Myasthenia gravis with thymoma: analysis of and postoperative prognosis for 65 patients with thymomatous myasthenia gravis

Germinal centers are associated with postthymectomy myasthenia gravis in patients with thymoma

BACKGROUND AND PURPOSE

Germinal centers (GCs) can be observed in the thymic tissues of patients with thymoma-associated myasthenia gravis (MG). Although an association between thymic GCs and MG has been suggested, it is unknown whether the presence of GCs could predict the development of MG after the resection of thymoma, known as postthymectomy MG.

METHODS

We conducted a retrospective analysis of previously nonmyasthenic patients who underwent surgical removal of the thymoma. All available thymic tissue slides were rereviewed by a pathologist to assess for GCs. Patients were classified into GC-positive and GC-negative groups based on the presence of GCs. The incidence of postthymectomy MG was compared between the two groups, and the risk factors for postthymectomy MG were assessed.

RESULTS

Of the 196 previously nonmyasthenic patients who underwent thymoma resection, 21 were GC-positive, whereas 175 were GC-negative. Postthymectomy MG developed in 11 (5.6%) patients and showed a higher incidence in the GC-positive group than in the GC-negative group (33.3% vs. 2.3%, p < 0.001). No postoperative radiotherapy and the presence of GCs were risk factors for postthymectomy MG in the univariate analysis. In multivariate analysis, invasive thymoma (hazard ratio [HR] = 9.835, 95% confidence interval [CI] = 1.358-105.372), postoperative radiotherapy (HR = 0.160, 95% CI = 0.029-0.893), and presence of GCs (HR = 15.834, 95% CI = 3.742-67.000) were significantly associated with postthymectomy MG.

CONCLUSIONS

Thymic GCs may be a significant risk factor for postthymectomy MG. Even in patients with thymoma who do not show clinical symptoms of MG, postthymectomy MG should be considered, especially if thymic GCs are observed.

[Clinical Study on the Prognosis of Patients with Thymoma with Myasthenia Gravis]

背景与目的

胸腺瘤常伴发重症肌无力（myasthenia gravis, MG），但是这些患者行胸腺切除的预后与MG的关系尚不明确。本研究旨在探讨影响胸腺瘤合并MG患者预后的因素。

方法

回顾性分析中国胸腺瘤协作组（Chinese Alliance for Research of Thymoma, ChART）数据库1992年-2012年875例随访20年资料完整的胸腺瘤病例，分析世界卫生组织（World Health Organization, WHO）组织学分型、Masaoka分期、术后辅助治疗与MG及预后的关系。

结果

胸腺瘤WHO组织学分型与MG有相关性，差异有统计学意义（χ²=24.908, P < 0.001）。MG发生率为22.7%，其中B2型（58/178, 32.58%） > B3型（65/239, 27.20%） > B1型（27/132, 20.45%） > AB型（43/267, 16.10%） > A型（6/59, 10.17%），Masaoka分期与MG无相关性（χ²=1.365, P=0.714）。生存分析表明WHO分型、Masaoka分期与预后有关（P < 0.05），而是否合并MG（χ²=0.113, P=0.736）、是否行胸腺扩大切除（χ²=1.548, P=0.213）、术后辅助放疗（χ²=0.380, P=0.538）与预后无相关，术后辅助化疗与差的预后相关（χ²=14.417, P < 0.001）。是否行胸腺扩大切除与MG的疗效有相关性（χ²=24.695, P < 0.001）。

结论

胸腺瘤患者是否合并MG和是否行胸腺扩大切除与预后无相关性，胸腺扩大切除可改善MG患者的疗效。

Thymoma: A Clinico-Pathologic Study Based on Newly Developed Morphologic Criteria

