Imaging Findings
Study reveals a mediastinal mass
lesion with peripheral calcification and intense enhancement, and local
mediastinal invasion.
Histology following CT guided
FNAC
Thymoma
Discussion
Thymomas affect men and women with equal frequency, generally
afflicting adults above 40 years of age. Approximately 50% of thymomas are
discovered incidentally on radiographs in asymptomatic individuals taken
for other reasons. 25-30% of persons present with symptoms from
compression of adjacent mediastinal structures including the trachea,
recurrent laryngeal nerve, and esophagus. Sudden cardiac death due to
right artrial compression may occur. Thymomas may be associated with
myasthenia gravis, and other systemic disorders including pure red-cell
aplasia, hypogammaglobinaemia, endocrine, and connective tissue disorders.
These parathymic syndromes occur in 40% of patients with thymomas and
invasive thymomas occur in 30-40% patients.
Imaging Findings
Radiographs of chest reveal a contour abnormality of the anterior
mediastinum, as the mass displaces both visceral and parietal pleura,
resulting in smoothly marginated lobulated borders against the lung. They
may extend to both sides of the mediastinum or may arise in the
cardiophrenic angle. Calcification is common, is usually linear, thin and
peripheral.
CT
Replacement of the anterior mediastinal fat by denser soft tissue is
the primary sign. Thymomas appear as solid, oval or rounded homogenous
soft tissue masses, predominantly on one side of the midline, usually
bosselated/ lobulated, and in close relation to the root of the aorta and
pulmonary artery. Mediastinal involvement by thymomas is usually
intrathoracic and mostly pleural.
MRI
Multiplanar imaging is useful for thymoma evaluation. Thymomas are
usually iso intense on T1WI, with increased signal intensity on T2WI.
Malignant lesions have an inhomogenous signal, which may be related to
cystic/ hemorrhage within.
Staging
Masaoka Classification includes 5 stages, staging is usually performed
at the time of surgical intervention.
- No
capsular invasion
- capsular/pleural
invasion
- Invasion
of surrounding tissue (lung, pericardium, SVC)
4a.
Dissemination in the thoracic cavity (pleural & pericardial seedling)
4b
Lymphogenous and / or hematogenous spread
Stage 1
is non-invasive and stages 2-4b are invasive
Therapy
Surgical resection is the preferred treatment for patients. Total
thymectomy is recommended, and us associated with complete remission in
80-95% cases. Use of
radiotherapy is controversial, and is advocated as an adjunct to surgical
excision for cases of invasive thymoma, especially when only subtotal
excision has been performed. In recurrent/ metastatic tumor, chemotherapy
may play a limited role if at all (CAP regime of cyclophophamide,
cisplatinum & adriamycin).
Contribution
Dr. Sanjeev Mani, Mumbai
References
Yang WT, Metreweli C. Plain radiography & computed tomography of
invasive thymomas: Clinico-radiologic-pathologic correlation. Australas
Radiol 1997, 41: 118-124.
Crowe JK, Brown LR, Nuhm JR.
Computed Tomography of the Mediastinum. Radiology 1978; 128: 75-87
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