Granulomatous thymoma or Hodgkin's disease of thymus?:A clinical and histologic study and a re-evaluation

Lesions of the thymus called “granulomatous thymoma” or “Hodgkin's thymoma” are well known, but their histogenesis and relation to Hodgkin's disease have been subject to controversy. In this study, 24 of these lesions were selected from a larger group originally diagnosed as granulomatous thymomas, using the following criteria: 1. the presenting lesion involved the thymus, but not the mediastinal or peripheral lymph nodes. 2. the “granulomatous” component resembled that of the nodular sclerosing form of Hodgkin's disease, even though the Reed-Sternberg cells were often atypical, often contained PAS positive material, and often appeared to arise in or from thymic epithelium. 3. the thymic epithelium participates in the process by producing sheets of squamoid cells and/or cystic structures lined with columnar cells. 4. In the centers of the “nodular sclerosing” foci, there is often a Hassal's corpuscle or some other focus of thymic epithelium. Of 17 patients treated, ten were apparently free of disease from 2 to 9 years after the onset of the illness. Six patients developed extrathoracic lesions which, by and large, were either typical of Hodgkin's disease or acceptable as a mixture of classical Hodgkin's disease and pleomorphic reticulum cell sarcoma. Radiation therapy alone, or associated with surgery, appeared to be a better treatment than surgery alone. There was no detectable histologic difference between those cases which eventually resulted in disseminated disease and those that did not. These clinicopathologic correlations suggest that granulomatous thymoma, as defined above, is basically a peculiar manifestation of Hodgkin's disease, primarily involving the thymus and eliciting in it a unique tissue response.