A retrospective study of 28 cases of thymoma classified according to Marino and Müller-Hermelink (cortical, medullary, mixed common, mixed with cortical predominance, mixed with medullary predominance thymoma) was undertaken to determine the existence of correlations between histology and clinical behavior. Cortical thymoma was observed in 11 cases (39.2%), mixed common thymoma in 9 (32.1%), mixed with cortical predominance in 5 (18%), and medullary thymoma in 3 (10.7%). In patients with cortical thymoma the tumor was always invasive (stages II and III according to Bergh), whereas medullary thymomas were noninvasive in 2 cases (stage I) and slightly invasive with a moderate infiltration of the capsule in the remaining case (stage II). Mixed common and mixed with cortical predominance thymomas displayed intermediate behavior. Twelve patients were affected by myasthenia gravis: 1 had medullary thymoma, 6 had mixed common thymoma, 3 had mixed thymoma with cortical predominance, and 2 had cortical thymoma. One patient with cortical thymoma had superior vena cava syndrome and 1 had erythroid hypoplasia; mixed common thymoma was associated with Cushing's syndrome in 1 patient. These data confirm previously reported observations (16) showing a higher degree of malignancy in patients with cortical thymoma.

Significance of B10 cell in patients with thymoma complicated with myasthenia gravis

A subset of regulatory B cells in humans has been identified as B10 cell which has the function of secreting interleukin-10. We evaluated the significance of B10 cell in patients with thymoma complicated with myasthenia gravis. In this study, 156 patients diagnosed with thymoma were enrolled, FCM was used to detected the percentage of Breg/CD19⁺B cells and CD19⁺B cells/PBMC, ELISA to evaluate the serum concentration of the relevant immunological markers; purified CD19⁺B cells in tissues by MACS; gene and protein expressions of CD19 and IL-10 by Real-time PCR and Western-Blot; double immunofluorescence staining to detect the distribution of CD19 and IL-10 in thymus tissues. Thymoma patients without MG mainly display the types A and AB of thymoma, whereas the thymoma patients with MG mainly display type B (B1, B2 and B3) thymoma; AChR-Ab in Tm + MG group was the highest, with the progress of the disease, the percentage of Breg/CD19⁺B cells increased and B10/CD19⁺B cells decreased (p < 0.05); ROC curve showed that B10 had the greatest significance for the clinical directivity of Tm+MG and cut-off point = 0.55%; in accordance with the Con, Tm and Tm+MG group, the content of CD19⁺IL-10⁺B10 cells increased gradually (p < 0.05); meanwhile, the gene and protein expression levels of CD19 and IL-10 gradually increased in the same way. It is concluded that with the progress of thymoma, the infiltration of Breg in tumour tissue increases; however, as the severity of MG increases, the function of Breg (B10 cell) in peripheral blood decreases and the cut-off point is 0.55%.

Myasthenia gravis and thymic neoplasms: A brief review

Thymoma is the most common mediastinal tumor. They have varied presentation ranging from asymptomatic incidental mediastinal masses to locally extensive tumor with compressive symptoms and distant metastases. They have frequent association with various paraneoplastic syndromes (PNS). The most common PNS associated with thymoma is myasthenia gravis (MG). Patients of thymoma with MG have a favourable outcome due to early disclosure of the disease. Histologically they are classified into five subtypes and Masaoka-Koga staging system is used for staging. Surgery, chemotherapy and radiotherapy play an important role along with anti-myasthenia drugs. This review would like to highlight the association of thymoma with MG and associated clinical and therapeutic issues.

Eight-year follow-up of patients with myasthenia gravis after thymectomy

PURPOSE

To depict the long-term outcome of patients with myasthenia gravis after thymectomy in combination with immunotherapy, and the factors that may potentially affect the outcome.

METHODS

The 306 patients with myasthenia gravis who underwent extended thymectomy from January 1984 to December 2011 at Tongji Hospital were retrospectively evaluated.

RESULTS

The patients consisted of 174 cases with thymoma and 132 cases without thymoma. Pharmaceutical treatment was tailored for each case during follow-up. Nine patients with thymomatous myasthenia gravis died during the perioperative period, and 297 patients were followed for 8.6 years. By their latest visits, 241 patients (81.1%) gained satisfactory efficacy, 24 cases died (8.1%), and 32 cases (10.8%) remained unchanged or deteriorated. Favorable factors for satisfactory efficacy included the presence of ocular myasthenia gravis before operation, no presence of thymoma, and lack of concomitant diseases. It is interesting to mention that, patients with non-thymomatous myasthenia gravis obtained significantly higher rates of complete stable remission and clinical remission than the patients with thymomatous myasthenia gravis.

