PAMELA AGUILAR MARÍN, Radiologist.
REGIONAL HIGH SPECIALITY HOSPITAL OF CIUDAD VICTORIA
A 19-year old man presented a 1-month history of chest pain, 6/10 intensity and irradiated to the face which progressively increased until presenting a subital painful crisis with 9/10 intensity, accompanied by progressive dyspnea (NYHA II-III), chest tightness and gastric fullness with little food intake. He also refered 8 kg weight loss in a month.
The respiratory impairment continued with tachycardia and otyhopnea, so he attended the emergency department for clinical assesment.
A heterogeneous mass infiltrating the pericardium, myocardium and the proximal ascending aorta and pulmonar artery was observed. Vascularity of the mass was seen with Doppler . LV FE 74%.
Alpha-fetoprotein, human chorionic gonadotropin (hCG) and beta-2 microglobulin negatives.
Figures 1 and 2.- Chest CT scan (mediastinal window). Homogeneous
lesion in anterior mediastinum with lobed edges, displacing the mediastinal structures to the right.
Figures 3 and 4.- Chest CT scan (lung window). Alveolar occupation and air bronchogram in the left upper lobe, as well as bilateral reticulonodular pattern.
Figures 5 and 6.- Contrast-enhanced chest CT scan. Lesion involving large vessels and displacing structures to the left. It presents heterogeneous enhancement to the passage of contrast.
Figures 7 and 8.- Axial and coronal HASTE sequence chest magnetic resonance imaging (MRI). Mass displacing the main pulmonary artery to the left is observed, it involves the great vessels and predominately the right cardiac chambers.
Figure 9.- T2 MRI and Figure 10.- T2 FS MRI, both showing a heterogeneous mass and hiperintensity regions.
Figures 12 and 13.- Contrast-enhanced MRI and y magnetic resonance angiography (MRA).
Heterogeneous uptake of paramagnetic contrast is observed with cystic areas. MRA shows collateral vessels and asymmetry of the pulmonary vasculature.
Mediastinal tumors affect people of all ages (frequency < 50y) . They have a big variety in histology and may be either primary tumors or metastases. Malignant tumors occur in approximately 42% of all cases, being the neurogenic lymphoma and germ cell tumors the most frequent.
Imaging studies are useful to determine the location, extent and characterization of the tumor. Chest radiography is used to locate and size the tumor. Computed tomography can define the characteristics of the lesion with the tumoral attenuation degree (measured in Hounsfield unit, UH) and the contrast uptake :
Fat attenuation ( -70 to -100UH ): benignity.
Low attenuation ( -20 to +20 HU ): cysts or tumors with cystic degeneration.
High attenuation ( > 60UH ) : calcium structures or blood.
Contrast medium uptake : vascular structures.
MRI is excellent to assess areas of complex anatomy and its extension and infiltration, it provides information about the composition of the mass, differentiating between cystic and solid lesions, their degree of vascularization and to distinguish residual tumor tissue from fibrous tissue scarring. It also helps to obtain indicative signs of benignity or malignancy and sometimes to determine the nature of the injury.
The basic sequences to study the mediastinal masses are T1-weighted sequences that help to highlight various components such as fat, melanin or methemoglobin and T2-weighted sequences, in which the greatest signal strength occurs in structures with high water content. Pulses can be added to these sequences to intended to remove fat.
The use of contrast sequences, can help to determine the degree of vascularization of the mass. Vascular tumors such as hemangioma or angiosarcoma fill quickly with contrast and display a high signal intensity and these sequences often allow to better define the boundaries of the tumor, due to the increased vascularization in contrast with the other adjacent structures.
Moreover, these images can detect areas with intramural necrosis and cystic or calicified zones, seen as hypointense regions.
Pérez David Esther. Utilidad de la resonancia magnética en el estudio de las masas cardiacas y la afección pericárdica. Rev. Esp Cardiol Supl. 2006:6 (E): 30-40
Kim JY, Tumors of the Mediastinum and Chest Wall, Surg Clin N Am 90(2010)
A Diagnostic Approach to Mediastinal Abnormalites RadioGraphics vol 27 No 3 2007