscopic microsurgery and radical surgery in patients with T1 carcinomas of the rectum. Methods: We performed a retrospective study (1985–96) to compare the results obtained in 103 patients with T1 rectal carcinomas (low-risk T1, n= 80; high-risk T1; n= 23) undergoing transanal endoscopic microsurgery and radical surgical therapy. Results: The complication rate in patients undergoing local excision was 3.4% (two of 58); it was 18% (eight of 45) in the group treated with radical surgery. Two of 45 patients (3.8%) died after radical resection; there were no deaths after local excision. With regard to the actuarial 5-year survival rate, no difference was observed in the group with low-risk T1 carcinoma between patients treated with local excision (79%) and those who had radical resection (81%) (p= 0.72). In patients with high-risk T1 carcinoma, lymph node metastases were identified in four of 11 patients undergoing radical resection (36%). Four of 12 patients with high-risk T1 carcinoma treated by local excision developed recurrences, whereas none of the patients undergoing primary radical surgery had a recurrence. Conclusions: Transanal endoscopic microsurgery for the treatment of low-risk T1 carcinomas is associated with a significantly lower complication rate than radical surgical therapy. There is no difference in 5-year survival between local and radical surgical therapy in patients with low-risk T1 carcinoma. Received: 23 May 1997/Accepted: 18 December 1997     

Who should be followed up after transanal endoscopic resection of rectal tumours?

Objective To determine follow‐up requirements following transanal endoscopic microsurgery (TEM) for rectal tumours based on clinical and histopathological assessment of resection specimens. Method A consecutive series of 117 patients undergoing TEM between 1997 and 2005 was studied. The excised specimens were classified as intact with clear surgical resection margins, macroscopically intact specimens with microscopically involved resection margins or piecemeal. Recurrence rates were determined for the three groups. Results Of the 117 procedures performed, 80 were for benign disease and 37 for malignancy. Within the benign group 39 (49%) resections were intact with clear surgical resection margins and yielded zero recurrences; 22 (27%) resections were macroscopically intact with microscopically involved surgical resection margin and yielded two recurrences; and 19 (24%) resections were piecemeal and yielded eight recurrences. Within the malignant group all 37 patients had resection specimens which were intact with clear surgical resection margins. Two patients had immediate salvage surgery. Of the 35 who went on to long‐term follow‐up post‐TEM (0.6–8.1 years, median 4) four developed recurrent cancer (two local with submucosal disease and two liver metastases). Conclusion For benign rectal neoplasms, resection of an intact specimen with histologically clear surgical resection margins was associated with no observed mucosal recurrence. Local recurrence after TEM is significantly more frequent when histological examination reveals involved margins or when resection is piecemeal. Early endoscopic follow up is required for the latter two groups. Local recurrence for malignant cases was submucosal and detected by palpation.     

Harmonic long shears further reduce operation time in transanal endoscopic microsurgery

Background  Previous research indicates that application of 5-mm harmonic shears rather than diathermia significantly reduces operation time in transanal endoscopic microsurgery (TEM). Frequently, however, additional instruments were required to complete resection. We investigated whether the new 5-mm harmonic long shears (H-LS) are better equipped for TEM compared with regular harmonic shears (HS). Methods  Between 2001 and 2006, 162 tumors (117 adenomas, 42 carcinomas, and 3 other tumors; mean distance 6.6 cm, mean area 40 cm²) were excised in 161 patients (82 men, 79 women; mean age 66 years). Results  Eighty-eight resections were performed with HS and 74 with H-LS. Tumor and patient characteristics were similar except for specimen area. Tumors resected by H-LS were on average smaller than those resected by HS (34.4 versus 44.1 cm²; Mann–Whitney U-test: p = 0.027). Mean operation time was 48 min and proportional to area in both groups (univariate analysis of variance p < 0.001). Mean operation time was 54 min using HS and 41 min using H-LS (t-test: p < 0.001). After correction for area, operation time for H-LS was reduced by 14% compared with HS (t-test: p < 0.001). H-LS is singly capable of completing resection in 88% compared with 26% for HS (Mann–Whitney U-test: p < 0.001). Mean blood loss was 16 cc for HS and 3 cc for H-LS (p < 0.001). Morbidity (11%) and mortality (0.6%) were not different between the two groups (Fisher’s exact test). Conclusion  Performing transanal endoscopic microsurgery with 5-mm harmonic long shears reduces operation time compared with regular shears, and completing resection seldom requires other instruments. Presented orally at the 15th International Congress at the European Association of Endoscopic Surgery in Athena, Greece, July 5th 2007.     

