Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Familial stomach cancer ?
    ### Response:
    Familial stomach cancer is a cluster of stomach cancer within a family. Most cases of stomach cancer occur sporadically in people with little to no family history of the condition; however, approximately 10% of stomach cancer is considered "familial." Although the underlying cause of some familial cases is unknown, genetic changes (mutations) are identified in a subset of people affected by gastric cancer.
    