A 70-year-old woman presented to the outpatient service in our hospital because of continuously elevated carcinoembryonic antigen (CEA) levels detected during a routine examination (from 9.43 to 28.02 ng/ml) for 10 months without any symptoms. During this period, no sign was found on abdominal CT and colonoscopy. To clarify the source of CEA, PET/CT was arranged for this patient. The examination revealed effusion in the oblique fissure of the left lung, and nodular thickening (standard uptake value (SUV) = 2.08) was also present near the pleura in the lower lobe of the left lung (Figure 1A). The lesion size was 7 x 3 x 1 cm3. In addition, a cystic mass (Figure 1B) was located in the ileocecal area, and the SUV at the edge of the mass was 2.28. The patient consulted a thoracic surgeon. The thoracic surgeon organized a multidisciplinary team (MDT) to formulate plans for treatment, including our treatment team. After discussion, the patient and her family were consulted, and the final treatment plan was determined: two surgeries were successively arranged for the pulmonary tumor and ileocecal tumor.
The pathologic analysis of the pulmonary tumor revealed mucinous neoplasms (Figure 1C). Immunohistochemistry disclosed positivity for CK7 and CK20 and negativity for napsin A, TTF1, and SATB2, which confirmed that the pulmonary tumor was metastatic adenocarcinoma. Therefore, we decided to perform right hemicolectomy for her. Because the patient suffered a pulmonary infection after the thoracic surgery, the abdominal surgery was not performed until 3 months. However, postoperative pathology revealed a LAMN but not mucinous adenocarcinoma (Figure 1D).
After the H&E staining of two tumors was reviewed, it was found that both tumors harbored low-grade cytology and a "push" growth pattern. To further clarify the relationship between tumors, NGS was performed for this patient. Tumor cells from sections of the tumors were accurately collected under a microscope for NGS because of the small number of tumor cells in the mucinous neoplasm (Figure 2A). The results illustrated that both tumors carried the same tumor-specific mutations, namely, KRAS (p.G12D), GNAS (p.R201H), and BRAF (p.R735Q) (Figures 2B, C), which indicated that the pulmonary tumor was a metastasis of LAMN.