The topographical and age distributions of neuroendocrine cells in the normal human appendix

Current Management of Appendiceal Neoplasms

Appendiceal neoplasms include a heterogeneous group of epithelial and nonepithelial tumors that exhibit varying malignant potential. This review article summarizes current diagnostic criteria, classification systems, and optimal therapeutic strategies for the five main histopathologic subtypes of appendiceal neoplasms. In particular, the management of epithelial appendiceal neoplasms has evolved. Although their treatment has historically been extrapolated from colon cancer, improved understanding of their unique histopathologic and molecular characteristics and a growing body of published clinical data support a more nuanced approach to their management.

Appendiceal Neoplasms

Appendiceal neoplasms are identified in 0.9 to 1.4% of appendiceal specimens, and the incidence is increasing. It has long been professed that neuroendocrine tumors (formerly carcinoids) are the most common neoplastic process of the appendix; recent data, however, has suggested a shift in epidemiology. Our intent is to distill the complex into an algorithm, and, in doing so, enable the surgeon to seamlessly maneuver through operative decisions, treatment strategies, and patient counseling. The algorithm for evaluation and treatment is complex, often starts from the nonspecific presenting complaint of appendicitis, and relies heavily on often subtle histopathologic differences.

Pediatric neuroendocrine carcinoid tumors: Management, pathology, and imaging findings in a pediatric referral center

BACKGROUND

While neuroendocrine (carcinoid) tumors are increasingly recognized in the adult population, they are often not suspected in children.

PROCEDURE

Retrospective review of all well-differentiated neuroendocrine (carcinoid) tumors was performed based on pathology reports from a quaternary pediatric medical center between January 2003 and June 2016. Clinical presentations, treatment approaches, imaging findings, and outcomes were reviewed and analyzed.

RESULTS

A total of 45 cases of pathology-proven carcinoid tumor were reported with an average age of 14.1 years (range: 7-21 years, SD: 2.8 years). Of these cases, 80% (36) were appendiceal, 11% (5) bronchial, 2% (1) colonic, 2% (1) gastric, 2% (1) enteric, and 2% (1) testicular. Metastases were observed in one (3%) appendiceal, one (100%) enteric, and two (40%) bronchial cases. No recurrence was demonstrated in any appendiceal carcinoid cases. Recurrence was seen in one of three extra-appendiceal gastrointestinal tumors. Tumor site and size significantly correlated with metastases and recurrence.

CONCLUSIONS

Contrary to recent epidemiological investigations in adults, appendiceal carcinoid tumors remain the most common site for pediatric carcinoid tumors. Appendiceal carcinoid tumors exhibited benign clinical courses without recurrence during short-term follow-up. Extra-appendiceal gastrointestinal carcinoid tumors exhibited much more aggressive behavior with greater metastases and recurrence. Bronchial carcinoid tumors demonstrated good clinical response to resection even in cases with mediastinal lymph node involvement. While increased use of urine 5-HIAA levels and somatostatin receptor-specific imaging might improve detection and guide management of extra-appendiceal carcinoid tumors, longer-term follow-up is needed.

Does elevated urinary 5-hydroxyindole acetic acid level predict acute appendicitis in children?

BACKGROUND

Acute appendicitis is the most common abdominal surgical emergency in children, and appendectomy is the most frequent acute abdominal operation. Prompt diagnosis and surgical treatment are required to reduce the risk of perforation and prevent complications, especially in small children. Enterochromaffin cells that contain large amounts of serotonin are mostly located in the distal appendix. Serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) could therefore be a marker for acute appendicitis.

OBJECTIVE

We tested urinary 5-HIAA concentrations in spot urine samples from children with acute appendicitis.

METHODS

We enrolled 93 patients who underwent surgery for suspicion of acute appendicitis. The diagnosis was made intraoperatively and confirmed histopathologically. Additionally, urine samples from 102 healthy children were collected as controls. Their 5-HIAA was measured using high-performance liquid chromatography.

RESULTS

Acute appendicitis was diagnosed in 81 patients, whereas there were other explanations for abdominal pain in the remaining 12 patients in the non-appendicitis group. The control group comprised 102 healthy children. Considering the median of all measured 5-HIAA values as the cut-off, we analysed the proportions of patients with elevated values in all the groups. Our analysis showed that statistically there was no significant difference in the distribution of percentages among the groups. The area under the curve for 5-HIAA was 0.55 (95% CI 0.47 to 0.62) with sensitivity and specificity 60.4% and 48.9%, respectively.

