A Case of APC Gene Mutation-Associated Familial Adenomatous Polyposis With Multiple System Malignancies

Sep 23, 2026

Familial adenomatous polyposis (FAP) is an autosomal dominant disorder with a near-100% risk of colorectal cancer by age 40. The APC gene is the primary mutated gene, and mutations in specific APC regions may be linked to thyroid disorders. FAP-associated colorectal cancer often shows worse outcomes than sporadic colorectal cancer. This case report follows a 30-year-old woman with papillary thyroid carcinoma who developed metastatic colorectal cancer and an APC exon 16 deletion mutation; despite multimodal therapy, disease progressed and the patient died.

LanguageEnglish

CategoryHealthcare

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Pages9

Reading Time23 min

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Abstract

Introduction

Familial adenomatous polyposis (FAP) overview

APC gene and classification by polyp burden

Distinction from MUTYH-associated polyposis (MAP)

Cancer Reports CASE REPORT OPEN ACCESS A Case of APC Gene Mutation-Associated Familial Adenomatous Polyposis With Multiple System Malignancies Ren Yijing1 | Wang Wenjun2,3 | Gao Xiang1 | Xing Kongling1 | Chen Yunxia1 | Liao Wei4 | Zhou Ping5 1Second Ward, Department of Radiotherapy, the First Affiliated Hospital, the First School of Clinical Medicine, Hainan Medical University, Haikou, China | 2Key Laboratory of Emergency and Trauma of Ministry of Education, Engineering Research Center for Hainan Biological Sample Resources of Major Diseases & the Hainan Branch of National Clinical Research Center for Cancer & the First Affiliated Hospital, Hainan Medical University, Haikou, China | 3Research Transformation Department, Hainan Free Trade Port Health Medicine Research Institute, Baoting, China | 4Department of Respiratory Medicine, Hongsen Hospital, Harbin Medical University, Sanya, China | 5Second Ward, Department of Radiotherapy, Key Laboratory of Emergency and Trauma of Ministry of Education, the First Affiliated Hospital, Hainan Medical University, Haikou, China Correspondence: Liao Wei ([44495645@qq.com](44495645@qq.com)) | Zhou Ping ([zhoupingcsw@126.com](zhoupingcsw@126.com)) Received: 28 May 2025 | Revised: 18 September 2025 | Accepted: 24 September 2025 Funding: This work was supported by Hainan Province Science and Technology Special Fund (ZDYF2022SHFZ132, ZDYF2024SHFZ045), National Natural Science Foundation of China (82260474, 82303935), the Scientific Research Project of Health and Family Planning Industry in Hainan Province, China (22A200068) . Keywords: APC gene | colorectal cancer | familial adenomatous polyposis | thyroid cancer ABSTRACT Background: Familial adenomatous polyposis (FAP) is an autosomal dominant inherited disorder, with a nearly 100% risk of developing colorectal cancer by the age of 40. The primary gene mutated in FAP is APC, and mutations in certain regions of the APC gene may be associated with thyroid disorders, including malignant neoplasms, benign nodules, and endocrine diseases of the thyroid. FAP-associated colorectal cancer (FAP-CRC) demonstrates poorer treatment outcomes compared to sporadic colorectal cancer, which may be attributed to several factors such as distinct molecular pathogenesis, chromosomal instability (CIN), and tumor microenvironment (TME) . Case: We describe the case of a 30-year-old female patient with a history of papillary thyroid carcinoma who presented with abdominal pain. Gastrointestinal endoscopy revealed multiple polyps in the stomach and colon. Additionally, the patient was found to have metastatic colorectal cancer with hepatic and pulmonary involvement. Further genetic testing revealed a deletion mutation in the APC gene at exon 16, c.1974 _ 1975del (p.Asn659Glnfs*14) . Despite the implementation of multiple therapeutic regimens, the patient's condition showed a poor response, ultimately leading to her demise. We conducted an in-depth analysis of the potential factors contributing to this outcome. Conclusion: APC gene mutations lead to FAP and subsequent colorectal cancer, and may also predispose individuals to thyroid disorders, including malignancies, benign nodules, and endocrine dysfunction. Therefore, we recommend that young patients diagnosed with thyroid cancer undergo a thorough evaluation of family history for hereditary conditions. Additionally, consideration should be given to gastrointestinal endoscopic and ophthalmologic screening, as well as molecular genetic testing. When multiple gastric and colorectal polyps are detected, genetic alterations in APC or MUTYH should be suspected. In particular, female patients diagnosed with FAP before the age of 31 should undergo annual thyroid ultrasound surveillance. | Ren Yijing and Wang Wenjun served as co-first authors (the same contribution). Liao Wei and Zhou Ping served as corresponding authors (the same contribution) . | | --- | | This is an open access article un

FAQs

What gene mutation is associated with familial adenomatous polyposis in this report?

The report identifies a deletion mutation in the APC gene at exon 16: c.1974_1975del (p.Asn659Glnfs*14).

How does FAP increase the risk of colorectal cancer?

FAP causes multiple colorectal adenomatous polyps, and without timely diagnosis and intervention the risk of colorectal cancer approaches 100% by age 40.

What screening and evaluation does the conclusion recommend for young thyroid cancer patients?

Young patients diagnosed with thyroid cancer should receive thorough evaluation of family history for hereditary conditions, and consideration for gastrointestinal endoscopic and ophthalmologic screening plus molecular genetic testing. When multiple gastric and colorectal polyps are found, APC or MUTYH alterations should be suspected, with annual thyroid ultrasound surveillance for women with FAP diagnosed before age 31.

Sep 23, 2026

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