Familial polyposis coli and its extracolonic manifestations

Medulloblastoma genomics in the modern molecular era

Medulloblastoma (MB) represents a spectrum of biologically and clinically distinct entities. Initially described histopathologically as a small, round blue cell tumor arising in the cerebellum, MB has emerged as a paradigm for molecular classification in cancer. Recent advances in genomic, transcriptomic and epigenomic profiling of MB have further refined molecular classification and complemented conventional histopathological diagnosis. Herein, we review the main clinical and molecular features of the four consensus subgroups of MB (WNT, SHH, Group 3 and Group 4). We also highlight hereditary predisposition syndromes associated with increased risk of MB. Finally, we explore advances in the classification of the consensus molecular groups while also presenting cutting-edge frontiers in identifying intratumoral heterogeneity and cellular origins of MB.

Possible Considerations for the Management of Turcot’s Syndrome?

Background:

Turcot’s syndrome (TS) is a rare disease with known incidence of about 1-2 cases per year. It is, however, linked to high mortality due to the brain cancer. And because of this, we propose recommendations, aimed at preventing the mortality of the patients and to minimize the risk of undiagnosed Turcot’s syndrome.

Methods:

The authors collected the worldwide published data on TS, from the year of its definition till 2018, all of which was published on the search engines, such as Medline, Medknow, Cohraine and Wiley.

Results:

We included 97 patients, 57 from which are females and 40 males with median age of 22 years. The most common type of cancer is medulloblastoma, followed by glioblastoma and astrocytoma. We further divided the patients into two categories based on the first symptom of the disease and we made an algorithm of approaching these patients.

Conclusion:

TS is a disease that affects mostly members of families with multiple genetic mutations and types of cancers. And because of the unknown mechanisms of inheritance, it is useful to establish guidelines for the approach of those patients, in order to minimize the high mortality rate.

Medulloblastoma

Medulloblastoma (MB) comprises a biologically heterogeneous group of embryonal tumours of the cerebellum. Four subgroups of MB have been described (WNT, sonic hedgehog (SHH), Group 3 and Group 4), each of which is associated with different genetic alterations, age at onset and prognosis. These subgroups have broadly been incorporated into the WHO classification of central nervous system tumours but still need to be accounted for to appropriately tailor disease risk to therapy intensity and to target therapy to disease biology. In this Primer, the epidemiology (including MB predisposition), molecular pathogenesis and integrative diagnosis taking histomorphology, molecular genetics and imaging into account are reviewed. In addition, management strategies, which encompass surgical resection of the tumour, cranio-spinal irradiation and chemotherapy, are discussed, together with the possibility of focusing more on disease biology and robust molecularly driven patient stratification in future clinical trials.

Family history of cancer among children with brain tumors: a critical review

The occurrence of brain tumors in children has been anecdotally associated with an increased cancer incidence among relatives. This study rigorously reviewed the epidemiologic literature regarding family history of cancer in children with brain tumors. Six case-control and 10 cohort studies remained after applying stringent inclusion criteria. Most studies found no significant increase in cancer risk among relatives of childhood brain tumor patients. Those associations that were detected were often of borderline significance or demonstrated wide confidence intervals. There is limited evidence that a family history of cancer is more common among families of childhood brain tumor patients.

A homozygous mutation in MSH6 causes Turcot syndrome

Heterozygous mutations in one of the DNA mismatch repair genes cause hereditary nonpolyposis colorectal cancer (MIM114500). Turcot syndrome (MIM276300) has been described as the association of central nervous system malignant tumors and familial colorectal cancer and has been reported to be both a dominant and recessive disorder. Homozygous and compound heterozygous mutations in APC, MLH1, MSH2, and PMS2 genes have been reported in five families. Here we describe a nonconsanguineous Pakistani family, including a son with lymphoma and colorectal cancer diagnosed at ages 5 and 8, respectively, and an 8-year-old daughter with glioblastoma multiforme. Both children had features of neurofibromatosis type 1 including atypical café au lait spots and axillary freckling without a family history consistent with neurofibromatosis type 1, familial adenomatous polyposis, or hereditary nonpolyposis colorectal cancer. Mutational analysis was done for MLH1, MSH2, and MSH6 using denaturing high-performance liquid chromatography and sequencing of a blood sample from the daughter. A novel homozygous single base insertion mutation was identified (3634insT) resulting in a premature stop at codon 1,223 in exon 7 of the MSH6 gene. Both parents were found to be heterozygous for the 3634insT mutation. Microsatellite instability testing showed instability in the glioblastoma sample. We report here the first identification of a homozygous mutation in MSH6 in a family with childhood-onset brain tumor, lymphoma, colorectal cancer, and neurofibromatosis type 1 phenotype. Our findings support a role for MSH6 in Turcot syndrome and are consistent with an autosomal recessive mode of inheritance.