CONCLUSIONS

Urine 5-HIAA concentration measured in spot samples is not a reliable method for diagnosing acute appendicitis in children.

Surgical Management of Neuroendocrine Tumors of the Appendix in Children and Adolescents: A Retrospective French Multicenter Study of 114 Cases

BACKGROUND

Right hemicolectomy (RHC) in patients with neuroendocrine tumors (NET) of the appendix has been advocated for tumors more than 2 cm, or with mesoappendix/vessel invasion, or with raised mitotic activity. No study demonstrated prolonged survival with RHC over appendectomy alone. The aim of this study was to contribute to define guidelines for secondary surgery in children or adolescents with NET of the appendix.

PROCEDURE

We contacted all French pediatric surgeons and oncologists by mail, and reviewed the records of patients under 18 with NET of the appendix from 1988 until 2012.

RESULTS

A total of 114 patients were recorded with a female/male ratio of 1.6. Median age at presentation was 12 years (range: 5-17 years). Ten patients had a tumor more than 2 cm. Twenty patients had evidence of extension into the mesoappendix, including five with blood or lymph vessels' invasion. Solely, one patient had a tumor with a high proliferative index. Incomplete resection was observed in three cases. Eighty-five patients had no criterion for secondary surgery. Twenty-nine patients had criteria for RHC but only 10 underwent surgery. None of the resected specimens showed carcinoid tumor. Three patients had positive lymph nodes. At the last follow-up, all patients were alive and disease free.

CONCLUSION

Appendectomy alone seems to be curative of these tumors with no influence on life expectancy. Follow-up is not only unnecessary, but its means, whether clinical, radiological or biological, are ineffective.

Appendiceal neuroendocrine neoplasms: diagnosis and management

Gastrointestinal neuroendocrine neoplasms (GI-NENs) are increasingly being recognised, while appendiceal NENs (aNENs) currently constitute the third most common GI-NEN. Appendiceal NENs are generally considered to follow an indolent course with the majority being localised at diagnosis. Thus, the initial surgical approach is not that of a planned oncological resection. Due to the localised nature of the disease in the majority of cases, subsequent biochemical and radiological assessment are not routinely recommended. Histopathological criteria (size, mesoappendiceal invasion, Ki-67 proliferation index, neuro- and angio-invasion) are mainly used to identify those patients who are also candidates for a right hemicolectomy. Goblet cell carcinoids are a distinct entity and should be treated as adenocarcinomas. Despite the absence of any substantial prospective data regarding optimal management and follow-up, recent consensus statements and guidelines have been published. The purpose of this review is to overview the published studies on the diagnosis and management of appendiceal NENs and to suggest a possible management protocol.

Incidental Appendiceal Carcinoids: Is Surgery Affecting Their Incidence?

Background

There is lack of consensus on the incidence of appendiceal carcinoids in recent times. The influence of number of appendicectomies performed has been postulated to play a role in this. To determine the incidence and clinico-pathological profile of appendiceal carcinoids in a cohort of patients undergoing emergency appendicectomies for clinically suspected acute appendicitis, and examine the influence of the trend (if any) of the number of appendicectomies performed on the overall incidence of appendiceal carcinoids.

Methods

A retrospective analysis of patients diagnosed with appendiceal carcinoids following presentation with acute appendicitis to the Modbury hospital, South Australia from March 2007 to April 2011. The patient cohort was divided into Group 1 (March 2007 - March 2009) and group 2 (April 2009 - April 2011) to study the influence of time trends on incidence of appendiceal carcinoids. Statistical analyses were performed using the Statistical Product and Service Solutions, SPSS 14.0 for Windows.

Results

Of 506 patients who underwent emergency appendicectomy for acute appendicitis, 8 patients (1.6%) were found to have appendiceal carcinoids. The median age was 23 years with 7 patients being female. There was no difference in the incidence of appendiceal carcinoids over the two time periods (P < 0.12).