CONCLUSIONS

Extended thymectomy combined with immunotherapy is a preferred treatment with a satisfactory long-term remission rate. Patients with non-thymomatous myasthenia gravis have a much more promising prognosis than the patients with thymomatous myasthenia gravis. However, appropriate caution must be taken to discontinue pharmaceutical therapy as relapse remains a major concern after a patient who has already undergone thymectomy becomes symptom-free.

Thymectomy for non-thymomatous myasthenia gravis

BACKGROUND

Treatments currently used for patients with myasthenia gravis (MG) include steroids, non-steroid immune suppressive agents, plasma exchange, intravenous immunoglobulin and thymectomy. Data from randomized controlled trials (RCTs) support the use of some of these therapeutic modalities and the evidence for non-surgical therapies are the subject of other Cochrane reviews. Significant uncertainty and variation persist in clinical practice regarding the potential role of thymectomy in the treatment of people with MG.

OBJECTIVES

To assess the efficacy and safety of thymectomy in the management of people with non-thymomatous MG.

SEARCH METHODS

On 31 March 2013, we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL (2013, Issue 3), MEDLINE (January 1966 to March 2013), EMBASE (January 1980 to March 2013) and LILACS (January 1992 to March 2013) for RCTs. Two authors (RS and GC) read all retrieved abstracts and reviewed the full texts of potentially relevant articles. These two authors checked references of all manuscripts identified in the review to identify additional articles that were of relevance and contacted experts in the field to identify additional published and unpublished data. Where necessary, authors were contacted for further information.

SELECTION CRITERIA

Randomized or quasi-randomized controlled trials of thymectomy against no treatment or any medical treatment, and thymectomy plus medical treatment against medical treatment alone, in people with non-thymomatous MG.We did not use measured outcomes as criteria for study selection.

DATA COLLECTION AND ANALYSIS

We planned that two authors would independently extract data onto a specially designed data extraction form and assess risk of bias; however, there were no included studies in the review. We would have identified any adverse effects of thymectomy from the included trials.

MAIN RESULTS

We did not identify any RCTs testing the efficacy of thymectomy in the treatment of MG. In the absence of data from RCTs, we were unable to do any further analysis.

AUTHORS' CONCLUSIONS

There is no randomized controlled trial literature that allows meaningful conclusions about the efficacy of thymectomy on MG. Data from several class III observational studies suggest that thymectomy could be beneficial in MG. An RCT is needed to elucidate if thymectomy is useful, and to what extent, in MG.

Prediction of thymoma histology and stage by radiographic criteria

Thymic epithelial tumors, such as thymomas and thymic carcinomas, are the most common primary neoplasms of the mediastinum. In 1999, the World Health Organization (WHO) proposed a consensus classification of thymic epithelial tumors based on the morphology of the epithelial cells and the ratio of lymphocytes to epithelial cells, which was revised in 2004. The latest classification system stratifies thymic epithelial tumors into six categories: types A, AB, B1, B2, B3, and thymic carcinoma. This article describes the prediction of thymoma histology and stage on the basis of radiographic criteria by reviewing the following: the WHO histologic classification of thymic epithelial tumors, the clinical staging of thymomas based on prognosis, and the radiographic appearance of thymomas according to the WHO histologic classification.

Prognosis of thymic epithelial tumors according to the new World Health Organization histologic classification

BACKGROUND

The aim of this study was to document the prognosis of thymic epithelial tumors (TETs) according to new the World Health Organization (WHO) classification.

METHODS

We retrospectively reviewed 150 patients with TETs that were confirmed pathologically during 11 years (from 1992 to 2002) in Severance Hospital, Seoul, Korea.