Turcot syndrome in an elderly adult

A 67-year-old woman presented with hematochezia and an episode of transient expressive dysphasia. She was found to have multiple colonic polyps with adenocarcinomatous changes. Computed tomography brain scan and computed tomography-guided biopsy revealed a left frontoparietal glioblastoma multiforme. This case illustrates the rare presentation of Turcot syndrome-a hereditary colorectal polyposis syndrome-in an older adult.

Familial nonmedullary thyroid neoplasia

Thyroid carcinoma accounts for less than 1% of all human malignancies and carries one of the highest overall familial relative risks as compared with cancers from other sites. This is particularly true for medullary carcinoma, as well as for carcinomas of follicular cell origin in general, where inheritance has been implicated in 2.5 to 6.3% of the cases. Familial nonmedullary thyroid tumors show a variety of genetic mechanisms implicated in thyroid tumorigenesis and occur in several tumor-prone traits (e.g., familial adenomatous polyposis [FAP] and Cowden's disease [CD]) or as the only or dominant inherited manifestation. The latter group includes the most common familial papillary carcinoma, in which environmental factors such as radiation exposure may also play an important etiological role. Familial follicular cell tumors show a variety of morphological features ranging from benign thyroid nodulation to carcinoma, usually develop in young individuals, and tend to be multicentric--an indication for total thyroidectomy to avoid tumor recurrence and potential risk of malignant transformation. The pathologist may play an important role in the histological interpretation of familial nonmedullary thyroid tumors, which may lead to further clinicogenetical investigations of the affected patient and family screening. Familial follicular cell thyroid neoplasms show a complex molecular biological pathway of tumorigenesis when compared between themselves and with their sporadic counterparts.

A father and son with Turcot's syndrome: evidence for autosomal dominant inheritance: report of two cases

Typical Turcot's syndrome is characterized by the association of a brain glioma together with multiple colonic polyposis, in which the number of polypoid lesions is small and the association of colonic cancer occurs at a younger age than in familial adenomatous polyposis. We describe a family in which both the father and his son presented with typical Turcot's syndrome without parental consanguinity. This is the first report of a family that is considered to follow an autosomal dominant inheritance. After reviewing 25 documented cases in which the average age of death was 20.3 years old, it was learned that the major cause of death was brain tumor (76 percent) and the minor cause was colon cancer (16 percent). Patients were very young and, therefore, unlikely to have produced a child before their death. These facts seem to support the theory that Turcot's syndrome is an autosomal dominant disorder.

Genetic alterations in a patient with Turcot's syndrome

Turcot's syndrome (TS) is a rare disorder associated with the development of both brain and colon neoplasms. Because of the very low incidence of the disease, its molecular basis remains unclear. Presented is a TS case of a 30-year-old Japanese male with a histopathologically confirmed diagnosis of both brain tumor (glioblastoma multiforme) and colon tumor (well-differentiated adenocarcinoma). Germline mutations of the p53 gene, somatic mutations of the Ki-ras, p53 and APC genes, and microsatellite instability (MSI) was examined using polymerase chain reaction (PCR)-single strand conformation polymorphism analysis, followed by PCR-direct sequencing, and sequencing after subcloning. No germline mutations of the p53 gene were found. Somatic mutations of Ki-ras and APC genes were found in the colon adenocarcinoma but not in the brain tumor. No somatic mutation of the p53 gene was present in either colon or brain tumors. Microsatellite instability of both colon and brain tumors was positive in two of four loci. These results indicate that the colon tumor of the TS patient carries the Ki-ras and APC gene mutations. The finding of MSI in both the brain and the colon tumors may support the hypothesis that alterations of DNA repair genes are involved in the tumor development of the TS patient.