Transanal endoscopic microsurgery in the treatment of rectal carcinoid tumor

Background This study aimed to assess the efficacy of transanal endoscopic microsurgery (TEM) in the treatment of rectal carcinoid tumor. Methods Between May 1994 and April 2006, 27 patients with rectal carcinoid tumor underwent TEM, and their clinical data were reviewed retrospectively. Results The TEM procedure was performed as a primary excision (n = 14) or as completion surgery after incomplete resection by endoscopic polypectomy (n = 13). The average size of a primary tumor was 9.1 mm (range, 5–13 mm), and the average distance of the tumor from the anal verge was 8.5 cm. The mean duration of the operation was 51.6 min. Minor morbidities, transient soilage, and mild dehiscence occurred in two cases (7.4%). Histopathologically, all tumors were localized within the submucosal layer showing typical histology without lymphatic or vessel infiltration, and both deep and lateral surgical margins were completely free of tumors. Among 13 cases of completion surgery after endoscopic polypectomy, 4 (30.8%) were histologically shown to have a residual tumor in the specimens obtained by TEM. No additional radical surgery was performed. The mean follow-up period was 70.6 months, and no recurrence was noted. Conclusion The results indicate that TEM is a safe, minimally invasive procedure for the local excision of rectal carcinoid tumors, particularly those in the proximal rectum. Furthermore, for patients with microscopic positive margins after endoscopic polypectomy, TEM can be an effective surgical option for complete removal of residual tumors.     

经肛手套通路联合结肠镜微创手术治疗直肠肿瘤

目的：探讨经肛手套通路联合结肠镜微创手术治疗直肠肿瘤的可行性及疗效。方法杭州市第三人民医院肛肠外科自2012年10月至2013年3月,选择经评估适合行局部切除的直肠肿瘤患者8例,使用经肛手套通路联合结肠镜微创手术治疗。经肛手套通路的建立：将手套袖口连同扩肛器缝合固定于肛周,再将手套5指经由透明肛门镜翻转出肛门,将超声刀、无损伤肠钳和肠镜镜头分别从3个指套伸入并结扎固定。结果8例患者均成功完成肿瘤切除手术,制作手套入路装置平均耗时12．5（10．0～15．0） min,平均手术时间55．6（30．0～110．0） min,平均住院时间为5．0（3．0～8．0） d,术后病理提示绒毛状腺瘤3例,管状腺瘤2瘤,管状绒毛状腺瘤2例,锯齿状腺瘤1例,其中2例伴低级别上皮内瘤变,1例高级别上皮内瘤变,所有肿瘤组织标本边缘及基底部均为阴性。术后2例患者少量便血,随访1～5（中位3．1）月,无肿瘤复发。结论采用经肛手套通路联合结肠镜微创手术治疗直肠早期肿瘤具有简单和安全的特点,具有一定的应用价值。     

Transanal endoscopic microsurgery for rectal tumors: the St. Mary's experience

BACKGROUND: The aim of this study is to describe a single institution's experience in the use of transanal endoscopic microsurgery for rectal tumors. METHODS: Between 1996 and 2005, transanal endoscopic microsurgery was performed in 76 patients. The histologic diagnosis was adenoma in 48 and adenocarcinoma in 28 patients. RESULTS: Clear resection margins were achieved in 71 of 74 patients (95.9%). Overall morbidity was 18.9% because 14 patients developed minor (10 patients) or major complications (4 patients). During the follow-up, benign tumor recurrence was detected in 3 patients (6.3%). The recurrence rates among patients with T1, T2, and T3 malignant tumors were 7.1%, 42.8%, and 66.6%, respectively. COMMENTS: Transanal endoscopic microsurgery is a safe and feasible technique with low incomplete excision rates and may be the preferred method in patients with benign rectal tumors. Its role in the management of malignant tumors should be limited to selected patients with T1 lesions.     