RESULTS

TETs were classified as type A, AB, B1, B2, B3, or C, tumors and these represented 7 (4.7%), 26 (17.3%), 13 (8.7%), 45 (30.0%), 26 (17.3%), and 33 (22.0%) cases, and the 5-year survival rates were 100%, 93%, 89%, 82%, 71%, and 23%, respectively. Their Masaoka stages were I, II, III, IVa, and IVb, with 53 (35.3%), 39 (26.0%), 20 (13.3%), 22 (14.7%), and 16 (10.7%) cases. Tumor invasiveness, recurrence, completeness of resection, and tumor-related death were more frequent in types AB, B2, B3, and C than in types A and B1. Multivariate analysis showed that Masaoka stage (p < 0.001) and the WHO classification (p = 0.019) were significant independent prognostic factors.

CONCLUSIONS

The WHO classification is associated with tumor invasiveness, recurrence, completeness of resection, and tumor-related death, and has good correlation with Masaoka stage. The WHO histologic subtypes are an independently significant prognostic factor with respect to survival in our multivariate analysis. Types AB, B2, B3, and C showed invasive behaviors and R1 or R2 resections were frequently performed. Postoperative adjuvant radiotherapy was effective, but long-term follow-up is recommended because of decreased survival after 5 years following operation. The WHO classification may be helpful in clinical practice for the assessment and treatment of TET patients.

Clinical and pathologic predictors of outcome in Thymoma-Associated myasthenia gravis

BACKGROUND

Myasthenia gravis is by far the most common paraneoplastic syndrome of thymomas. There is little information regarding the influence of clinical variables and thymoma-associated factors on biologic development of myasthenia gravis. The aim of the study was to determine independent predictors of clinical outcome in thymoma with myasthenia gravis.

METHODS

We studied 108 patients with thymoma-associated myasthenia gravis undergoing removal of the mediastinal mass between 1967 and 2000. Clinical and pathologic variables associated with clinical outcome of myasthenia were assessed by multivariate Cox regression analysis.

RESULTS

Patients were followed for a mean period of 10 years (9 months to 33 years). A total of 38 patients died (35.2%), in 14 cases (37%) because of myasthenia gravis and in 6 (16%) because of recurrence of thymoma. With respect to clinical outcome of myasthenia gravis, at the end of the follow-up period, the rate of remission was 16% (n = 17). Of the 91 patients in whom remission was not achieved, 55 had no symptoms with immunosuppressive medication and 36 had symptoms with medication.

CONCLUSIONS

In patients with thymoma-associated myasthenia gravis, well-differentiated thymic carcinoma (Müller-Hermelink system), age more than 55 years, and interval from the onset of symptoms to thymectomy of less than 1 year were found to be independent predictors of nonremission of myasthenia gravis after thymectomy.

[Predictors of survival in patients with myasthenia gravis and thymoma]

BACKGROUND AND OBJECTIVE

Myasthenia Gravis (MG) and Thymoma have different clinical evolutions and survival. There are few studies grying to describe the prognosis factors in patients with both thymoma and MG. We have evaluated all patients with thymoma and associated MG who were treated in our unit in order to identify possible predictors of survival.

PATIENTS AND METHOD

There were 108 patients with thymoma and associated MG treated at our center from 1967 to 2000. All data were analyzed by multivariate Cox regression analysis, which allowed quantification of the independent predictive value of prognostic indicators.

RESULTS

Median follow-up was 10 years. Mortality was 35.2% (38 patients). In 14 (36.8%) cases, death was related to MG, and 6 (15.8%) patients died from a cause directly related to thymoma. Cox regression analysis found a predictive value for both an age older than 55 years and the need for tracheostomy during the postoperative period.

CONCLUSIONS

In our series of patients with thymoma and associated MG, age older than 55 years and the need for postoperative tracheostomy were independent predictors of poorer overall survival.

Prognostic significance of thymomas in patients with myasthenia gravis

BACKGROUND

The presence of thymoma may be a negative prognostic factor with respect to the outcome of myasthenia gravis (MG).

METHODS

Of 122 consecutive patients with MG undergoing thymectomy between August 1994 and September 2000, 37 had a thymoma. Postoperative radiation was administered to all patients with stage II thymoma and higher. To determine differences in presentation and outcome, thymoma patients were compared with patients with atrophic (n = 49) or hyperplastic (n = 36) thymus gland on final pathology.