Multiple ependymomas in a patient with Turcot's syndrome

A 21-year-old woman was diagnosed with Turcot's syndrome (TS) at age 16 years. She had two ependymomas, one was located in the left middle cerebellar peduncle and the other in the low sacral spinal canal. Her mother and brother both had colectomies for colonic polyposis. Her maternal uncle and grandfather also had this disease and both died from cancer of the colon in their fourth decade of life. The patient was found to have hyperpigmented spots in the retina, skull osteomas and normal neurological examinations. The bone scan and CSF were normal and she had a germline mutation in the segment 3 of the adenomatous polyposis coli (APC) gene. Following partial resection of the two ependymomas, she was treated with radiation and chemotherapy. One year after surgery, paraspinal desmoid tumors were found and removed. She is presently 42 months postsurgical resection of the neural tumors and has remained central nervous system tumor-free. The occurrence of multiple ependymoma in TS has not been reported, and the control of this patient's ependymomas is consistent with other reports of long-term survival with TS and glial tumors.

The molecular basis of Turcot's syndrome

BACKGROUND

Turcot's syndrome is characterized clinically by the concurrence of a primary brain tumor and multiple colorectal adenomas. We attempted to define the syndrome at the molecular level.

METHODS

Fourteen families with Turcot's syndrome identified in two registries and the family originally described by Turcot and colleagues were studied. Germ-line mutations in the adenomatous polyposis coli (APC) gene characteristic of familial adenomatous polyposis were evaluated, as well as DNA replication errors and germline mutations in nucleotide mismatch-repair genes characteristic of hereditary nonpolyposis colorectal cancer. In addition, a formal risk analysis for brain tumors in familial adenomatous polyposis was performed with a registry data base.

RESULTS

Genetic abnormalities were identified in 13 of the 14 registry families. Germ-line APC mutations were detected in 10. The predominant brain tumor in these 10 families was medulloblastoma (11 of 14 patients, or 79 percent), and the relative risk of cerebellar medulloblastoma in patients with familial adenomatous polyposis was 92 times that in the general population (95 percent confidence interval, 29 to 269; P < 0.001). In contrast, the type of brain tumor in the other four families was glioblastoma multiforme. The glioblastomas and colorectal tumors in three of these families and in the original family studied by Turcot had replication errors characteristic of hereditary nonpolyposis colorectal cancer. In addition, germ-line mutations in the mismatch-repair genes hMLH1 or hPMS2 were found in two families.

CONCLUSIONS

The association between brain tumors and multiple colorectal adenomas can result from two distinct types of germ-line defects: mutation of the APC gene or mutation of a mismatch-repair gene. Molecular diagnosis may contribute to the appropriate care of affected patients.

Turcot's syndrome and familial adenomatous polyposis associated with brain tumor: review of related literature

We investigated clinical manifestations in 124 patients with a possible Turcot's syndrome whose data were taken from documented cases. The cases were subclassified mainly on the bases of the type of familial occurrence and listed in five Tables. We searched for differences in colonic manifestation, histologic type of glioma, mode of inheritance, frequency of parental consanguinity, skin lesions and other accompanying lesions among these five groups. The differences of these clinical findings suggested that glioma-polyposis syndrome should be classified as follows; (1) cases of Turcot's syndrome who had characteristic colonic and brain manifestations, (2) cases of FAP associated with glioma, (3) suspicious cases of glioma-polyposis, and (4) cases other than glioma-polyposis syndrome.

Familial adenomatous polyposis coli and clear cell sarcoma of the kidney

Familial adenomatous polyposis coli is an inherited multiple neoplasia syndrome that is associated with an increased risk for development of another primary tumor. We report a case of a 14-year-old boy who had a proctocolectomy for familial adenomatous polyposis coli. He had survived radical nephrectomy, chemotherapy, and radiotherapy for a congenital clear cell sarcoma of the right kidney. Perhaps the presence of the familial adenomatous polyposis gene induces chromosomal instability in affected persons.

