A 65-year-old man visited our hospital for treatment of colon cancer in June 1998. Elevated serum carcinoembryonic antigen (CEA, 17.0 ng/dL; normal range, 0-5 ng/dL) was found at the time of diagnosis. Colonoscopy revealed a type 2 tumor in the sigmoid colon. Computed tomography (CT) showed a T3 tumor in the sigmoid colon with multiple lymph node metastases (cT3N2bM0 cStage IIIc). In September 1998, we performed extended left hemicolectomy (D3 dissection) and para-aortic lymph node dissection. Histological examination revealed moderately differentiated adenocarcinoma invading the muscularis propria without exposure on the serosal surface (n 2b, ly 2, v 1). Metastasis to the para-aortic lymph nodes was also found. After surgery, the patient’s serum CEA level normalized. Adjuvant chemotherapy with tegafur-uracil (100 mg/m²) was given to the patient for 4 years until 2003.

In February 2007, the patient’s tumor markers were normal but CT showed a tumor in the lower mediastinum. The tumor was 16 mm in size and located in the retrocrural space with suspicion of enlarged lymph nodes (Figure 1). CT, magnetic resonance imaging (MRI), and positron emission tomography-CT (PET-CT) did not identify any other primary cancer or any other site of recurrence, such as distant organ or locoregional recurrence. We considered that the tumor was probably a solitary recurrence of the colon cancer and planned a surgical resection because the tumor had enlarged over 3 mo.

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Figure 1 The tumor was 16 mm in size and located in the retrocrural space with suspicion of enlarged lymph nodes. A: Computed tomography (CT) scan showing a 16-mm tumor in the retrocrural space of the lower mediastinum; B: Positron emission tomography-CT did not reveal any other abnormal accumulation. The mediastinal mass had 4.232 of the sum of the maximum standard uptake values. SUV: Standardized uptake value.

In May 2007, the patient underwent surgical resection of the tumor. We decided against a laparotomy, but performed a left thoracotomy to avoid adhesion due to the previous operation. After thoracotomy, the tumor was identified on the right-anterior surface of the descending aorta. The tumor was easily separated from neighboring organs, such as the aorta or vertebrae, but had extensively invaded the thoracic duct. Therefore, we resected the thoracic duct along with the mediastinal tumor. Histopathology revealed the widespread metastasis of moderately differentiated adenocarcinoma accompanied by necrosis, and it was diagnosed as mediastinal metastases of colon cancer (Figure 2).

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Figure 2 Histopathology revealed the widespread metastasis of moderately differentiated adenocarcinoma and necrosis. Hematoxylin and eosin stain, A: × 10, B: × 50.

The patient was given adjuvant chemotherapy with S-1 (100 mg/m²) and irinotecan (115 mg/m²) for 6 mo. He is doing well with no recurrence for 6 years after the surgery for the recurrent tumor.

In November 2004, a 50-year-old man was admitted to our hospital for treatment of rectal cancer. Colonoscopy revealed a tumor that occupied the entire circumference of the rectum (type 2). Pre-operative CT and MRI showed a T3 tumor in the rectal colon with multiple lymph node metastasis (cT3, N2b, M0 cStage IIIc). In January 2005, we performed para-aortic lymph node and lateral lymph node dissection, in addition to low anterior resection (D3 dissection). Histological examination revealed moderately > poorly differentiated adenocarcinoma invading the muscularis propria without involvement of the serosa (n 2b, ly 0, v 0). Metastasis to para-aortic and lateral lymph nodes was also found. After surgery, the patient’s tumor marker normalized (serum CEA 80.9 ng/dL to 3.5 ng/dL). Three regimens of adjuvant chemotherapy were carried out for 18 mo. The first regimen was irinotecan (100 mg/m²), levofolinate (250 mg/m²), and fluorouracil (500 mg/m²) for 6 mo, the second was S-1 (80 mg/m²) and irinotecan (80 mg/m²) for 4 mo, and the last was S-1 (120 mg/m²) for 8 mo.

In January 2013, we noted swelling of a para-esophageal lymph node on CT (Figure 3) and elevation of serum CEA (19.0 ng/dL). We performed an endoscopic ultrasound-guided fine-needle aspiration biopsy and diagnosed mediastinal metastasis of rectal cancer. No other site of distant metastasis or local recurrence was found. The patient complained of dysphagia. Therefore, we considered that the tumor was a solitary recurrence of the rectal cancer and decided to perform tumor resection.

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Figure 3 Computed tomography scan showing swelling of a para-esophageal lymph node (A), positron emission tomography-computed tomography did not reveal any other abnormal accumulation (B). The mediastinal mass had 4.520 of the sum of the maximum standard uptake values. SUV: Standardized uptake value.

In March 2013, using video-assisted thoracic surgery, we resected the mediastinal tumor, lower esophagus, and thoracic duct, because the tumor located in the posterior mediastinum had widely invaded the right side of the esophagus and thoracic duct, and performed reconstruction with a subtotal gastric tube. Histopathology revealed no neoplastic change in the esophageal mucosal surface, compression from the esophageal adventitia, or infiltration of the muscularis propria (Figure 4). Immunohistochemical analysis showed that the metastatic tumor was positive for cytokeratin (CK) AE1/AE3, CK20 and caudal-type homeobox transcription factor 2 (cdx-2) and negative for CK7, confirming that it was metastasis from rectal cancer.

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Figure 4 Histopathology showing no neoplastic change in the esophageal mucosal surface, compression from the esophageal adventitia, or infiltration of the muscularis propria. Hematoxylin and eosin stain, A: × 10, B: × 50.

Adjuvant chemotherapy was not given because the patient did not want it. He is doing well with no recurrence for 4 mo after the surgery for the recurrent tumor.

A 65-year-old male and a 50-year-old male with a history of resected colon cancer had no symptoms.

Clinical findings were not particular.

Esophagus cancer, metastasis of head and neck cancer or urological cancer, mediastinal tumor.

Tumor markers were normal in case 1 and serum carcinoembryonic antigen elevated 19.0 ng/dL in case 2.

Positron emission tomography/computed tomography scan showed lower mediastinal mass (16 mm) with standardized uptake value (SUV) of 4.232 in case 1 and a para-esophageal lymph node with SUV of 4.520 in case 2.

Histopathology revealed the widespread metastasis of moderately differentiated adenocarcinoma in case 1 and immunohistochemical analysis showed that the metastatic tumor was positive for cytokeratin (CK), AE1/AE3, CK20 and caudal-type homeobox transcription factor 2 and negative for CK7, confirming that it was metastasis from rectal cancer in case 2.

After surgical resection, the patient in case 1 was given adjuvant chemotherapy with S-1 (100 mg/m²) and irinotecan (115 mg/m²) for 6 mo and the patient in case 2 was not given adjuvant chemotherapy.

Mediastinal lymph node recurrence is very rare and only two cases have been reported thus far. One was a combined recurrence in an ovary and mediastinal lymph node, and another was solitary mediastinal lymph node recurrence.

Retrograde lymph node metastasis occurs via the thoracic duct from a retroperitoneal lymph node. Hematogenous metastasis occurs via the paravertebral venous plexus.

Patients should be followed up after colon cancer surgery considering the possibility of solitary mediastinal lymph node recurrence if they had para-aortic node metastasis at the time of initial surgery.

This article highlights a rare entity, metastatic solitary mediastinal lymph node after resection of colon cancer in the form of two cases.