Patterns of metastasis and recurrence in thymic epithelial tumours: longitudinal imaging review in correlation with histological subtypes

Abstract

Aim: To determine the patterns of metastasis and recurrence in thymic epithelial tumours based on longitudinal imaging studies, and to correlate the patterns with World Health Organization (WHO) histological classifications.

Materials and methods: Seventy-seven patients with histopathologically confirmed thymomas (n=62) and thymic carcinomas (n=15) who were followed with cross-sectional follow-up imaging after surgery were retrospectively studied. All cross-sectional imaging studies during the disease course were reviewed to identify metastasis or recurrence. The sites of involvement and the time of involvement measured from surgery were recorded.

Results: Metastasis or recurrence was noted in 24 (31%) of the 77 patients. Patients with metastasis or recurrence were significantly younger than those without (median age: 46 versus 60, respectively; p=0.0005), and more commonly had thymic carcinomas than thymomas (p=0.002). The most common site of involvement was the pleura (17/24), followed by the lung (9/24), and thoracic nodes (9/24). Abdominopelvic involvement was noted in 12 patients, most frequently in the liver (n=8). Lung metastasis was more common in thymic carcinomas than thymomas (p=0.0005). Time from surgery to the development of metastasis or recurrence was shortest in thymic carcinoma, followed by high-risk thymomas, and was longest in low-risk thymoma (median time in months: 25.1, 68.8, and not reached, respectively; p=0.0015).

Conclusions: The patterns of metastasis and recurrence of thymic epithelial tumours differ significantly across histological subgroups, with thymic carcinomas more commonly having metastasis with shorter length of time after surgery. The knowledge of different patterns of tumour spread may contribute to further understanding of the biological and clinical behaviours of these tumours.

Fig. 1

A 35-year-old man with thymoma type B3. (a) Preoperative chest CT demonstrated a large anterior mediastinal mass with a lobulate contour, abutting the aortic arch and infiltrating the surrounding fat. The patient was treated with neoadjuvant chemotherapy and radical thymectomy. (b) Follow-up CT 22 months after surgery demonstrated a new pleural lesion on the left (arrow), which was surgically resected and histopathologically confirmed to be metastatic thymoma.

Fig. 1

A 35-year-old man with thymoma type B3. (a) Preoperative chest CT demonstrated a large anterior mediastinal mass with a lobulate contour, abutting the aortic arch and infiltrating the surrounding fat. The patient was treated with neoadjuvant chemotherapy and radical thymectomy. (b) Follow-up CT 22 months after surgery demonstrated a new pleural lesion on the left (arrow), which was surgically resected and histopathologically confirmed to be metastatic thymoma.

Fig. 2

A 44 year-old woman with myasthenia gravis and thymoma type B3, which was surgically resected. Follow-up chest CT after 69 months of surgery demonstrated an enlarged left supraclavicular lymph node, which was histologically confirmed as metastatic thymoma.

Fig. 3

A 33-year-old man with thymic carcinoma, treated with preoperative mediastinal radiation with concurrent cisplatin and etoposide, followed by radical thymectomy. Follow-up chest CT 5.3 months after surgery demonstrated a new nodule in the left lower lobe (arrow), which was subsequently resected and was pathologically confirmed as a metastasis.

Fig. 4

A 64-year-old man with thymic carcinoma. (a) Preoperative CT demonstrated a large anterior mediastinal mass with a lobulate contour abutting the pleura, with a focus of calcification (arrow). The patient underwent radical thymectomy followed by chest radiation with concurrent chemotherapy with two cycles of etoposide and cisplatin. (a) Follow-up chest CT 25 months after surgery demonstrated a new liver lesion in the left lobe (arrows). The liver biopsy was performed and metastasis from thymic carcinoma was confirmed.

Fig. 4

A 64-year-old man with thymic carcinoma. (a) Preoperative CT demonstrated a large anterior mediastinal mass with a lobulate contour abutting the pleura, with a focus of calcification (arrow). The patient underwent radical thymectomy followed by chest radiation with concurrent chemotherapy with two cycles of etoposide and cisplatin. (a) Follow-up chest CT 25 months after surgery demonstrated a new liver lesion in the left lobe (arrows). The liver biopsy was performed and metastasis from thymic carcinoma was confirmed.

Fig. 5

Time from the surgery date to the first scan demonstrating metastasis of recurrence in 69 patients with the detailed WHO classifications after excluding five patients whose metastasis persisted since baseline. The patients were classified into thymic carcinoma, high-risk thymoma (B3 and B2), and low-risk thymoma (B1, AB, A). The median time in months to metastasis or recurrence was 25.1 months, 68.8 months, and not reached, respectively (log-rank p=0.0015).