Genetic evidence that Turcot syndrome is not allelic to familial adenomatous polyposis

Turcot syndrome (TS) is a rare genetic disease in which brain tumors occur in association with colonic polyposis. Since Turcot's original description in 1959, there have been disagreements about the mode of inheritance as well as the clinical expression of this condition. Some investigators maintain that TS is a phenotypic variant of the autosomal dominant familial adenomatous polyposis (FAP), while others observe that there are clinical differences between TS and FAP, and that the pattern of inheritance of TS is autosomal recessive. The distribution of persons with colonic lesions in a family with a patient of colonic polyposis and a brain tumor, described in this report, favored the recessive hypothesis. In this family, the involvement of the FAP gene on chromosome 5q21-q22 could be excluded by a linkage study using a panel of FAP-linked DNA markers. This finding, which indicates the occurrence of another polyposis gene elsewhere in the genome, will have consequences for the presymptomatic diagnosis of FAP by linked DNA markers. We conclude that TS is a distinct clinical-genetical entity with the triad of atypical polyposis coli, CNS tumors, and a recessive mode of inheritance.

Familial polyposis coli: the spectrum of ocular and other extracolonic manifestations

Familial polyposis coli (FPC) is hereditary condition that conveys a virtual 100% risk for the development of colon cancer in the untreated patient. A total of 56 patients with FPC underwent complete ophthalmic examination. Highly pleomorphic pigmented retinal lesions were identified bilaterally in 52% (n = 29) and unilaterally in 14% (n = 8) of our subjects. In all, 33 patients had one or more extracolonic expressions associated with FPC, including desmoids, osteomas, epidermoid cysts, lipomas, fibromas, and upper gastrointestinal tract polyps. In 15 patients, pigmented fundus lesions were the only extracolonic manifestations. No significant association between eye findings and other extracolonic manifestations could be established. The presence or absence of pigmented fundus lesions was found to cluster within families. Pigmented fundus lesions are probably a variably penetrant expression of the polyposis gene and do not appear to be specifically associated with subgroups of inherited polyposis syndromes such as Gardner's syndrome.

[Turcot syndrome: a report of 2 cases]

The authors describe two patients with the association of polyposis-coli and central nervous system tumor (Turcot's syndrome). Clinical, genetic and therapeutic aspects are discussed.

Brain tumors in familial adenomatous polyposis

Familial adenomatous polyposis was always believed to be a colonic disease of genetic determination with a high risk of development of cancer of the large bowel. Over the years the list of extracolonic manifestations of this disease, both benign and malignant, has amplified. Brain tumors and, in particular, medulloblastoma have not become recognized as major malignant extracolonic manifestations of familial adenomatous polyposis. They are of particular significance because, unlike most of the other manifestations, they occur prior to or early in the development of the colonic manifestations of this disease. This report documents the investigation of 168 kindreds in The Cleveland Clinic Familial Adenomatous Polyposis Registry in a search for those at-risk individuals who developed brain tumors.

Familial adenomatous polyposis

Familial adenomatous polyposis is an autosomal dominant disease that includes early development of up to thousands of colorectal adenomas and several extracolonic manifestations. All untreated patients will develop colorectal adenocarcinoma. The treatment of choice is colectomy and ileorectal anastomosis, but restorative proctocolectomy may be considered in selected cases. Polyposis patients treated with ileorectal anastomosis should be followed for life, with regular proctosigmoidoscopy and destruction of new adenomas. Furthermore, regular gastroduodenoscopy should be carried out because of frequent occurrence of premalignant duodenal adenomas. The prognosis is good after prophylactic colectomy in patients without carcinoma. All first degree relatives of affected family members should be examined regularly with proctosigmoidoscopy from the age of ten, and prophylaxis should be organised using a national or regional polyposis register. The recent detection of a specific gene for familial adenomatous polyposis is a long step forward, and several problems may be solved by increasing international cooperation.

Mesenteric desmoid tumours in Gardner's syndrome--review of medical treatments

Gardner's syndrome comprises a triad of polyposis coli, osteomata and soft tissue tumours including desmoid tumours which can often present difficult problems in management. We report a patient with Gardner's syndrome treated with tamoxifen and medroxyprogesterone acetate. The literature on this rare syndrome and its management is reviewed.

[Severity of desmoid tumors with retroperitoneal development in Gardner's syndrome. Apropos of 2 cases]

We report two cases of retroperitoneal desmoid tumours in patients with Gardner's syndrome. These tumours are rare and of poor prognosis. In our two cases, the predominant clinical manifestations were caused by compression of the ureters, bladder and nerve roots. In the first patient, the tumours developed after colectomy, while in the second patient the discovery of the desmoid tumour preceded that of a cancer of the colon. Finally, in the first patient, an attempted treatment with a non-steroidal anti-inflammatory agent (sulindac) had to be discontinued after 4 months on account of side-effects.