RESULTS

Thymoma patients were significantly older (52 +/- 14 vs 36 +/- 15 years, p < 0.0001) and included a significantly higher proportion of males (54% vs 28%, p = 0.006) than patients without thymoma. However, the preoperative Osserman grade and the duration of symptoms before surgery were not significantly different between groups. Mean follow-up after thymectomy was not significantly different between patients with or without thymoma (32 +/- 23 vs 37 +/- 19 months, respectively, p = 0.3). At last follow-up, the proportion of asymptomatic patients (63% vs 70%, respectively, p = 0.5) and the mean Osserman grade (0.6 +/- 0.9 vs 0.5 +/- 0.9, respectively, p = 0.6) were similar in both groups. In addition, the rate of complete remission reached 36% at 5 years in patients with or without thymoma (p = 0.8).

CONCLUSIONS

Although myasthenic patients with thymoma are significantly older and include a greater proportion of males, the overall outcome, including the rate of complete remission, was similar between patients with or without thymoma. Therefore, the presence of a thymoma should not necessarily be viewed as a negative prognostic factor regarding recovery from myasthenia gravis.

Transcervical thymectomy for myasthenia gravis achieves results comparable to thymectomy by sternotomy

BACKGROUND

It remains controversial whether transcervical thymectomy offers results equivalent to thymectomy by way of a median sternotomy in the treatment of myasthenia gravis. Furthermore, preoperative prognostic factors have not been clearly defined.

METHODS

This study is a retrospective chart review and interview of 78 patients completing transcervical thymectomy for myasthenia gravis between 1992 and 1999.

RESULTS

There were 24 men and 54 women. Mean age was 40 years (range, 13 to 78 years). Twelve patients were in Osserman class 1, 25 in class 2, 30 in class 3, and 11 in class 4 (mean, 2.5). There was no perioperative mortality and 6 (7.7%) morbidities. Mean length of stay was 1.5 days and mean follow-up, 54.6 months. The crude cumulative complete remission (asymptomatic off medications for 6 months) rate was 39.7% (n = 31). Only 8 patients (10.3%) failed to improve after transcervical thymectomy. Kaplan-Meier estimates of complete remission were 31% and 43% at 2 and 5 years, respectively. Eight patients with thymoma had a 5-year estimated complete remission rate of 75% in contrast to 43% in 38 patients with thymic hyperplasia and 36% in 32 patients with neither thymoma nor hyperplasia (p = 0.01). Twelve patients with ocular myasthenia had a 5-year estimated complete remission rate of 57%, whereas patients with mild-to-moderate (n = 55) or severe (n = 11) generalized symptoms had 5-year complete remission rates of 43% and 30%, respectively (p = 0.21).

CONCLUSIONS

Overall, extended transcervical thymectomy offers results that are comparable to those published for the transsternal procedure. Patients with milder disease (including isolated ocular disease) and taking no preoperative immunosuppressive agents appear to experience higher remission rates. In contrast to previous studies, we also find that small thymomas predict better responses to thymectomy.

Oncological significance of WHO histological thymoma classification. A clinical study based on 286 patients

OBJECTIVES

The clinical significance of thymoma histology remains controversial because of the numerous histological classifications of thymic epithelial tumors. Universal classification of such tumors was achieved by the World Health Organization (WHO) in 1999. We studied the prognostic significance of this classification.

METHODS

We studied clinical features and postoperative survival in cases of thymoma, but not thymic carcinoma, based on WHO histological classification in 286 patients undergoing surgery between 1958 and 2001.

RESULTS

Tumors were 19 type A, 79 type AB, 59 type B1, 102 type B2, and 27 type B3. The proportion of invasive tumors increased by type--from A to AB, B1, B2, and B3. The great vessels were involved more frequently in type B2 and B3 tumors than in type A, AB, and B1 tumors. The 20-year survival was 100% in type A, 87% in type AB, 91% in type B1, 65% in type B2, and 38% in type B3 tumors. Multivariate analysis showed Masaoka staging and WHO histological classification to be significant independent prognostic factors, while age, gender, myasthenia gravis association, resection completeness and great vessel involvement were not. In stage III patients, 13 of 45 patients with type B2 and B3 tumor died of their tumors, while no tumor deaths occurred in 11 patients with type A, AB, and B1 tumors.

