Thymic carcinoma

Case contributed by Dr Henry Knipe

Presentation

Cough. Otherwise well with no relevant past medical history.

Patient Data

Age: 70 years
Gender: Male
X-ray

Lobulated right cardiomediastinal contour, confirmed as an anterior mediastinal mass on the lateral projection. Lungs are clear. Cardiac silhouette is not enlarged. No destructive bone lesion. 

CT

Lobulated enhancing anterior mediastinal mass abutting great vessels and major veins. Prominent vessels within and around the mass. No pulmonary or pleural masses. No hilar, axillary or upper abdominal lymphadenopathy. 

Nuclear medicine

The mass demonstrates intense avidity with a SUV max of 11.5. Avidity elsewhere is within physiological limits with no evidence of lymphadenopathy or distant spread. 

Pathology

An irregular piece of soft yellow fatty tissue 487 g, 245 x 175 x 60 mm containing a well demarcated rubbery tan-pink tumour 92 x 62 x 57 mm. Tumour extensively abuts surrounding capsule, however capsular invasion is not identified. Tumour also infiltrates into surrounding fatty tissue. 

Courtesy of Dr Alpha Tsui, pathologist, The Royal Melbourne Hospital. 

Pathology

Sections show an encapsulated tumour comprising sheets of epithelial cells separated by dense fibrous septa. Tumour cells have pleomorphic ovoid nuclei, cleared chromatin and prominent nucleoli. Tumour nests contain scant lymphocytes and scattered mitoses are seen. Necrosis, marked atypia, intercellular bridges and keratin pearls are not seen. A focus of capsular invasion is present and tumour focally extends to the margin. Lymphovascular and perineural invasion are not seen. In the surrounding fat, there is a lymph node with no evidence of malignancy. Tumour cells show positive staining with CK5/6, p40, c-kit, CD5 and focally with CK7. TTF1 is negative and tumour lacks TdT positive lymphocytes. 

Courtesy of Dr Alpha Tsui, pathologist, The Royal Melbourne Hospital. 

Case Discussion

The final diagnosis of this anterior mediastinal mass is thymic squamous cell carcinoma (thymic carcinoma). On imaging the differential diagnosis is that of anterior mediastinal masses - thymoma, lymphoma, or germ cell tumour, with the latter unlikely given the patient's age. Differentiating thymoma from thymic carcinoma is only readily done when there is evidence of local invasion or metastatic disease. 

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Case information

rID: 47773
Case created: 2nd Sep 2016
Last edited: 18th Mar 2017
Systems: Chest, Oncology
Inclusion in quiz mode: Included

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