The possible presence of a separate disease entity in nonfamilial polyposis of the large intestine

Familial adenomatosis coli (FAC) traditionally has been diagnosed as the presence of more than 100 colonic adenomas, even if no familial occurrence is present. In the present communication, clinical features of FAC have been compared in detail to detect differences between familial and nonfamilial cases with regard to colonic and extracolonic lesions and to discover whether they constitute the same disease entities. No significant difference was found in the incidence of extracolonic lesions. The average number of colonic polyps in the nonfamilial cases of patients over 30 years old was 1128, the number of polyps was significantly higher in the familial cases (3154). When three patients with approximately 100 polyps were excluded, the mean number of colonic polyps in nonfamilial cases became 2608. This was similar to that of familial cases. Furthermore, the occurrence of approximately 100 polyps was extremely rare in familial patients who were over 30 years old. Therefore, most of the nonfamilial cases can be considered to be familial probands of FAC, but some, such as the three cases in the present study, may be a different disease entity, such as recessive adenomatous polyposis or multiple colonic adenomas.

Turcot's syndrome. A review

Turcot's syndrome represents the association between familial multiple polyposis coli and neural tumors. The syndrome is reviewed with reference to genetics, colonic and central nervous system manifestations. This evidence suggests that Turcot's syndrome represents one manifestation of the pleiotropic autosomal dominant gene responsible for familial polyposis coli and the associated extracolonic manifestations of Gardner's syndrome. A diagnosis of Turcot's syndrome should be restricted to those patients with familial polyposis coli associated with gliomas or medulloblastomas. A further case is presented that is believed to be the first report of such a case in the United Kingdom.

Hyperpigmented lesions of the retinal pigment epithelium in familial adenomatous polyposis

Ophthalmic examinations were performed on 56 patients with validated familial adenomatous polyposis (FAP) for hyperpigmented defects of the retinal pigment epithelium. Such lesions were seen bilaterally in 29 patients (52%) and unilaterally in 8 patients (14%). Of the 56 patients, 33 had one or more of the extracolonic expressions associated with Gardner syndrome. We found retinal lesions in 8 patients without any of the expressions of Gardner syndrome. No association was found between Gardner syndrome and the retinal lesions when these patients were compared to patients without any stigmata of Gardner syndrome, nor was any significant association found when each of the expressions was compared individually with the presence of the pigmented retinal lesions. The presence or absence of eye findings were seen to cluster within families. There was no association with sex. Fundus lesions are apparently a variable expression of the FAP gene and are not specifically associated with Gardner syndrome.

Occult radiopaque jaw lesions in familial adenomatous polyposis coli and hereditary nonpolyposis colorectal cancer

The purposes of this study were to determine the association, in 10 pedigrees, between adenomatous polyposis coli, hereditary nonpolyposis colorectal cancer, and occult radiopaque jaw lesions, and to assess whether these radiodensities are predictors for adenomatous polyposis. In seven kindreds with adenomatous polyposis, all patients with polyps had jaw lesions; in one kindred, no jaw lesions were found. In one of two kindreds with hereditary nonpolyposis colorectal cancer, no affected individuals had jaw lesions. In the other, the 1 affected patient with dental radiographs had generalized jaw lesions. Twelve children less than 16 yr old at risk for adenomatous polyposis were observed. Seven children with jaw lesions developed polyps after a mean interval of 4 yr. Five children without jaw lesions were polyp-free during a 5-10-yr follow-up. Thus, occult jaw lesions are consistently found only in some families with adenomatous polyposis coli, providing support for heterogeneity in polyposis syndromes. Jaw lesions are good predictors for polyp development in kindreds with adenomatous polyposis coli and jaw lesions. Their role as markers in hereditary nonpolyposis colorectal cancer needs exploration.

Upper gastrointestinal neoplasia in familial polyposis

Upper gastrointestinal (UGI) endoscopy was performed in 41 asymptomatic American patients with familial polyposis to assess the prevalence of gastric and duodenal polyps and to characterize their pathological features. Eighteen patients (44%) had UGI endoscopic abnormalities. Six patients had both gastric and duodenal lesions. Eight patients had only gastric polyps, and four had duodenal polyps only. The presence of other extracolonic expressions of polyposis had a suggestive but statistically insignificant correlation with UGI polyps. Patients with familial polyposis and duodenal adenomatous polyps are at high risk for the development of periampullary cancer; screening and identification of these individuals is recommended.

