Mediastinal large B-cell lymphoma

Clinical History

Sixteen-year-old woman, presented to the Emergency Room with dyspnoea, asthaenia and dry cough for a week, without fever or expectoration. She reports the loss of 3 kg of weight in the last fifteen days and pain on the left arm, without loss of strength or sensibility.

Imaging Findings

The chest radiograph showed bilateral pleural effusion and widening of the anterosuperior mediastinum (Figure 1, 2).
Thoracic and abdominal computed tomography demonstrated a wide anterosuperior mediastinal mass with pleural and pericardial nodular implants, pericardial effusion and abundant pleural effusion, more evident on the right side. A left jugular vein thrombosed was identified. Some small retroperitoneal lymphnodes were also detected (Figures 3, 4, 5, 6 and 7).
A CT-guided percutaneous biopsy of the mediastinal mass was performed.
The diagnostic pathway was completed with brain CT, echocardiogram and sternal puncture.
The final diagnosis was mediastinal large B-cell lymphoma.

Discussion

Primary mediastinal large B-cell lymphoma is a sub-type of the category of large B-cell lymphoma, and constitutes approximately the 5% of all non-Hodgkin lymphomas (NHL). Typically it appears as an anterior mediastinal bulky mass, which frequently contains necrotic areas and has a locally aggressive behaviour [1, 2, 3].
In our case the differential diagnosis should be established with two other entities that involve the anterior mediastinum: thymoma and germ cell tumour.

Thymomas are solid neoplasms that occur sporadically or in association with myasthenia gravis, red cell aplasia, hypogammaglobulinaemia. Thymomas produce a distinct focal soft tissue density bulge along the normally smooth outer margin of the thymus or, when large, they totally replace the organ with a ovoid mass [4]. Approximately 15% are invasive. They may extend locally into adjacent mediastinal structures or implant along the pleural or pericardial surfaces. A widespread infiltration into the surrounding mediastinal fat or soft tissue masses along the pleural or pericardial surface are detected [4].
Rarely this neoplasm may grow directly into the lung. Thymoma is usually a tumour of the adult and it is rarely seen in children.

Extragonadal germ cell tumours usually appear between the second and fourth decade. Malignant tumours appear almost exclusively in men, they include seminoma and non-seminomatous germ cell tumours (embryonal carcinoma, tumours of the endodermic sinus, coriocarcinoma and mixed types).
Seminoma is a slow growing tumour and it appears as a large and homogeneous tumour. Malignant non-seminomatous tumours are aggressive large, ill defined masses, which can be associated to Klinefelter syndrome; they grow very quickly and most patients have symptoms of mediastinal structures invasion and metastatic disease when diagnosed.

Two subtypes of NHL are manifested as an anterior mediastinal mass: primary large B-cell lymphoma and lymphoblastic lymphoma. Large B-cell lymphoma involves patients among 10 and 45 years, mainly young women. It is an aggressive neoplasm, which rapidly reaches a large size (10 cm in 75% of patients) and usually involves other mediastinal organs as lung, pleura and pericardium, with associated superior vena cava syndrome in 50% of patients [1, 2, 3].
In both subtypes the lesion appears as a prevascular, large mass, with invasion of adjacent vascular structures, lung and chest wall, tracheal and oesophageal compression and pleural-pericardial effusion.

In our case the sex and age of the patient were very useful in order to establish the differential diagnosis among all these aggressive entities with a similar radiological appearance.

Differential Diagnosis List

Final Diagnosis

Mediastinal large B-cell lymphoma

URL:	https://www.eurorad.org/case/10547
DOI:	10.1594/EURORAD/CASE.10547
ISSN:	1563-4086