CONCLUSION

WHO histological classification realistically reflects the oncological behavior of thymoma.

The World Health Organization histologic classification system reflects the oncologic behavior of thymoma: a clinical study of 273 patients

BACKGROUND

Although the histologic classification of thymic epithelial tumors has been confusing and controversial, an agreement on the universal classification system for thymic epithelial tumors was achieved by the World Health Organization (WHO) in 1999. The authors previously reported that the WHO histologic classification system reflects invasiveness and immunologic function of thymic epithelial tumors. In this subsequent study, they examined the prognostic significance of this classification system.

METHODS

Clinical features as well as postoperative survival of patients with thymoma, but not thymic carcinoma, were examined with reference to WHO histologic classification based on an experience with 273 patients over a 44-year period.

RESULTS

There were 18 type A tumors, 77 type AB tumors, 55 type B1 tumors, 97 type B2 tumors, and 26 type B3 tumors. In patients with type A, AB, B1, B2, and B3 tumors, the respective proportions of invasive tumor were 11.1%, 41.6%, 47.3%, 69.1%, and 84.6%; the respective proportions of tumors with involvement of the great vessels were 0%, 3.9%, 7.3%, 17.5%, and 19.2%; and the respective 20-year survival rates were 100%, 87%, 91%, 59%, and 36%. According to the Masaoka staging system, the 20-year survival rates were 89%, 91%, 49%, 0%, and 0% in patients with Stage I, II, III, IVa, and IVb disease, respectively. By multivariate analysis, the Masaoka staging system and the WHO histologic classification system were significant independent prognostic factors, whereas age, gender, association with myasthenia gravis, completeness of resection, or involvement of the great vessels were not significant independent prognostic factors.

CONCLUSIONS

This study showed that histologic appearance reflects the oncologic behavior of thymoma when the WHO classification system is adopted. The WHO classification system may be helpful in clinical practice for the assessment and treatment of patients with thymoma.

Timoma: discussão sobre tratamento e prognóstico

Objetivo: Mostrar uma casuística de pacientes com timoma, tratados cirurgicamente, com ou sem outra terapia associada, no Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Sudeste do Brasil, avaliando o prognóstico destes. Métodos: Entre 1965 e 1998 foram operados 104 pacientes com neoplasias do timo, sendo 69 (66,3%) do sexo masculino; a idade média ao diagnóstico foi de 47,9 ± 16,3 anos, com faixa de variação de 13 a 76 anos de idade. Resultados: Dos 104 operados, 89 (85,6%) foram submetidos a ressecção total do timoma, 6 (5,8%) a ressecção parcial e 9 (8,6%) a biópsia. O diagnóstico anatomopatológico (timoma x timoma maligno) e a cirurgia (biópsia x ressecção total x ressecção parcial) foram significativamente preditivos (p < 0,02) para o tempo médio de sobrevida. Conclusão: A ressecção completa é o tratamento de escolha para os timomas. Esses tumores, quando não invasivos e ressecados completamente, apresentam bom prognóstico imediato e tardio.

Myasthenia gravis with thymoma is more common in the Maori and Pacific Island populations in New Zealand

BACKGROUND

The association of myasthenia gravis (MG) with thymoma is well recognized. Our clinical impression has been that MG associated with thymoma may be more common in patients of Polynesian descent than in other races.

AIM

To determine the influence of ethnicity on the association of MG with thymoma in our population.

METHOD

Review of all cases of thymectomy performed at Greenlane Hospital in Auckland for the 20-year period from June 1978 to June 1998.

RESULTS

There were 103 thymectomies performed in the study period. Fifty-five thymomas were identified, 15 in subjects of Maori or Pacific Island ethnicity and 40 in subjects of other races, predominantly Caucasian. Ten of 15 Maori or Pacific Island subjects with thymoma had MG (67%), compared with 15 of 40 subjects of other races (37.5%, P = 0.05). The mean age of Maori or Pacific Island subjects with thymoma and MG was 42.5 years, compared with 56.3 years in subjects from other races (P = 0.06). All five Maori and Pacific Island subjects with invasive thymoma had MG, whereas only four of 15 subjects (27%) from other races with invasive tumours had MG (P < 0.01). The overall incidence of thymoma and the proportion of thymomas that were invasive did not differ between the ethnic groups.

