Below is an instruction from Human. Write a response.
    ### Instruction:
    How to diagnose Primary gastrointestinal melanoma ?
    ### Response:
    How might primary melanoma of the small intestine be diagnosed? A variety of tests may be involved in the initial diagnosis of the tumor, including contrast radiography, endoscopy, and CT scan. The tumor is confirmed by surgical resection. Careful study of tissue samples from the tumor under a microscope will show the same immunohistochemical characteristics of skin melanomas.
    