Pulmonary Pathology Online
Pathology of Primary Intrapulmonary Thymomas
intrapulmonary thymomas are defined as primary thymomas arising in an
intrapulmonary location without an associated mediastinal component, and
they are very rare.
Clinical examination reveals a parenchymatous intrapulmonary mass without evidence of mediastinal involvement either radiologically or at surgery.
Intrapulmonary thymomas are not associated with myasthenia gravis, unlike those of mediastinal thymoma.
Site: Close to the hilum ; Deep within the lung and in subpleural locations; May arise endobronchially and infiltrate the surrounding parenchyma.
Gross: Lesions vary from 0.5 to 10 cm in greatest diameter.
Systematic mediastinal lymph node dissection according to the lymph node map for primary lung cancer should be recommended for malignant cases.
Microscopic features: Histologically the tumour is composed of biphasic population of lymphocytes admixed with epithelial cells, with prominent lobulation and fibrosis.
Focal areas of spindling of the cells are noted in some cases.
In some cases there are prominent perivascular spaces.
A prominent granulomatous reaction has also been reported.
Immunohistochemical stains for keratin and epithelial membrane antigen highlight the epithelial cells scattered against the lymphoid cell background.
Immunohistochemical studies using lymphocyte markers may be an useful tool for the diagnosis of the thymoma of ectopic site or unusual presentation.
Treatment: Intrapulmonary thymomas are slow-growing tumors that may respond well to surgical resection when confined to the lung.
As with their mediastinal counterparts, invasive tumors will require additional treatment for the possibility of recurrence of metastasis.
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