Conclusions

Appendiceal carcinoids were found in 1.6% of patients undergoing emergency appendicectomy for acute appendicitis. These tumors are found more commonly in young females with a predilection for the tip of the appendix. The perceived increased incidence appendiceal carcinoids appear to be unrelated to the increase in the number of appendicectomies being performed.

[Surgical strategies for accidental detection of appendix carcinoids]

Carcinoids (neuroendocrine tumors NET) of the appendix are rare tumors and even today mostly detected only postoperatively by histopathology following operations for acute appendicitis or other abdominal procedures. Most NETs of the appendix are located at the tip of the appendix, less than 2 cm in size and non-metastasizing. Secondary right hemicolectomy with lymph node dissection bears a considerable risk of complications compared to simple appendectomy. To decide upon secondary surgery histopathological risk factors, such as grading, invasion of the mesoappendix, and tumor type in addition to tumor localization and size should be taken into consideration. Up to 20% of NETs of the appendix are associated with various neoplasms of the gastrointestinal tract. Follow-up examination should therefore also consider both appendix carcinoids and synchronous or metachronous neoplasms of the gastrointestinal tract.

Clinical Presentation and Management of Carcinoid Tumors

The generally indolent nature of neuroendocrine tumors is an advantage in the management of patients who have localized disease, and surgery alone is often curative. This same property presents a challenge in the treatment of patients who have metastatic disease, in whom standard cytotoxic chemotherapy has a limited benefit. In such patients, the use of somatostatin analogs, interferon, and the treatment of hepatic metastases may provide effective palliation. The highly vascular nature of carcinoid tumors has led to the investigation of antiangiogenic agents in this setting. Preliminary reports of activity associated with agents targeting the vascular endothelial growth factor pathway suggest that such strategies may play a role in the future treatment of patients who have this disease.

Neuroendocrine tumours (carcinoids) of the appendix

Neuroendocrine tumours (NETs) of the appendix (formerly 'carcinoids') are rare and are usually detected incidentally after appendectomy. Histopathologically they derive from a subepithelial cell population, which is different from NETs in other sites. They are preferentially located at the tip of the appendix. Tumours <1 cm hardly ever metastasize and are treated by appendectomy. Tumours >2 cm require right hemicolectomy because of a significant risk of metastatic spread. Treatment for lesions 1-2 cm is controversial and needs further characterization of the tumour (i.e. mesoappendiceal invasion, vascular invasion, mitotic activity, proliferation markers) and careful patient risk evaluation. Goblet-cell carcinoids have features resembling both carcinoid and adenocarcinoma and should be treated by hemicolectomy. Overall prognosis of small appendiceal NET is excellent in all ages.

Current status of gastrointestinal carcinoids

Gastrointestinal (GI) carcinoids are ill-understood, enigmatic malignancies, which, although slow growing compared with adenocarcinomas, can behave aggressively. Carcinoids are classified based on organ site and cell of origin and occur most frequently in the GI (67%) where they are most common in small intestine (25%), appendix (12%), and rectum (14%). Local manifestations--mass, bleeding, obstruction, or perforation--reflect invasion or tumor-induced fibrosis and often result in incidental detection at emergency surgery. Symptoms are protean (flushing, sweating, diarrhea, bronchospasm), usually misdiagnosed, and reflect secretion of diverse amines and peptides. Biochemical diagnosis is established by elevation of plasma chromogranin A (CgA), serotonin, or urinary 5-hydroxyindoleacetic acid (5-HIAA), while topographic localization is by Octreoscan, computerized axial tomography (CAT) scan, or endoscopy/ultrasound. Histological identification is confirmed by CgA and synaptophysin immunohistochemistry. Primary therapy is surgical excision to avert local manifestations and decrease hormone secretion. Hepatic metastases may be amenable to cytoreduction, radiofrequency ablation, embolization alone, or with cytotoxics. Hepatic transplantation may rarely be beneficial. Chemotherapy and radiotherapy have minimal efficacy and substantially decrease quality of life. Intravenously administered receptor-targeted radiolabeled somatostatin analogs are of use in disseminated disease. Local endoscopic excision for gastric (type I and II) and rectal carcinoids may be adequate. Somatostatin analogues provide the most effective symptomatic therapy, although interferon has some utility. Overall 5-year survival for carcinoids of the appendix is 98%, gastric (types I/II) is 81%, rectum is 87%, small intestinal is 60%, colonic carcinoids is 62%, and gastric type III/IV is 33%.

