BACKGROUND: To detect and quantify myoid cells in thymus of patients with myasthenia gravis, establishing possible correlation between the amount of myoid cells and demographics, clinics, and pathological variables. METHODS: thymic specimens of 22 patients (16 women and six men, age ranging from 12 to 61 years, were analyzed through immunohistochemistry with monoclonal antibody anti- desmin (Dako - D33). They were submitted to tymectomy, between 1981 and 1995, in the Thoracic Surgery Department of Hospital Heliópolis, São Paulo, Brazil, as part of the treatment for myasthenia gravis. RESULTS: The largest mean valves of myoid cells were found in the thymus of patients from the black race (29.4: 17.8), female (23,2: 13,0) and with ages between 60 and 80 years old (average of 33.0) years old according to the the clinical classification of the Myasthenia Gravis Foundation of America (MGFA), the largest average of myoid cells (26.7) was found in class III and being the histological type of True Hyperplasia (average 42.0). The myoid cells were identified in 11 thymus with Lymphoid Hyperplasia, in three with True Hyperplasias and in four with Normal thymus. The malignant thymoma (three) and a normal thymus did not present myoid cells. CONCLUSION: The myoid cells can be identified and quantified by the immunohistochemistry method with monoclonal antibody anti- desmin, however there is no correlation between the amount of myoid cells and demographic, clinics, pathological variables. They were not identified in spindle cells tymoma.
Myoid cells; Thymus; Immunohistochemical