Endoscopic mucosal resection vs transanal endoscopic microsurgery for the treatment of large rectal adenomas

Aim Large (> 2 cm) rectal adenomas are currently treated by transanal endoscopic microsurgery (TEM) or piecemeal endoscopic mucosal resection (EMR). The potential lower morbidity of EMR becomes irrelevant if it is less effective. We aimed to compare the safety and effectiveness of EMR and TEM for large rectal adenomas. Method Data from patients undergoing TEM or EMR for a rectal adenoma > 2 cm in eight hospitals were retrospectively collected. Patient‐ and procedure‐related characteristics, complications and recurrences were recorded. As EMR may require several attempts to achieve complete resection, early (after a single intervention) and late (permitting re‐treatment for residual adenoma within 6 months) recurrence rates were determined. Results Two hundred and ninety‐two (292) patients (49% male; mean age 67 years) were included; 219 were treated by TEM and 73 by EMR. Adenomas treated by EMR were smaller (median 30 vs 40 mm; P = 0.007). Perioperative complication rates were 2% for TEM and 6% for EMR (P = 0.171). Postoperative complications occurred in 24% of TEM patients and in 13% of EMR patients (P = 0.038). Median hospitalization after TEM was 3 days vs 0 days after EMR (P < 0.001). Median follow‐up was 12.6 months (0–47 months); Early recurrence rates were 10.2% in TEM patients and 31.0% in EMR patients (P < 0.001); late recurrence rates were 9.6% and 13.8%, respectively (P = 0.386). Conclusion After a single intervention, EMR of large rectal adenomas seems less effective, but safer than TEM. When allowing re‐treatment of residual adenoma within 6 months, EMR and TEM seem equally effective. A prospective randomized comparison seems to be necessary.     

Is transanal endoscopic microsurgery (TEM) a valid treatment for rectal tumors?

Background: In 1983 G. Buess, in Germany, developed transanal endoscopic microsurgery (TEM), a new minimally invasive technique for the treatment of rectal tumors. Methods: Rectal lesions are excised through a modified rectoscope of 40 mm in diameter under stereoscopic control in the gas-dilated rectal cavity. Full-thickness excision, partialwall excision, or mucosectomy can be performed. Seventy-one patients were treated with the TEM technique in our department. Major complications were observed in one patient (1.4%). No mortality was reported. Results: Histological examination revealed 40 (56.3%) villous adenomas, 6 (8.4%) pT1; 17 (23.9%) pT2; 5 (7%) pT3 carcinomas; and 3 (4.2%) other lesions. The recurrence rate was 2.8% for adenomas and 2.8% for carcinomas. The overall survival at mean follow-up of 17 months was 96.4%. Conclusions: The advantages of TEM are less or no post-operative pain, unrestricted mobility, short hospitalization, quick rehabilitation, and absence of skin scars.Selected for the Free papers session for EAES awards at the Third International Congress on New Technology and Advanced Techniques in Surgery, Luxembourg, June 13–17, 1995     

Local Rectal Tumor Resection Results: Gasless,Video-endoscopic Transanal Excision versus the Conventional Posterior Approach

Abstract This study compares surgical outcomes for local resection of rectal tumors by two approaches: (1) gasless, video-endoscopic transanal-rectal tumor excision (gasless VTEM); and (2) a conventional posterior approach. Gasless VTEM involves a modification of transanal endoscopic microsurgery (TEM) that incorporates a standard laparoscopic video camera without a CO₂ insufflation system. A series of 42 patients with 45 rectal tumors (9 adenomas, 36 adenocarcinomas) who underwent gasless VTEM between 1993 and 2000 were studied prospectively. The control group consisted of 26 similar patients who underwent conventional surgery (transsacral or transsphincteric approach) between 1985 and 1993. Age, gender ratio, tumor localization, maximum tumor diameter, and histology for the cases and the controls were similar, whereas operating time and blood loss were significantly greater in the control group (p < 0.001 and p < 0.001, respectively). The postoperative intervals until able to walk, urinary catheter removal, solid food intake, and discharge from hospital were significantly shorter in the gasless VTEM group (p < 0.001, p = 0.002, p < 0.001, and p < 0.001, respectively); analgesic requirements were significantly less (p < 0.001). There was no operative mortality in either group. Postoperative complications developed significantly less frequently in the gasless VTEM group than in the control group (7.1% vs. 38.5%; p = 0.003). During the median follow-up length of 73.3 months, no patient developed tumor recurrence in the gasless VTEM group, whereas one patient did in the control group. In conclusion, gasless VTEM is less invasive and allows shorter hospitalizations and reduced complications than the conventional posterior approach, thereby providing an attractive alternative for selected patients.     

