"I was just sick to my stomach," she tells PEOPLE exclusively.
"I can't even begin to describe the feeling you get when someone says you have cancer," she says. "Then to get it again after you thought you fought it and thought it was behind you …."
"I was thinking, 'This is definitely it. I'm going to die.' "
Marchese, 37, was first diagnosed with cancer in her right breast in 2009. She says she chose to have a bilateral mastectomy even though her left breast was cancer-free – just to be safe.
On the last season of RHONJ, Marchese dealt with a cancer scare when blood tests for a cancer screening were initially inconclusive. In the end, she learned that she was, indeed, still cancer-free for the past five years.
All that has changed. The new tumor, she says, "is right in the middle of where the other two were. It's the same type of tumor.
After her 2009 Stage I diagnosis, Marchese thought chemotherapy and a double mastectomy would rid her of cancer forever, she says. "I thought, you remove it, you go through the harsh treatments, and you move on. So I was shocked. Everyone is shocked."
She says her doctor doesn't yet know if this is a brand-new tumor or if there wasn't enough breast tissue taken out with the mastectomy. "You're never going to remove 100 percent of the breast tissue with a mastectomy. So you just pray to God that you remove enough.
"You have a double mastectomy and chemotherapy to stack all the odds in your favor so that there is no recurrence. The percentage of it recurring is very small, less than 5 percent. I just fell into that category. I wasn't so lucky."
One thing she stresses: "This is not common. I want people to understand that. My case is not the average case.
"I don't ever want to deter women from getting a mastectomy. I don't want women to say, 'Well, she had a mastectomy. What's the point of getting a mastectomy if it doesn't work?
"That's a very dangerous message to get out. I hear it all the time. 'You got a double mastectomy. How did it not work?' My case is not the norm. Do what's right for you."
A Jolting DiscoveryMarchese discovered the lump on April 3 while watching a movie with her husband, Jim Marchese.
"I have no idea what made me do this, but I reached my arms over my head and touched my right breast and felt it. It was hard. It was pea-sized. And I just knew …. My heart just sank.
"I said, 'Jim, I just found another lump.' It was right by the site of the other tumors. I just knew in my heart that this was serious, and Jim did too.
When she saw her oncologist the following Monday, "He said, 'The odds of it being anything are so small. But I do want you to have it removed. I want a biopsy and a PET-CT scan right away.' This scared me because he did not say, 'I'm sure it's nothing.' "
When she had a PET-CT scan on April 13, she says, "The only thing that lit up was the tumor itself. That meant there is activity there."
She underwent a biopsy on April 20 to determine if the lump was cancerous. "On April 23, my surgeon called. I was making dinner for my kids. He said, 'Well, I wish I had good news for you, but it's not. It's cancer.' "
Aggressive TreatmentMarchese says her oncologist "is very hopeful" and does not believe the cancer has spread.
But he is taking no chances.
"I'm going to have an additional surgery to remove the remaining breast tissue with clean margins," she says. "I'm going to be on radiation five days a week for five weeks. The doctor is putting me on five different drugs, including Herceptin."
This week she will be getting an MRI of her brain and chest to make sure it hasn't spread, she says.
Hope and PrayerPraying has helped Marchese cope with her recurrence, she says.
"By God's good grace, I found the lump on Good Friday," she says. "I have spent a lot of time in prayer. It's the only thing that is giving me a sense of hope that no matter what, everything is going to be okay. It takes away my fear and doubt.
"Then you kind of just take a deep breath and you just talk. Jim and I talked this through every which way, probably 24/7. And we pray. We pray together. We pray by ourselves."
She says she prays anytime she gets upset or thinks negative thoughts. "Once I pray, it's such a comfort. It's like a blanket – like God is wrapping his arms around you and is saying, 'It's going to be okay. Don't get caught up in these worldly fears. I have you.' "
One of the biggest lessons she's learned? "How to stay calm and be in the moment and just enjoy the present. I go 150 miles per hour all the time. I'm learning to slow myself down."
She is continuing with her regular routines. "I have children, and my children can't see worry on my face. They can't see me skip a beat. They still need me."
She says, "Jim and I will go to the gym, then we'll go have radiation, come home and have lunch and have a good day. That will be our new normal for a while – we will adapt, improvise and overcome.
"You just have to go on with everyday life. I always say, it's not a matter of if something is going to happen, it's a matter of how we handle it. I feel at peace. I feel determined. I feel like everything is going to be okay."