How many years does it take for stomach cancer to develop? i have read it takes many years. true or false?

Year: Almost all cancers take years to develop. However most of these years, no one is able to tell that a cancer is developing.

Several years: most stomach lesions do not start de novo as cancer but rather an inflammatory process ,first in the form of a superficial ulcer and then slowly over time converting to cancer. If one finds a somach ulcer especially along the greater curvature, a random biopsy may show inflammation but a complete excision may reveal malignant transformation. For the whole lesion to be malignant may take years