CHICAGO (CBS) — Going over medical bills can be complicated, but that is exactly what patients at one Chicago area hospital have been told to do.

As CBS 2’s Jermont Terry reported Wednesday night, this comes after their medical information was potentially made vulnerable to hackers.

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“My information’s out there,” said Anthony Stroccio. “I don’t know who has it.”

There is legitimate concern for Stroccio. He received an ominous letter this week from Northwestern Medicine.

It the possibility that information about his health is part of a security breach involving Elekta, a company which does cancer reporting for the State of Illinois.

“My information wasn’t safe,” Stroccio said.

Back in April, Elekta first acknowledged the breach – which included some of Northwestern Medicine’s oncology patients, like Stroccio.

“When you said this happened back in April and it’s still – I just got the letter now,” he said.

Yet Northwestern Medicine said Elekta did not let them know its patients were part of the hack until mid-May.

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The hospital stresses there was never a breach in its network – only the data Elekta gather from cancer information for the state. Yet Stroccio is not a cancer patient.

“Going for every two weeks for the chemo – but not because it’s cancer. It’s just the only way they can treat my growing tumor,” he said.

Stroccio’s tumor is benign, and he trusted his medical bills before getting that letter. Now, he is told, “I should check my billing from my insurance provider to make sure it’s correct.”

Medical bills arrive weekly from his ongoing treatment. He is now left with a bigger headache.

“It’s really cumbersome to try and itemize them all; to go through the list,” Stroccio said.

Stroccio’s letter advised him also to check his credit report. But get this – he said his deceased brother-in-law received the notification, and yet, “They offered him a one year of credit monitoring and I didn’t get offered that.”

Northwestern Medicine insisted that no Social Security numbers or financial information were compromised. The hospital would not say how many patients received the letters. But they set up a special call center to address patient concerns.

This is the full statement from Northwestern Medicine:

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“We regret this incident occurred and we are committed to protecting the security and privacy of patient information. This incident did not involve access to any of the Northwestern Memorial Healthcare systems, network, or electronic health records. This incident occurred on Elekta’s systems. Based on the nature of the incident and its investigation, Elekta has no reason to believe that any of the data involved was or will be misused or will be made available publicly. We are encouraging our oncology patients to review statements from their health insurer or healthcare provider, and to contact them immediately if they see any services they did not receive. We have established a dedicated call center to answer questions about this incident, at (855) 731-3327, Monday through Friday, from 9 am to 5:30 pm CST.”