Invasive thymoma

Case contributed by Dr Julian Maingard

Presentation

75 year old male presents with worsening dyspnoea on exertion. Pericardial effusion on transthoracic echocardiagram ordered by his local GP. CT imaging post pericardial drain insertion.

Patient Data

Age: 75
Gender: Male
Modality: CT

The heart is enlarged. There is a pericardial drain in situ. There is a small residual pericardial effusion measuring up to 1.9 cm in depth. There is a large lobulated mass in the anterior mediastinum, measuring 8.6 x 6.7 x 6.6 cm (transverse by AP by caudocranial dimensions). It is composed mainly of material of soft tissue density with small foci of calcification centrally measuring up to 1.2 cm. The mass probably invades the anterosuperior pericardium, and is closely related to the deepest pocket of the pericardial effusion. The mass also abuts the anterior surface of the left brachiocephalic vein, but does not cause significant compression.

There are small bilateral pleural effusions with minimal bibasal compressive atelectasis.

Case Discussion

Thymomas, while rare, are the most common primary tumours of the mediastinum 1. They arise from thymic tissue. Most patients are between 40 to 60 years of age with an annual incidence of 0.15 per 100,000 person years 1, 2. There is a strong association with myasthenia gravis and paraneoplastic syndromes2.

Histology 

Macroscopic:
Yellow adipose tissue 220 x 170 x 75 mm, 513 g, containing a firm multinodular tumour. On one side the specimen is lined by a shiny smooth membranous pericardial surface with multiple bulging exophytic brown nodules.

Sectioning reveals a variegated solid pale pink tumour 90 x 75 x 50 mm which extends to involve the roughened area of resection, together with multiple solid dark brown nodules up to 30 mm. No necrosis or haemorrhage is seen. The thymic fat shows yellow adipose tissue with several 5-10 mm tumour nodules immediately adjacent to the main tumour

Microscopic:
Invasive thymoma. WHO Types A & B3. 90 mm maximum dimension and incompletely excised. Involves chest wall inked resection surface over a distance of at least 10 mm. Tumour bulges into pericardial cavity but with intact pericardium. Lymphatic invasion identified. No perineural invasion identified.

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Case Information

rID: 31373
Case created: 4th Oct 2014
Last edited: 18th Dec 2015
System: Chest
Inclusion in quiz mode: Included

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