MCQ – 88475

A 70-year-old woman presents with a 3-month history of diarrhea and abdominal pain. She has lost 9 kg (20 lb) in the past 6 months. The patient had two benign colonic polyps removed 3 years ago. Laboratory studies reveal mild iron-deficiency anemia, and stool specimens are positivefor occult blood. Sigmoidoscopy demonstrates an ulcerated mass, and a biopsy shows malignant glands. A segment of the colon is resected, and the surgical specimen is shown in the image. Based on current models of colonic carcinogenesis, which of the following genes was most likely mutated in the transition from benign adenoma to carcinoma in thisPatient?

Correct Answer � C Explanation

Answer : C P53

In most cases of colorectal carcinoma, it has been estimated that a minimum of eight to ten mutational events must accumulate before the development of invasive cancer. This process is initiated in morphologically normal mucosa, proceeds through an adenomatous precursor, and terminates as invasive adenocarcinoma. 

The APC gene is considered to play an important role in the early development of most colorectal neoplasms, whereas mutations in the p53 tumor suppressor gene are thought to participate in the late transition from adenoma to carcinoma. BRCA1 has been implicated in the pathogenesis of breast and ovarian cancers.