CONCLUSIONS

Myasthenia gravis with thymoma occurs more frequently among Maori or Pacific Island people than in other racial groups in our population. This is due to an increase in the proportion of cases with thymoma who have MG in this group, while the overall frequency of cases of thymoma is similar between groups. MG with thymoma in the Maori or Pacific Island populations also presents at a younger age and is more often associated with tumour invasion.

T lymphocyte activation in myasthenic thymoma

The functional and phenotypic characteristics of lymphocytes separated from myasthenic thymoma (Th-L) were compared with those of lymphocytes separated from non-thymomatous thymus associated with thymoma (NTh-L) of the same patients and NTh-L of myasthenia gravis (MG) patients without thymoma. We examined whether Th-L and NTh-L of MG patients reacted to interleukin-2 (IL-2) to develop lymphokine-activated killer (LAK) activity and/or cytolytic activity against K562 (natural killer (NK) activity), and the phenotypic changes in such cells during incubation. Ten MG patients with thymoma and six MG patients without thymoma, and four non-MG thymoma patients were included in this study. Th-L and NTh-L of MG patients reacted with IL-2 to develop LAK and NK activities. The LAK activity developed from Th-L was significantly higher than that from NTh-L, and the LAK activity developed from Th-L was as high as that from peripheral blood lymphocytes (PBL) in MG patients without thymoma. The proportions of CD3+ cells, CD4+/CD8- cells, and CD4-/CD8+ cells in Th-L of MG patients increased significantly during incubation. On the other hand, the proportion of CD4+/CD8+ cells in Th-L of MG patients decreased significantly. The proportions of CD4+/CD8- cells, CD4-/CD8+ cells, and CD4+/CD8+ cells in NTh-L of MG patients with and without thymoma exhibited no change during incubation. These findings suggest that CD4+/CD8+ Th-L of MG patients may have a higher potential to react to IL-2 than NTh-L, and that the former cells might develop LAK activity like that of PBL on maturation to CD4+/CD8- cells and CD4-/CD8+ cells. Our findings also suggested that Th-L might play an important role in the pathogenesis of MG with thymoma.

Myasthenia gravis

Adult-onset myasthenia gravis is an acquired autoimmune disorder of neuromuscular transmission in which acetylcholine receptor antibodies attack the postsynaptic membrane of the neuromuscular junction. Although the cause of this disease is unknown, the role of immune responses in its pathogenesis is well established. Circulating acetylcholine receptor antibodies are present in 80% to 90% of patients with the generalized form of myasthenia gravis. Most patients have ptosis, diplopia, dysarthria and dysphagia. The weakness and fatigue worsen on exertion and improve with rest. Respiratory muscle and limb weakness are rare at the onset of the disease. For the past two decades, there has been considerable progress in understanding the diagnosis and management of myasthenia gravis. The diagnosis is based on clinical presentation, neurologic examination, and confirmation by means of electrophysiologic testing and immunologic studies. Myasthenia gravis mimics many neuromuscular diseases and even illnesses such as depression and chronic fatigue syndrome. One should always exclude drug-induced myasthenia gravis for all patients. With the introduction of new modalities of treatment, particularly immunosuppressive or immunomodulating drugs, plasma exchange and thymectomy, the morbidity and mortality of myasthenia gravis have decreased dramatically to the point that myasthenia gravis should not be considered as serious a disease as it once was. Although the several therapeutic options are usually effective and have meant independence in daily life to many patients with myasthenia gravis, well-designed, controlled, prospective studies are still lacking.

Extended thymectomy for myasthenia gravis patients: a 20-year review

BACKGROUND

Since 1973 we have performed extended thymectomy for myasthenia gravis because of the presence of thymic tissue in the anterior mediastinal fatty tissue. Follow-up results were reviewed and influencing factors were investigated.

