Does my mom really have cancer?

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My mom had a stroke and then about a week later she had a heart attack. The doctors were saying she might have lupus. Then they said antiphospholipid syndrome. My mom was sent for a second opinion and the doctors took a needle biopsy from one of her lymphnodes in her neck. The results came back as squamous cell carcinoma - in the lung. They do not see anything in her lungs. They have checked all the other places that squamous cell could be and there was nothing. Could they be wrong?