J. M. Verley

Two hundred thymomas, surgically treated between 1955 and 1982 at the Marie Lannelongue Surgical Center, were subjected to statistical analysis, comparing clinical stages and histologic types and relating them to survival. Clinical stages were defined as follows. Stage I: no invasiveness, total excision; Stage II: localized invasiveness (no more than two mediastinal structures); Stage III: largely invasive, with or without distant tumorous grafts, lymph node deposits, or metastases. Four histologic types were retained: (1) spindle or oval cell type thymoma, (2) lymphocyte-rich thymoma, (3) differentiated epithelial thymoma, and (4) undifferentiated epithelial thymoma. Invasiveness remained a major prognostic factor, but the degree of invasion did not affect the survival rate or always justify radical surgery. Thus, the survival rate dropped from 85% at 5 years and 80% at 10 years in noninvasive tumors to 50% and 35%, respectively, in invasive tumors, but without significant difference between moderately invasive Stage II and largely invasive Stage III tumors. Histologic typing indicated a good correlation between the degree of differentiation of the tumors and prognosis. The survival rates were 80% at 5 years and 75% at 10 years for spindle cell type 1 and lymphocyte-rich type 2 thymomas, 75% at 5 years and 50% at 10 years for differentiated epithelial type 3, and nil at 5 years for undifferentiated type 4 thymomas. Although invasiveness often paralleled histologic typing, they appeared as two distinct parameters with separate prognostic significance, particularly in differentiated and undifferentiated epithelial tumors. One hundred five patients had myasthenia gravis and 14 had another autoimmune disease. The associated syndromes were no longer an adverse factor in the prognosis of thymoma.

BACKGROUND: The records of 98 consecutive patients (58 males and 40 females; median age, 27 years; age range, 2-64 years) who presented with a primary germ cell tumor (GCT) of the mediastinum between January 1960 and December 1990 were reviewed. There were 45 mature teratomas, 8 immature teratomas, 16 pure seminomas, and 24 malignant nonseminomatous GCT (MNSGCT). RESULTS: All patients with mature teratomas were cured by radical resection alone, except one patient who died intraoperatively. Among the eight patients with immature teratomas, five were treated before the advent of cisplatin treatment (two children younger than 15 years were cured by surgery alone and three adults died within 7 months after operation). Three patients underwent surgery followed by cisplatin-based chemotherapy (two are still alive and one died of an associated rhabdomyosarcoma). Thirteen of 16 patients with seminomas (81%) were cured by surgery either alone (5 patients) or with adjuvant radiation therapy (8 patients). Among the 24 MNSGCT, 10 were treated before 1980 without cisplatin and all but 1 died of disease progression. Fourteen patients were treated by initial high-dose cisplatin combination chemotherapy and 8 (57%) achieved complete remission (2 died of systemic mastocytosis development). CONCLUSIONS: Results indicate the benignity of mature teratomas of the mediastinum, the age-dependent clinical course of immature teratomas, and the excellent prognosis of seminomas. The improved survival advantage resulting from cisplatin-based chemotherapy in MNSGCT is impaired by the propensity to nongerminal solid tumor development and hematologic malignancies.

17 thymomas were studied by indirect immunofluorescence for the presence of thymic hormones and antigens of the major histocompatibility complex (MHC). The thymoma epithelial cells (specifically identified by their keratin content) contained thymic hormones (thymulin and thymosin alpha 1), a finding corroborated by the observation of elevated thymulin serum levels. In contrast with normal or hyperplastic thymuses, thymoma epithelial cells did not express HLA-DR and HLA-DC antigens as assessed by immunofluorescence as well as immunoblot analyses. Conversely, MHC class I antigens (HLA-ABC) were normally expressed. Thus, we conclude that thymoma epithelial cells are endocrinologically active but are defective for the expression of some MHC products (class II molecules) known to play an essential role in intrathymic T cell differentiation.