A Thymoma (Adenoma of the Thymus) from an Unusual Case of Myasthenia Gravis, with Observations on the General Pathology

Abstract

In 1936 I presented a report of four cases of myasthenia gravis, in two of which gross thymic lesions were found. At that time in a review of the literature only 80 cases of myasthenia gravis which had come to autopsy were found, and among these were 35 in which a lesion of the thymus constituted a prominent anatomic feature. It appears that progress toward a more exact understanding of myasthenia gravis has been largely hindered because of the small number of cases that have been studied by the pathologist. The importance of having recorded all cases of myasthenia gravis with definite pathologic findings I have previously emphasized. During the past year another case, which will be described here, came to my attention. Moreover, there was found a case reported by Löwenthal which had escaped notice and failed of inclusion in the tabulation in the earlier study; this case also is briefly summarized below. The addition of these 2 cases to those previously tabulated increases the total to 37 instances of thymic lesions in reported autopsied cases of myasthenia gravis. Case of Löwenthal, 1932: The patient was a sixty-three-year-old woman with severe muscular changes. At autopsy the thymus weighed 26 grams and measured 8 × 4.5 × 1.25 cm. Microscopically it had a lobulated structure but showed no differentiation of cortical and medullary zones. In some areas, however, a greater proportion of lymphocytes were present. Numerous Hassall9s corpuscles in various stages of development were found, and the author describes the development of pseudocysts from these.