Brief Answer:
This may be the sign of pancreatitis as explained

Detailed Answer:
Hi.
Thanks for your query.
Noted the history about being treated for pancreatitis and developed a dark blotch with white center on stomach.
The most probable cause I can think about with your short history is as follows:
Pancreas is the gland that produces the enzymes that help in digestion of all sorts of food one takes. Pancreas is situated in the retro-peritoneal area that is behind the peritoneum and hence when inflamed with leakage of enzymes, these can reach the abdominal wall and give a dark blotch.
Other causes can include coagulopathy and so on to be confirmed or ruled by appropriate investigations.

In short this may most probably due to pancreatitis itself.

I hope this answers your query.
Please post clear and focused photos of affected area as this may help for proper diagnosis and correlation with diagnosis.

With Regards.
Dr T Chandrakant
General Surgeon.

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