A 67-year-old female patient was admitted to the local hospital because of epigastric pain and discomfort for one month. She was diagnosed as a malignant tumor of the gastric body by electronic gastroscopy and biopsy pathology. The abdominal enhanced CT shows multiple lymph nodes enlargement in the abdominal and retroperitoneum in the outpatient clinic of our hospital ( Figures 1A, B  ). The patient received six cycles of chemotherapy in another hospital (SOX regimen for 1 cycle; S-1 and oxaliplatin. Paclitaxel, oxaliplatin, S-1, and Sintilimab for 5 cycles). After the end of chemotherapy, the effect of chmotherapy was evaluated as partial remission (PR). The patient asked for surgical treatment in our hospital. Physical examination showed that the abdomen was flat, the abdominal muscles were soft, the upper abdomen was mild deep tenderness, there was no rebound pain, and there was no obvious abdominal mass. Laboratory results showed that hemoglobin content decreased: 97g/L (normal range 110-150g/L). CA72-4:4.90U/mL (normal range 0-6.9U/mL), AFP: 1.30ng/mL (normal range 0-8.1ng/mL), CEA:1.13ng/mL (normal range 0-10ng/mL), CA199:17.71U/mL (normal range 0-37U/mL), CA125:2.85U/mL (normal range 0-30.2U/mL). There was no significant increase in serum tumor markers. After the end of neoadjuvant chemotherapy, we performed a PET-CT examination for the patient. 18F-FDG PET-CT showed that the mass showed changes after chemotherapy, slight thickening of the lesser curvature of the stomach, the mass did not significantly absorb FDG, and it was found that the left axillary lymph node was enlarged, and the mass uptake of FDG increased slightly, but it was considered as an inflammatory lesion ( Figures 1C ). After multidisciplinary tumor consultation, we decided to perform the radical total gastrectomy on the patient, and regular examination of the enlarged lymph nodes in the left axilla. After obtaining the consent of the patient and her family, the patient underwent radical total gastrectomy (Roux-en-Y digestive tract reconstruction) in August 2021. Postoperative pathology showed that the area of ulcerative gastric cancer was about 4 x 3cm. The main tumor cells were poorly differentiated adenocarcinoma, local invasion of the deep muscular layer of the gastric wall, and tumor cells can be seen in the lymphatic vessels but no definite nerve invasion. Lauren's classification was the diffuse type ( Figure 2A ). Only one of the 21 lymph nodes had metastasis, which was located on the lesser curvature of the gastric wall, and no obvious tumor metastasis was found in the rest of the lymph nodes (ypT2N1M0 IIA). Immunohistochemical staining showed that tumor cells expressed CK8/18, individual cells expressed Syn, and did not express CgA, CD56, SALL4, Oct3/4, C-erb-B-2, and Ki-67 proliferative index was approximately 90%. The patient recovered smoothly without obvious postoperative complications and was discharged 13 days after radical total gastrectomy.
One month after radical total gastrectomy, the patient found that the left axillary mass grew faster than before and was accompanied by the limitation of left upper limb movement. Physical examination showed that the left axillary mass was about 4 x 2cm in size, hard, had an unclear boundary, and had a poor range of motion. Ultrasound examination of the bilateral breast and axilla showed that there was no obvious mass in the bilateral breast, and several hypoechoic lesions were found in the left axilla, the size of which was about 4.3 x 1.9cm, the boundary was clear, the cortex was thickened, the medulla was eccentric and the blood flow signal was abundant ( Figure 3A ). No obvious abnormality was found in mammary gland molybdenum target X-ray ( Figures 3B, C  ), mediastinal and supraclavicular enlarged lymph nodes were not found in CT, and no obvious bone metastasis in whole-body bone scintigraphy ( Figure 3D ). The patient underwent the axillary lymph node biopsy in October 2021. During the operation, the enlarged lymph nodes were located next to the axillary vein, fused into clumps, hard texture, and closely combined with the surrounding tissues. Intraoperative frozen sections showed that there were 5 lymph nodes in the left axilla, and all of them had cancer metastasis. After that, we performed radical axillary lymph node dissection and 14 of the 18 lymph nodes had metastases. Pathology showed that the tumor cells were poorly differentiated adenocarcinoma. immunohistochemical staining showed that most of the tumor cells expressed Caudal-type homeobox 2 (CDX2), CK20, GATA binding protein 3 (GATA-3), and a small amount of sequence-binding protein (SATB) 2 and Mucin-5AC (MUC5AC), but no expression of CK7 and TTF-1 was found ( Figures 2B-E ). After communicating with pathologists, considering the immunohistochemical results and the history of gastric cancer, we considered that the left axillary lymph node tumor was metastasized by gastric cancer.
The patient received docetaxel and fluorouracil chemotherapy after radical axillary lymph node dissection, and a progressive increase in CEA, CA19-9, and CA72-4 was found (  Figure 4  ). Three months after the second operation, the MR examination of cervical and thoracic vertebrae due to back pain revealed secondary malignant tumors of the spine, but the patient refused to undergo whole-body bone imaging. CT of the chest and abdomen showed double clavicular and mediastinal enlarged lymph nodes, considering the malignant tumor. But the patient refused any treatment and died 11 months after the second operation.