Presentation
Cough. Otherwise well with no relevant past medical history.
Patient Data
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.
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.
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.
An irregular piece of soft yellow fatty tissue 487 g, 245 x 175 x 60 mm containing a well demarcated rubbery tan-pink tumor 92 x 62 x 57 mm. Tumor extensively abuts surrounding capsule, however capsular invasion is not identified. Tumor also infiltrates into surrounding fatty tissue.
Courtesy of Dr Alpha Tsui, pathologist, The Royal Melbourne Hospital.
Sections show an encapsulated tumor comprising sheets of epithelial cells separated by dense fibrous septa. Tumor cells have pleomorphic ovoid nuclei, cleared chromatin and prominent nucleoli. Tumor 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 tumor 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. Tumor cells show positive staining with CK5/6, p40, c-kit, CD5 and focally with CK7. TTF1 is negative and tumor 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 tumor, 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.