The AAPC case, with an early onset of colorectal cancer

Incidental Finding of Attenuated Familial Adenomatous Polyposis

Attenuated familial adenomatous polyposis (AFAP) or attenuated adenomatous polyposis coli (AAPC) is defined as the milder polyposis phenotype of classic familial adenomatous polyposis (FAP). FAP syndromes are caused by germline mutations in the adenomatous polyposis coli (APC) gene. AFAP is an inherited autosomal dominant with predominant mutations at the far proximal (5′) end of the APC gene. Unlike FAP, AFAP is characterized by the occurrence of fewer than 100 adenomas that are found mostly in the proximal part of the colon with a delayed progression to colorectal cancer (CRC). The lower risk of development of colorectal cancer and extra-intestinal neoplasms is likely attributable to under-diagnosis. However, 2-5% of all CRCs happen because of inherited syndromes which include both hereditary polyposis syndromes and hereditary nonpolyposis colorectal cancer syndrome (HNPCC) or otherwise known as Lynch syndrome (LS). Here, we present a case of a 64-year-old Polish-speaking female in whom an incidental finding of polyposis turned out to be a malignancy. Our patient had a positive family history of colon cancer. The delay in performing an annual colonoscopy with endoscopic polypectomy per AFAP surveillance guidelines was supposedly delayed due to lack of insurance and language barrier. There were no metastases and she was negative for the APC gene mutation. Pathology was significant for moderately differentiated adenocarcinoma with intact mismatch repair protein (MMRP) (expression of MLH1, PMS2, MSH2, and MSH6) genes immune-histochemical staining. The patient underwent a subtotal colectomy with ileostomy without any complications. This study aimed to emphasize that communication with the patient in their primary language is essential to gather all the data which can lead to an accurate diagnosis and to provide adequate care. Physicians are required to have a professional interpreter to acquire the appropriate medical history and be more vigilant in following up with the patient in order to provide comprehensive care.

Colorectal cancer in the course of familial adenomatous polyposis syndrome ("de novo" pathogenic mutation of APC gene): case report, review of the literature and genetic commentary

Colorectal cancer (CRC) is one of the most common malignant tumours in Poland. Annually approximately 11 000 new cases of CRC are diagnosed, while the number of deaths caused by CRC approaches 8 000. Five-year survival does not exceed 20%. Familial adenomatous polyposis (FAP) is responsible for about 1% of new cases of CRC. The risk of CRC in FAP syndrome is 100%, and the average age of CRC development is 39 years. Early colectomy is the most effective method of CRC prevention. We report an atypical case of CRC in a patient with FAP caused by 2797-2800delAACA mutation of the APC gene.

APC gene mutations causing familial adenomatous polyposis in Polish patients

Familial adenomatous polyposis (FAP) is a well-known hereditary condition characterised by alimentary system tumours. Tens to thousands of polyps occur in the colon and rectum of the patients. There is a high heterogeneity with regard to the number and time of the occurrence of polyps. The occurrence of FAP is associated with mutations in the APC tumour suppressor gene, which was described in 1991. Since then, many studies have been done to analyse the distribution of mutations in individual populations and to determine the function of the gene and a diagnostic approach to FAP. Here the APC gene was studied with respect to the occurrence of small mutations and large rearrangements in 300 unrelated Polish FAP families. Ninety-seven mutations were identified in 164 families. Out of these mutations, 80 were small mutations, including 58 small mutations that were first identified in the Polish population (42 novel and 16 described previously). An increased frequency of mutation c.3927_3931delAAAGA was observed in 10% of the Polish group. Seventeen large rearrangements were found in 29 families. Out of those rearrangements, 8 repeat rearrangements occurred in 20 families. A problem in fast molecular diagnostics of FAP is a high heterogeneity of mutations in the APC gene. It seems that a multiplex ligation-dependent probe amplification test and searching for small mutations by the use of screening methods at the 5' end of exon 15 and exons 14, 9, 11, 13, 5, and 3, help to improve the molecular diagnostics of FAP in Polish patients.

Occurrence of adenomas in the pouch and small intestine of FAP patients after proctocolectomy with ileoanal pouch construction

PURPOSE

Proctocolectomy with ileoanal pouch construction is the standard therapy for patients with familial adenomatous polyposis coli (FAP) to prevent the genesis of colorectal carcinomas. In our patient population, we observed the postoperative development of adenomas not only in the pouch but also in the remaining small intestine. The exact incidence of these ileal polyps is still unknown, since the diagnostic possibilities of examining the small intestine are limited.

METHODS

We performed wireless capsule endoscopy (CE) in patients who developed postoperative pouch adenomas (PA) to record the simultaneous occurrence of small bowel adenomas and PA. We operated on 46 patients with FAP (m:f 17:10, age 33 +/- 9 years). Thirty-five patients underwent proctocolectomy with ileoanal pouch creation. Pouch endoscopy was performed in regular intervals at 3 months and then annually after proctocolectomy. Capsule endoscopy was additionally carried out in all patients with PA.

RESULTS

Ileal PA occurred in 22.8% (n = 8) of the patients with proctocolectomy (n = 35) after a mean of 5 years after surgery. Eight PA patients (all with PA) also had adenomas in the small intestine diagnosed by CE.

CONCLUSIONS

Since jejunal and ileal adenomas occur in all patients with PA, we recommend regular follow-up examinations, which include pouch endoscopy at 3 months and annually after surgery in the presence of PA after proctocolectomy and pouch creation. On the basis of our observations, we recommend adding CE or double-balloon enteroscopy to the follow-up examination.

Novel APC mutations in Czech and Slovak FAP families: clinical and genetic aspects

Background

Germline mutations in the adenomatous polyposis gene (APC) result in familial adenomatous polyposis (FAP). FAP is an autosomal dominantly inherited disorder predisposing to colorectal cancer. Typical FAP is characterized by hundreds to thousands of colorectal adenomatous polyps and by several extracolonic manifestations. An attenuated form of polyposis (AFAP) is characterized by less than 100 adenomas and later onset of the disease.

Methods

Here, we analyzed the APC gene for germline mutations in 59 Czech and 15 Slovak FAP patients. In addition, 50 apparently APC mutation negative Czech probands and 3 probands of Slovak origin were screened for large deletions encompassing the APC gene. Mutation screening was performed using denaturing gradient gel electrophoresis and/or protein truncation test. DNA fragments showing an aberrant electrophoretic banding pattern were sequenced. Screening for large deletions was performed by multiplex ligation dependent probe amplification. The extent of deletions was analyzed using following microsatellite markers: D5S299, D5S82, D5S134 and D5S346.

Results

In the set of Czech and Slovak patients, we identified 46 germline mutations among 74 unrelated probands. Total mutation capture is 62,2% including large deletions. Thirty seven mutations were detected in 49 patients presenting a classical FAP phenotype (75,5%) and 9 mutations in 25 patients with attenuated FAP (36%). We report 20 novel germline APC mutations and 3 large deletions (6%) encompassing the whole-gene deletions and/or exon 14 deletion. In the patients with novel mutations, correlations of the mutation localization are discussed in context of the classical and/or attenuated phenotype of the disease.

Conclusion

The results of the molecular genetic testing are used both in the establishment of the predictive diagnosis and in the clinical management of patients. In some cases this study has also shown the difficulty to classify clinically between the classical and the attenuated form of FAP according to the established criteria. Interfamilial and/or intrafamilial phenotype variability was also confirmed in some cases which did not fit well with predicted genotype-phenotype correlation. All these findings have to be taken into consideration both in the genetic counselling and in the patient care.