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The lump is unrelated to the stomach symptoms. It may be a possibility that after the biopsy
he has taken some analgesics which has precipitated gastritis
As such lump growing rapidly and doctor decided for a biopsy does not necessarily mean a malignancy for which you are worried. You have not mentioned the age of relative which could help me guide you better. However, best is to relax and wait for the biopsy.
Take care. Relax.