Recurrence after transanal endoscopic microsurgery for large rectal adenomas

Background

Transanal endoscopic microsurgery (TEM) has revolutionized the technique and outcome of transanal surgery, becoming the standard of treatment for large sessile rectal adenomas. Nevertheless, only a few studies have evaluated the risk factors for local recurrence in order to recommend a “tailored” approach. The aim of this study was to identify predictor variables for recurrence after TEM to treat rectal adenoma.

Methods

This study is a retrospective analysis of a prospective database of patients treated for large sessile rectal adenomas by TEM at our institution, with a minimum follow-up of 12?months. Age, gender, tumor diameter, distance from the anal verge, degree of dysplasia, histology, and margin involvement were investigated.

Results

Between January 1993 and July 2010, 293 patients with a rectal adenoma ≥3?cm underwent TEM. Postoperative morbidity rate was 7.2?% (21/293) and there was no 30-day mortality. Over a median follow-up period of 110 (range?=?12–216) months, 13 patients (5.6?%) were diagnosed with local recurrence. The median time to recurrence was 10 (range?=?4–33) months, with 76.9?% of recurrences detected within 12?months after TEM. At univariate analysis, tumor diameter (p?=?0.007), and positive margins (p?p?=?0.003).

Conclusions

TEM provides excellent oncological outcomes in the treatment of large sessile benign rectal lesions, assuring a minimal risk of resection margin infiltration at pathology examination, which represents the only risk factor for recurrence.     

Transanal resection using a single port trocar: a new approach to NOTES

Introduction

The morbidity and mortality, along with the functional changes that arise from radical surgery of rectal cancer, has led to an increasing interest in local treatment in the early stages of cancer of the rectum. Conventional transanal surgery has a high recurrence rate, for this reason transanal endoscopic microsurgery (TEM) is considered the treatment of choice in the last few years in large rectal adenomas and in early rectal cancer (low risk T1).

Patients and method

We have intervened five patients, four with a diagnosis of villous adenoma of the rectum, and one in situ rectal carcinoma, using this new transanal approach, with a single port device.

Results

The locations of the lesions were in the mid-rectum, at a mean distance of 9 cm (range 6-10) from the anal margin. All of them were situated in the posterior side. The resection margins were negative in all cases. The mean size of the adenomas was 4 cm, three being sessile shaped, and one with a short, thick pedicle (>1 cm); the size of the carcinoma was 3 cm. The mean surgical time was 55 minutes. All the patients were discharged 48 hours after the surgical procedure.

Conclusion

We believe that the transanal endoscopic approach with a single port device is a simple, easily reproducible and cost-effective procedure when compared to TEM.     

Factors predicting early recurrence after transanal endoscopic microsurgery excision for rectal adenoma

