Case 1
This patient is a 64-year-old woman. She presented with vertigo for one month. Occasionally, her chest felt rather tight with shortness of breath and blurred vision. This patient had been weak lately, but her diet and sleep were normal.
The computed tomography (CT) scan showed that the chest was symmetrical and there was cord-like shadow in both lungs. Pulmonary micronodular lesions were detected in the upper lobe of the left lung; calcification could be seen in lower lobe of the left lung. There was a lobulated mass in the anterior mediastinum measuring 1.9 × 2.3 cm. The boundary was not clear, but no mediastinal lymphadenectasis. CT attenuation values were 57 Hounsfield units (HU). After enhanced scanning, CT attenuation values were 63 HU (Fig. 1a, b). The detection of 18F fluorodexyglycose positron emission tomography/CT (FDG-PET/CT) showed that there was no abnormal accumulation to indicate distant metastasis. A tumor 1.5 × 2.1 cm in size was completely resected. The postoperative pathology was diagnosed as thymic LELC.
Histologically, tumor cells were arranged in nest-like patterns or stripe-shaped infiltration in collagen fibrous interstitial tissue containing lymphocytes (Fig. 1c, d). The tumor cells had large vacuolated nuclei and irregular chromatin. Cell boundary was not distinctive, and the nucleus was crowded or overlapped. We can see the mitosis in nucleus (Fig. 1e, f).
Immunohistochemically, the tumor cells were diffusely positive for pan-CK (Cytokeratin AE1 + AE3), CK19 and EMA, as well as CD5 and CD117, while infiltrated B lymphocytes were positive for CD20. Positive nuclear expression of p63 was detected in the tumor cells. Ki67 index was about 20%. TdT was negative in tumor cells, as well as lymphocytes around tumor cells (Fig. 2). Above all, pathological diagnosis was thymic LELC.
The patient was treated with a chemotherapy regimen as following: Docetaxel (140 mg/m2, day 1) and carboplatin (500 mg/m2, day 1) every for four cycles, each lasting twenty days. At the same time, liver protection treatment was carried out. A subsequent clinical examination showed that there was no sign of tumor recurrence. After 3 years of follow-up, the patient was alive without tumor recurrence or metastasis.
Case 2
A 52-year-old male patient had the symptom of cough for four months and continued to worsen. Chest CT revealed an abnormal shadow. He came to our hospital and chest CT results showed a soft tissue density mass in the anterior mediastinum, measuring 9.55 × 4.86 × 5.3 cm. The boundary between the lesion and pericardium was not clear. CT attenuation values were 43 HU (Fig. 3a, b)..
Cut the sternum into the chest and excised the mediastinal tumor. The operation lasted 85 min and bleeding was 40 ml, while the tumor size was 9 × 5 × 2.5 cm. And the boundary with thymus tissue is not clear.
Postoperative pathology showed that the tumor cells were nests or cords, which was divided by fibrous septum and dense lymphocytes. The nuclei of tumor cells were empty and bright or hyperchromatic (Fig. 3c, d).
Immunohistochemical analysis revealed tumor cells were diffusely positive for pan-CK, CK19, CD5, CD117, EMA and p63, focally positive for CD20, and negative for TdT. Ki67 index was about 60% (Fig. 4). The detection of EB-encoded RNA in situ hybridization for the tumor was negative . Above all, pathological diagnosis was thymic LELC.
The patient was treated with radiotherapy 20 days after operation. And then he was treated with a chemotherapy regimen 1 month after radiotherapy: Etoposide (100 mg/m2, day 1-5) and cisplatin (30 mg/m2, day 1-3) every for four cycles, each lasting three weeks. A subsequent clinical examination showed that there was no sign of tumor recurrence. After 2 years of follow-up, the patient was alive without tumor recurrence or metastasis.