Does mesoappendix infiltration predict a worse prognosis in incidental neuroendocrine tumors of the appendix? A clinicopathologic and immunohistochemical study of 15 cases

We conducted a retrospective clinicopathologic and immunohistochemical study of the biologic significance of mesoappendix infiltration in 15 appendiceal neuroendocrine tumors selected from a series of 42 primary tumors. In all cases, the tumor was found incidentally and measured less than 2 cm (mean, 0.84 cm). In 13 cases, it was located in the tip of the appendix and in the midportion in 2. Histologically, none showed relationship with overlying mucosa. Necrosis was absent; mitotic figures were rare. The Ki-67 labeling index was low (1%-2%). In all cases, S-100 protein immunostaining disclosed positive elements with cytoplasmic dendritic processes closely intermingled with neuroendocrine neoplastic cells. All patients (8 males; 7 females; mean age, 38.2 years) underwent simple appendectomy. A right-sided hemicolectomy was performed subsequently in 1 case. After a mean follow-up of 52.6 months (range, 8-143 months), none had died of disease or had recurrent or metastatic disease. Our results confirm that appendiceal neuroendocrine tumors seem to have a different phenotype from those occurring in other gastrointestinal sites. Tumors less than 2 cm, even with mesoappendiceal infiltration, have an excellent prognosis, and simple appendectomy seems to be the appropriate therapeutic approach.

A 5-decade analysis of 13,715 carcinoid tumors

BACKGROUND

Carcinoid tumors represent an unusual and complex disease spectrum with protean clinical manifestations. This compilation of several large United States-based databases comprising patients from 1950 to 1999 examines 13,715 carcinoid tumors and provides epidemiologic information regarding the natural history and evolution of the detection and diagnosis of this entity.

METHODS

The authors evaluated 10,878 carcinoid tumors that were identified by the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute (NCI) from 1973 to 1999 in addition to 2837 carcinoid tumors that were registered previously by two earlier NCI programs. To the authors' knowledge, this represents the largest current epidemiology series addressing carcinoid tumors to date.

RESULTS

Specific trends in incidence for carcinoid tumors of certain sites were identified. Among the most recently collected subset of data, sites that demonstrated the greatest incidence of carcinoids were the gastrointestinal tract (67.5%) and the bronchopulmonary system (25.3%). Within the gastrointestinal tract, most carcinoid tumors occurred in the small intestine (41.8%), rectum (27.4%), and stomach (8.7%). For all sites, age-adjusted incidence rates were highest in black males (4.48 per 100,000 population per year). Associated noncarcinoid tumors were frequent in conjunction with small intestinal (29.0%), gastric (20.5%), colonic (20.0%), and appendiceal (18.2%) carcinoids. The highest percentages of nonlocalized lesions were noted for cecal (81.5-83.2%) and pancreatic (71.9-81.3%) carcinoids, whereas the highest percentage of localized disease was found among rectal (81.7%), gastric (67.5%), and bronchopulmonary (65.4%) carcinoids. The best 5-year survival rates were recorded for patients with rectal (88.3%), bronchopulmonary (73.5%), and appendiceal (71.0%) carcinoids; these tumors exhibited invasive growth or metastatic spread in 3.9%, 27.5%, and 38.8% of patients, respectively.

CONCLUSIONS

Carcinoids appear to have increased in overall incidence over the past 30 years; for some sites, this trend has been evident for nearly half a century. Recent marked increases in gastric and rectal carcinoids and a concomitant decrease in appendiceal carcinoid incidence may be due in part to varying rules of registration among the compiled databases examined in this report or to improvements in diagnostic technology; increased awareness of and about carcinoid tumors also may play a significant role. In 12.9% of all patients with carcinoid, distant metastases already were evident at the time of diagnosis; the overall 5-year survival rate for all carcinoid tumors, regardless of site, was 67.2%. These findings bring into question the widely promulgated relative benignity of carcinoid disease. Certain carcinoid tumors, such as those of the rectum, appear to be over-represented among the black and Asian populations within the United States, suggesting the role of genetics in the development of this intriguing disease.

