A 61-year-old woman has noted a feeling of pelvic heavi ness for the past 6 months.
On physical examination, there is a palpable nontender lower abdominal mass. An abdominal
ultrasound scan shows a 12-cm solid mass in the uterine wall.
A total abdominal hysterectomy is performed. The mass has the microscopic appearance of a well-differentiated leiomyo sarcoma.
One year later, a chest radiograph shows a 4-cm nod ule in her right lower lung. Cytologic analysis of a fine-needle biopsy specimen of the nodule shows a poorly differentiated sarcoma.
The patient’s medical history indicates that she has smoked cigarettes most of her adult life. Which of the follow ing mechanisms best explains these findings?
Inheritance of a defective RB gene
Development of a second primary neoplasm