Rationale:Suppression and of cancer metastasis is one of the most important issues in cancer care. Considering the typical clinical course of metastases, cancer cells might prefer certain environments or conditions. However, favorable environments for cancer metastasis have not been clearly identified. We had previously described a case of dual, yet separate, pancreatic and colon cancer, in which the metastatic pancreatic cancer was localized at the invasive portion of the colon cancer. We hypothesized that metastatic pancreatic cancer took over the colon cancer microenvironment.Patient concerns:We experienced an another case of double cancer in a 65-year-old man who had lung squamous cell carcinoma and an independent pancreatic adenocarcinoma that metastasized to the liver as well as to the lung cancer lesion and pulmonary fibrotic regions associated with pneumothorax and bronchiolization.Interventions:The pneumothorax could not be controlled by conservative treatment. Thus, an emergency surgery with partial resection of the lower lobe of right lung was performed.Diagnoses:We found multiple pancreatic cancer metastases in the lung cancer and fibrotic lesions in the surgical specimen. However, we detected no metastasis in normal lung tissues except inside small arteries, although the lung cancer and fibrotic tissue areas were smaller than the normal lung tissue areas in the surgical specimen.Outcomes:The patient died 50 days after the surgery.Lessons:This case may thus provide evidence to strengthen our hypothesis that pancreatic cancer prefers to metastasize to other independent cancer lesions, overtaking the cancer microenvironment constructed by other independent cancers. The lung cancer microenvironment, rich in myofibroblasts and/or cancer-associated fibroblasts, might be suitable for pancreatic carcinoma metastasis. In addition, we propose the hypothesis that compared with normal tissues, noncancerous fibrotic lesions are preferable destinations for cancer metastasis. Furthermore, metastasis of pancreatic carcinoma to lung cancer and fibrotic tissues might be more common, although such cases have not been previously reported.
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