Carcinoid tumors of the appendix in children: two case reports and review of the literature

Carcinoid is the most common tumor of the appendix. Reported incidence in pediatric population is 1 per 100,000 per annum. Clinical presentation like acute appendicitis is frequent, but carcinoid tumor can be an incidental finding during surgical procedures other than appendectomy. Size and depth of invasion are important prognostic criteria and tumors larger than 2 cm metastasize more frequently than smaller ones. Simple appendectomy is considered appropriate treatment, while right colectomy is indicated in tumor bigger than 2 cm. The authors report 2 cases of carcinoid tumors of the appendix in children, smaller than 2 cm treated with appendectomy alone, and disease free at follow-up.

Morphological-histochemical study of intestinal carcinoids and K-ras mutation analysis in appendiceal carcinoids

Intestinal carcinoids are potentially malignant neoplasms. Their histogenesis and pathogenesis are currently uncertain. The morphological and histochemical characteristics of twenty intestinal carcinoids are studied. The primary sites of three mucin-producing tumors were examined by electron microscope. Furthermore 11 appendiceal carcinoids were analysed by the polymerase chain reaction (PCR) for the detection of ras and p53 point mutations. Microscopically all carcinoids were of mixed type. Focal mucin production was evident in three carcinoids that metastasised to regional lymph nodes. HID-Alcian blue staining proved that mucin in both primary and secondary foci did not belong to the sulphated group. The secretory granules and mucin droplets found in a single neoplastic cell suggest that carcinoids of the small intestine and some of the appendix arise from the endoderm. Neither ras nor p53 mutations were detected. It seems that ras oncogenes are probably not involved in the pathogenesis of appendiceal carcinoids.

Review article: current status of gastrointestinal carcinoids

Carcinoid tumours are enigmatic, slow growing malignancies which occur most frequently (74%) in the gastrointestinal tract. In recent years, it has become apparent that the term 'carcinoid' represents a wide spectrum of different neoplasms originating from a variety of different neuroendocrine cell types. Carcinoid lesions are usually identified histologically by their affinity for silver salts, by general neuroendocrine markers, or more specifically by immunocytochemistry using antibodies against their specific cellular products. Within the gut, the most frequent sites are the small bowel (29%), the appendix (19%) and rectum (13%). Clinical manifestations are often vague or absent. Nevertheless, in approximately 10% of patients the tumours secrete bioactive mediators which may engender various elements of characteristic carcinoid syndrome. In many instances the neoplasms are detected incidentally at the time of surgery for other gastrointestinal disorders. The tendency for metastatic spread correlates with tumour size, and is substantially higher in lesions larger than 2.0 cm. An association with noncarcinoid neoplasms is ascribed in 8-17% of lesions. Treatment consists of radical surgical excision of the tumour, although gastric (type I and II) and rectal carcinoids may be managed with local excision. Overall 5-year survival is excellent for carcinoids of the appendix (86%) and rectum (72%), whereas small intestinal (55%), gastric (49%) and colonic carcinoids (42%) exhibit a far worse prognosis.

A retrospective analysis of 1570 appendiceal carcinoids

OBJECTIVE

Information about the management and outcome of appendiceal carcinoids is sparse, because few series comprise more than 100 cases. In this study we have analyzed the epidemiology of 1570 appendiceal carcinoids, to compare outcome with other gastrointestinal carcinoid tumors.

METHODS

We evaluated 1570 appendiceal carcinoids in a series of 8305 carcinoid tumors from the SEER, the End Results Group, and the Third National Cancer Survey programs of the National Cancer Institute over the time period 1950-1991.

RESULTS

Appendiceal carcinoids comprised 18.9% of all carcinoid tumors and exhibited a marked female predominance (M/F ratio: 0.47). Age-adjusted incidence rates were 1.7-fold higher in women compared to men. Appendiceal carcinoids present earlier (average age: 42.2 yr) than other gastrointestinal carcinoids (62.9 yr) or noncarcinoid appendiceal tumors (61.9 yr). At the time of diagnosis 35.4% were nonlocalized. The overall 5-yr survival for localized lesions was 94%, for regional invasion 84.6%, and for distant metastases 33.7%. The 5-yr survival of appendiceal carcinoids (85.9%) was the highest among all types of carcinoid tumors. In 14.6% noncarcinoid tumors at other sites were also evident.

