Hello. I would be happy to try to answer your question.
I understand how this can be confusing for you, as it is for many pathologists.
IPMN is a precancerous lesion with a well described adenoma carcinoma sequence. However, the rate of progression appears to be extremely slow (approximately 15 to 20 years). As many as 70% of main duct type intraductal papillary mucinous neoplasms
harbor high-grade dysplasia (the step right before an invasive cancer develops) or an invasive cancer. Main duct type IPMNs are therefore significant lesions, and, in general, most main duct intraductal papillary mucinous neoplasms should be surgically resected if the patient can safely tolerate surgery.
Therefore IPMN is NOT benign. It is precancerous. The cells of your second opinion are the cells that are there in a normal pancreas. IPMN cells have taken the next step, so to speak, towards malignancy. There is no way for me to know what you have without seeing the pathology slides personally. You may wish to seek a third opinion given that the two opinions you have do not agree.
IPMN has most commonly been described in individuals between the ages of 60 and 70 years, most of whom have a long-standing history of recurrent acute pancreatitis or symptoms suggestive of chronic obstructive pancreatitis due to intermittent obstruction of the pancreatic duct with mucus plugs.
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Take good care, and best wishes.