Presentation
Subacute presentation of fatigue, chest discomfort and dyspnea.
Patient Data
There is a large anterior mediastinal mass spanning a craniocaudal length of at least 10 cm causing tracheal deviation to the right. Differentials include teratoma, thymic neoplasm and lymphoma. No large regions of airspace consolidation or atelectasis. No pleural effusion. No pneumothorax. No bony lesions or fractures.
There is a large ovoid anterior mediastinal mass measuring 11 x 9 x 9 cm (transverse x anteroposterior x craniocaudal) to the left of the midline, heterogenous in appearance with lobulated fat density components and several small calcific foci. Marked internal vascularity demonstrated.
The mass is anterosuperior to the heart with pronounced mass effect upon the right ventricular outflow tract (RVOT), pulmonary trunk and left main pulmonary artery (LPA). RVOT orifice is narrowed to 7 x 31 mm. Ostial LPA is narrowed to 17 x 3 mm.
The tracheobronchial tree is patent, however there is marked mass effect involving the left main bronchus (narrowed to 3 mm AP). Close relationship between the inferior mass and the RVOT pericardium with loss of the normal fat plane. There is a pericardial effusion visualized at the cardiac apex. No nodularity of the pericardium identified.
Left lower lobe bronchial thickening with tree in bud nodularity adjacent in the medial basal segment suggests inflammatory change, possibly due to aspiration. No focal pulmonary lesion or mass. No focal filling defect to suggest pulmonary embolus on this non dedicated imaging.
Partially obscured two small ovoid solid structures adjacent to the mass superiorly and appear hyperdense possibly representing lymph nodes and measure 16 mm and 12 mm short axis respectively. No evidence of further mediastinal or axillary lymphadenopathy. No abnormalities of the partially imaged abdomen.
Features are suspicious for germ cell tumor/mediastinal teratoma, differentials include thymolipoma.
Case Discussion
A diagnosis of non-seminomatous germ cell tumor was made on the basis of elevated AFP and BhCG and imaging findings. The patient proceeded to undergo treatment without a biopsy which consisted of 4 cycles of neoadjuvant chemotherapy followed by surgical resection of the mass. The histology revealed mature teratoma with clear margins and no evidence of metastasis, indicating the treatment had been successful in achieving remission.
Histology:
The sections show a well-circumscribed mature teratoma of the mediastinum surrounded by a fibrous capsule of variable thickness. The tumor has a multicystic appearance and is composed of multiple cystic spaces lined by squamous epithelium and cutaneous adnexal structures with luminal keratinized debris, spaces lined by ciliated respiratory-type epithelium and intervening cartilage, smooth muscle, adipose tissue and a small amount of neuroglial tissue. No immature neuroepithelial elements are identified and no other immature elements are seen within the teratoma. No other viable germ cell tumor type is identified within the lesion. There is no evidence of somatic malignancy arising within the teratoma. There has been minimal response to the neoadjuvant chemoradiation with only focal necrosis identified. The teratoma is adherent to but does not invade into the mediastinal pleura or the pericardium. The tumor appears clear from the surgical resection margins. Adjacent thymic tissue shows no significant pathologic features. Four peri-thymic lymph nodes have been identified and exhibit mild reactive changes.
Summary:
Anterior mediastinal mass:
encapsulated mature teratoma, 110 mm in size
minimal response to the neoadjuvant chemoradiation
the tumor appears clear from the surgical resection margins
no evidence of metastasis or treatment effect within four peri-thymic lymph nodes
The elevated serum AFP at the time of initial diagnosis is noted. The tumor has been extensively sampled and no viable yolk sac tumor or germ cell tumor type other than mature teratoma is identified in the resection specimen. There is no agreed-upon staging system for mediastinal teratoma.
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