CONCLUSION

The high relative incidence of carcinoid tumors in the appendix is still poorly understood. The good overall 5-yr survival rates of appendiceal carcinoids as opposed to other carcinoids represents either a different biological behavior, earlier diagnosis, or expeditious management (appendectomy). However, the increased likelihood of coexisting neoplasms and the not uncommon presentation of metastatic disease should warrant careful evaluation and postoperative follow-up of such lesions.

An analysis of 8305 cases of carcinoid tumors

BACKGROUND

Carcinoid tumors are unusual and most reports are anecdotal or limited in number. A series of 2837 cases was published in 1975. No recent large series is available.

METHODS

The authors evaluated 5468 cases identified by the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute (NCI) from 1973 to 1991 together with 2837 carcinoid cases previously registered by 2 earlier NCI programs. To the authors' knowledge, the 8305 carcinoid tumors analyzed represent the largest current epidemiology series to date.

RESULTS

The most frequent sites for carcinoids were the gastrointestinal (GI) tract (73.7%) and the bronchopulmonary system (25.1%). Within the GI tract, most occurred in the small bowel (28.7%), appendix (18.9%), and rectum (12.6%). For all sites, age-adjusted incidence rates were highest in African American males (2.12 per 100,000 population per year). Associated noncarcinoid tumors were frequent in conjunction with small intestinal (16.6%), appendiceal (14.6%), and colonic carcinoids (13.1%). The highest percentage of nonlocalized lesions were noted for pancreatic (76.1%), colonic (71.2%), and small intestinal carcinoids (70.7%) and this corresponded to their poor 5-year survival rates (34.1%, 41.6%, and 55.4%, respectively). The best 5-year survival rates were recorded for appendiceal (85.9%), bronchopulmonary (76.6%), and rectal carcinoids (72.2%). These exhibited invasive growth or metastatic spread in only 35.4%, 27.2%, and 14.2% of cases, respectively.

CONCLUSIONS

Carcinoids appear to have increased in incidence in the past 20 years. In part, this may be due to different surgical rules of the various registries, improved diagnostic technology, and increased awareness. A cumulative analysis of all types of carcinoid tumors in the SEER group indicates that in 45.3% metastases are already evident at the time of diagnosis. The overall 5-year survival rate of all carcinoid tumors regardless of site was 50.4% +/- 6.4%.

An analysis of 8305 cases of carcinoid tumors

BACKGROUND

Carcinoid tumors are unusual and most reports are anecdotal or limited in number. A series of 2837 cases was published in 1975. No recent large series is available.

METHODS

The authors evaluated 5468 cases identified by the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute (NCI) from 1973 to 1991 together with 2837 carcinoid cases previously registered by 2 earlier NCI programs. To the authors' knowledge, the 8305 carcinoid tumors analyzed represent the largest current epidemiology series to date.

RESULTS

The most frequent sites for carcinoids were the gastrointestinal (GI) tract (73.7%) and the bronchopulmonary system (25.1%). Within the GI tract, most occurred in the small bowel (28.7%), appendix (18.9%), and rectum (12.6%). For all sites, age-adjusted incidence rates were highest in African American males (2.12 per 100,000 population per year). Associated noncarcinoid tumors were frequent in conjunction with small intestinal (16.6%), appendiceal (14.6%), and colonic carcinoids (13.1%). The highest percentage of nonlocalized lesions were noted for pancreatic (76.1%), colonic (71.2%), and small intestinal carcinoids (70.7%) and this corresponded to their poor 5-year survival rates (34.1%, 41.6%, and 55.4%, respectively). The best 5-year survival rates were recorded for appendiceal (85.9%), bronchopulmonary (76.6%), and rectal carcinoids (72.2%). These exhibited invasive growth or metastatic spread in only 35.4%, 27.2%, and 14.2% of cases, respectively.

CONCLUSIONS

Carcinoids appear to have increased in incidence in the past 20 years. In part, this may be due to different surgical rules of the various registries, improved diagnostic technology, and increased awareness. A cumulative analysis of all types of carcinoid tumors in the SEER group indicates that in 45.3% metastases are already evident at the time of diagnosis. The overall 5-year survival rate of all carcinoid tumors regardless of site was 50.4% +/- 6.4%.