Turcot syndrome. Autosomal dominant or recessive transmission?

The authors analyzed a family in which three descendants presented with adenocarcinoma of the colon. In two of them the presence of colonic adenomatosis was observed. Another family member, a 13-year-old girl, presented with Turcot syndrome, that is, brain tumor associated with colonic adenomatosis. The nature of the hereditary transmission of Turcot syndrome is hence analyzed, discussing whether it happens through an autosomal recessive or a dominant gene. Undoubtedly the family has colonic adenomatosis, a disease considered of autosomal dominant transmission. Based on the clinical observation, the authors suggest that Turcot syndrome may be determined by an autosomal gene with a pleiotropic effect and variable expressivity.

Clinical features in familial polyposis coli. Results of the Danish Polyposis Register

Three hundred nineteen affected members of 94 Danish families with familial polyposis coli had been registered in the Danish Polyposis Register by the end of 1982. Of the 247 histologically verified cases, 168 were propositi and 79 were call-up patients. The frequency of colorectal cancer at the time of diagnosis of polyposis was 69 percent in propositi vs. 3 percent in call-up patients. The cumulative survival rate after ten years was 97 percent in call-up patients, as compared to 42 percent in propositi. The prognosis of polyposis patients has improved significantly since the establishment of the Danish Polyposis Register in 1971.

Ileal adenomas in familial polyposis coli. Differences before and after colectomy

We treated two patients with familial polyposis coli (FPC) who were found to have multiple adenomas in the ileostomy stoma, five and seven years after colectomy, respectively. These adenomas were dense and 3 to 10 mm in diameter. The adjacent ileal mucosa showed a colonic metaplasia. Ileal adenomas detected using intraoperative intestinal endoscopy at the time of colectomy were less than 2 mm in diameter and sparse in density. These findings suggest that ileal adenomas occurring after colectomy for FPC tend to increase in size and number and to resemble colonic adenomas.

Turcot syndrome and its characteristic colonic manifestations

The reported clinical manifestations of Turcot syndrome were studied to determine whether these corresponded to those of Turcot's original cases. Among the patients with well-documented colonic lesions, the colonic lesions were classified into three groups. First, there was a main group in which colonic lesions had the following characteristics that coincided with those of Turcot's original cases: a low number of polyps (20-100), large polyps over 3 cm in diameter, and complication by colonic cancer during the second or third decades. In the second group, the patients had too few polyps to be diagnosed as polyposis. The third group included patients with numerous colonic polyps similar to those of familial polyposis coli. The recognition of these characteristics of colonic lesions may lead to early detection of glioma in the asymptomatic period.

Embryonal carcinoma of the testis associated with familial adenomatosis coli. Report of a case

A rare case of embryonal carcinoma of the testis associated with familial adenomatosis coli is reported. The patient may serve as a case to support the hypothesis that familial adenomatosis coli is a systemic or generalized disease with tumorigenicity that is not restricted to the colon and rectum, and that a total colectomy with ileostomy is not always entirely curative.

Exclusion of a tight linkage between familial polyposis coli and HLA

Linkage was investigated between a dominant gene determining familial polyposis coli (FPC) and HLA in a large pedigree. A tight linkage was excluded at a value of the recombination fraction between 0 and 5%. Linkage studies with various markers should be pursued to permit detection of high risk individuals and to better understand the phenotypic variability observed in certain polyposis families.

Medical aspects of hereditary intestinal polyposis

Extracolonic manifestations are often associated with familial polyposis coli, but the cysts and osteomas may be few and inconspicuous. Abnormal fibrous reactions may also occur and may be a cause of death. These manifestations act as "external markers" for the later appearances of adenomas. In any family, some individuals may manifest some extracolonic manifestations and other individuals may not. Other abnormalities, usually neoplastic, described in familial polyposis coli families, are probably fortuitous occurrences, but medulloblastoma has been found relatively frequently. Turcot's syndrome, described in a unique family, should be used more restrictively. Diagnosis depends on histology showing adenomas, but no particular number is required in an afflicted family member. Total reliance on sigmoidoscopy alone is potentially hazardous as the descending colon may be affected initially. Inherent problems regarding "isolated cases" are outlined.