INTRODUCTION: Transanal endoscopic microsurgery (TEM) is an accepted way of excising rectal adenomas with low morbidity and mortality, avoiding major resectional surgery. However, there are no agreed criteria for surveillance following TEM. The purpose of this study was to identify criteria to guide surveillance programmes, thus reducing the surveillance burden for those patients at low risk of recurrence. PATIENTS AND METHODS: Patients who had undergone TEM for rectal adenomas were identified, and a retrospective review of patient, pathological and histological parameters was performed. RESULTS: Seventy-five (40 male) patients were identified; median age 70 years (39-85). There were seven tubular, 33 tubulo-villous and 35 villous adenomas. All were considered completely excised by the operating surgeon. Forty-seven (62.7%) were reported as being completely excised histologically. There was no significant association between recurrence at 6 months and sex, age, type or position of adenoma, height above the anal verge, or degree of dysplasia. Recurrence rates at six months were 0% for the completely excised adenomas and 21.4% for the incompletely excised ones; this was statistically significant (Pearson chi(2), P < 0.001). In all there were 12 recurrences, 10 in the incompletely excised group at a median follow up of 31 (6-80) months (P < 0.001). In addition, a significant association for large adenomas to recur was noted at median follow up (Armitage Trend test, P = 0.019). CONCLUSIONS: Histological assessment of completeness of excision of rectal adenoma and size of adenoma are important predictors of early recurrence and have potential to guide follow-up strategies after TEM.     

Initial Experience with Transanal Endoscopic Microsurgery: the Need for Understanding the Limitations

Introduction  

Transanal endoscopic microsurgery is an alternative to transanal excision or radical surgery for benign and carefully selected malignant rectal tumors. Advantages over transanal excision include better visualization, access to more proximal lesions, higher likelihood of negative margins, and lower recurrence rates. Compared to radical resection, patients experience lower rates of morbidity and mortality but may have higher rates of local recurrence.     

Transanal endoscopic microsurgery: a review

Rectal adenomas and cancers occur frequently. Small adenomas can be removed colonoscopically, whereas larger polyps are removed via conventional transanal excision. Owing to technical difficulties, adenomas of the mid- and upper rectum require radical resection. Transanal endoscopic microsurgery (TEM) was first designed as an alternative treatment for these lesions. However, since its development TEM has been also used for a variety of rectal lesions, including carcinoids, rectal prolapse and diverticula, early stage carcinomas and palliative resection of rectal cancers. The objective of this review is to describe the current status of TEM in the treatment of rectal lesions. Since the 1980s, TEM has advanced substantially. With low recurrence rates, it is the method of choice for resection of endoscopically unresectable adenomas. Some studies have shown benefits to its use in treating early T1 rectal cancers compared with radical surgery in select patients. However, for more advanced rectal cancers TEM should be considered palliative or experimental. This technique has also been shown to be safe for the treatment of other uncommon rectal tumours, such as carcinoids. Transanal endoscopic microsurgery may allow for new strategies in the treatment of rectal pathology where technical limitations of transanal techniques have limited endoluminal surgical innovations.     

Transanal endoscopic microsurgery for 135 patients with small nonadvanced low rectal cancer (iT1�CiT2, iN0): short- and long-term results

Background  

Local excision of rectal cancer as an alternative to radical resection for patients with small nonadvanced low rectal cancer (SNALRC) (iT1–iT2, iN0) is debated. This study aimed to analyze the short- and long-term results for a series of 135 patients with SNALRC who underwent local excision by transanal endoscopic microsurgery (TEM).     

Follow-up after transanal endoscopic microsurgery or transanal excision of large benign rectal polyps

Methods: Between January 1986 and December 1995, 238 patients with benign rectal polyps under-went either transanal endoscopic microsurgery (n = 226) or transanal excision (n = 12) at the Clinic of General and Abdominal Surgery, Johannes Gutenberg-University, Mainz. Results: Mean polyp size was 4.2 cm; 89.1% of polyps measured more than 2 cm in diameter. In 89.1% of cases, histological analysis revealed polyps containing tubulovillous or villous adenomas. Synchronous colonic polyps were detected in 12.5% of patients. Follow-up data are available on 222 patients (94%). At follow-up examination, 169 of the 193 surviving patients (87.6%) were recurrence free. Seven of 193 patients (3.6%) had developed neoplastic colonic polyps and, in 17 patients (8.8%), metachronous polyps were detected. Conclusions: Transanal endoscopic microsurgical polypectomy was furthermore demonstrated to be a low-risk procedure with a low recurrence rate for the complete resection of large rectal polyps. At a follow-up rate of 61.1%, the incidence of metachronous carcinoma ranged at 3.1%, which is markedly below the rate of 8–18% for tubulovillous or villous adenomas larger than 1 cm in diameter cited in the literature. Received: 24 October 1997 / Accepted: 13 July 1998