Most common cancer worldwide is: September 2010, March 2013
**Core Concept**
The question is testing knowledge on the epidemiology of cancer, specifically the most common type of cancer worldwide. The correct answer requires an understanding of global cancer statistics and trends.
**Why the Correct Answer is Right**
Breast cancer is the most common cancer worldwide, accounting for a significant proportion of new cancer cases and cancer-related deaths. This is due to a combination of factors, including a high incidence rate in women, particularly in developed countries, and the increasing population of women globally. The exact mechanisms underlying the high incidence of breast cancer are complex and multifactorial, involving genetic, hormonal, and lifestyle factors. The estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2) are key molecular markers in breast cancer, and their expression influences treatment decisions.
**Why Each Wrong Option is Incorrect**
**Option A:** Lung cancer is the leading cause of cancer deaths worldwide, but it is not the most common cancer overall.
**Option B:** Colorectal cancer is a common cancer in developed countries, but its incidence rate is lower than that of breast cancer globally.
**Option C:** Prostate cancer is a common cancer in men, particularly in Western countries, but its incidence rate is lower than that of breast cancer worldwide.
**Option D:** Stomach cancer is a common cancer in certain regions, such as East Asia, but its global incidence rate is lower than that of breast cancer.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that cancer epidemiology varies significantly across different populations and regions, and a global perspective is crucial for understanding cancer trends and developing effective prevention and treatment strategies.
**Correct Answer: C. Breast cancer.**