Dual carcinoid/epithelial neoplasia of the appendix

We report a series of 13 lesions of the human vermiform appendix in which a carcinoid component was associated with a separate non-carcinoid epithelial component that included an adenoma-like lesion of the mucosal epithelium. We use the term dual carcinoid/epithelial neoplasia to describe this phenomenon. The carcinoid component was insular/trabecular in nine cases, tubular in one case and of goblet cell type in three. The epithelial component was a mucinous cystadenoma in four, a mucinous tumour of uncertain malignant potential in three, and a mucinous cystadenocarcinoma in six. No intermediate cell population was seen and in three cases the carcinoid and epithelial components were in different parts of the appendix, leading us to suggest that these lesions may be true 'collision' tumours in which two neoplasms have arisen in the same organ. The prognosis appears to be no worse than for either of the components alone, but conclusions regarding these lesions must be guarded on account of their rarity and the small numbers available for study.

Neoplastic lesions of the appendix

Neoplasms occur in 0.5 per cent of appendices. Ultrasonography or computed tomography is beneficial, but preoperative detection is rare. At operation, the diagnosis is considered in under half of cases. Mucocele, localized pseudomyxoma peritonei, benign tumours and most appendiceal carcinoids are cured by appendicectomy alone. Right hemicolectomy is indicated for: (1) invasive adenocarcinoma; (2) tumours close to the caecum; (3) lesions larger than 2 cm; (4) mucin production; (5) invasion of the lymphatics, serosa or mesoappendix; and (6) cellular pleomorphism with a high mitotic rate. Tumours of 1-2 cm, small mucinous carcinoids, adenocarcinoma confined to the mucosa, and tumours in children may be treated by appendicectomy alone at the surgeon's discretion. The 5-year survival rate associated with classical carcinoid is more than 90 per cent. The prognosis of mucinous carcinoid is intermediate between that of classical carcinoid and well differentiated adenocarcinoma. The prognosis of adenocarcinoma is determined by Dukes' stage and is similar, stage for stage, to that of colorectal carcinoma.

Carcinoid tumors of the appendix

OBJECTIVE

A retrospective study of 41 patients with histologically confirmed diagnosis of appendix carcinoid tumors was undertaken by reviewing the surgical records at Massachusetts General Hospital.

METHODS

There were 8 male and 33 female patients (mean age 32 years). Twenty-two patients (54%) presented with signs and symptoms suggestive of acute appendicitis. In 19 patients (46%) the lesions were discovered incidentally. The tumors were located in 32 patients at the tip, in 6 patients in the middle third, and in 3 patients at the base of the appendix. The tumor was less than 1 cm in diameter in 32 patients, between 1 and 2 cm in 7 patients, and was bigger than 2 cm in 2 patients. In 29 patients, the depth of tumor penetration was confined to the submucosa or to the muscle layers of the appendix, and in 8 patients the serosa was involved. In 4 patients, evidence of tumor extension into the meso-appendicular fat was present, including one patient with a tumor bigger than 2 cm and local lymph-node metastases. Forty patients underwent appendectomy alone. One patient with a tumor size bigger than 2 cm in diameter with positive lymph nodes in the mesoappendix underwent secondary right hemicolectomy. Complete follow-up was achieved in 35 patients, and all patients remained free of tumor recurrence.

CONCLUSIONS

The authors conclude that appendiceal carcinoids are rare and most often are asymptomatic. Tumors of less than 1 cm are adequately managed by appendectomy alone. The appropriate treatment for tumors of 1 to 2 cm continues to be controversial. Right hemicolectomy is recommended for all tumors larger than 2 cm, whereas preference for an aggressive approach should be given in young patients.

The histogenesis of appendiceal carcinoid tumours

Twenty-two appendiceal carcinoid tumours, comprising 10 classical carcinoids, six tubular carcinoids and six goblet cell carcinoids were examined by histochemistry and immunohistochemistry. All of the tumours showed evidence of neuroendocrine differentiation. Classical carcinoids were invariably intimately associated with S-100 protein positive cells, supporting an origin from sub-epithelial neuroendocrine cells. Both tubular and goblet cell carcinoids expressed cytoplasmic mucin and immunoglobulin A, and neither were associated with S-100 protein positive cells. These observations suggest that tubular and goblet cell carcinoids are derived from epithelial crypt stem cells.