METHODS

Three hundred seventy-five patients with myasthenia gravis (286 nonthymomatous and 89 thymomatous) who have undergone extended thymectomies were reviewed. The status of the patients was evaluated as follows: A (remission), B (improvement), C (no change), D (deterioration), E (death due to myasthenia gravis). Evaluation was performed at 3 and 6 months, and at 1, 3, 5, 10, 15, and 20 years. The effectiveness of the operation was estimated by the remission rate (RR = A/Total number of patients evaluated) and the palliation rate (PR = A + B/Total number of patients evaluated) at each point.

RESULTS

Remission rates of the nonthymomatous patients were 15.2% (3 months), 15.9% (6 months), 22.4% (1 year), 36.9% (3 years), 45.8% (5 years), 55.7% (10 years), 67.2% (15 years), and 50.0% (20 years). Remission rates in the thymomatous patients were 13.6% (3 months), 17.5% (6 months), 27.5% (1 year), 32.4% (3 years), 23.0% (5 years), 30.0% (10 years), 31.8% (15 years), and 37.5% (20 years). Absence of thymoma, younger age, and short duration of the disease were favorable prognostic factors. Thymectomy was effective also in patients with ocular myasthenia gravis. Preoperative steroid administration did not improve the outcome.

CONCLUSIONS

Extended thymectomy is an excellent operative procedure for myasthenia gravis in both nonthymomatous and thymomatous patients.

Myasthenia gravis induces the activation and maturation of lymphocytes in thymoma

The biological differences between lymphocytes separated from thymoma patients with myasthenia gravis (MG) and those separated from thymoma patients without MG was examined. We investigated whether lymphocytes in thymoma (Th-L) of patients with and without MG could react to interleukin-2 (IL-2) to develop cytolytic activity against K562 and lympho kine-activated killer (LAK) activity, and their phenotypic changes during incubation with IL-2. Sixteen thymoma patients who consisted of eight patients with MG and eight patients without MG were investigated. Th-L of all MG patients could react to IL-2 to develop LAK activity. Th-L of all of MG patients also developed cytolytic activity against K562 target cells. Cytolytic activity against K562 and LAK activity from Th-L of the MG patients were significantly higher than those from Th-L of the patients without MG (P < 0.01, P < 0.01). The proportions of CD3+ and CD4-/CD8+ cells of Th-L of MG patients increased significantly during the incubation period with IL-2 (P < 0.05, P < 0.05). The proportion of CD4+/CD8+ cells of Th-L of patients with MG decreased significantly (P < 0.05) during incubation with IL-2. On the other hand, there was no significant phenotypic change in Th-L of the patients without MG. These results indicate that MG induces the functional and phenotypic activation and functional and phenotypic maturation of Th-L.

Neuromuscular disorders in systemic malignancy and its treatment

Neuromuscular dysfunction in patients with known or suspected malignancy has three basic etiologies: (1) a direct effect of the neoplasm, either by compression or infiltration; (2) a "remote," or paraneoplastic, effect of cancer; or (3) a side effect of anticancer treatment, radiation or chemotherapy. A variety of clinical features or syndromes are due to damage either at the level of the neuron (anterior horn cell or dorsal root ganglion neuron), nerve root(s), brachial or lumbosacral plexus, peripheral nerve (motor, sensory, and/or autonomic), neuromuscular junction, or muscle. A complex clinical picture evolves when dysfunction in due to more than one cause at more than one anatomical site.

Thymus cells in myasthenia gravis: a two-colour flow cytometric analysis of lymphocytes in the thymus and thymoma

The thymus in patients with myasthenia gravis has germinal centres and the thymic lymphocytes spontaneously produce anti-acetylcholine receptor antibody in vitro. This suggests indirectly that the myasthenic thymus contains mature T and B cells that are autoreactive. We report a two colour flow cytometric analysis of the surface antigen phenotype of lymphocytes in the thymus and in thymoma in 24 patients and in 14 normal thymuses. The results show a decline in the proportion of double positive immature thymocytes with age. This process seems to be partially disrupted in patients with myasthenia gravis. In addition titres of anti-acetylcholine receptor antibody were positively correlated with the proportion of mature single positive T cells and non-T DR positive cells.

Lymphocytes in thymomas are tolerant to self-MHC

Neoplastic epithelial cells of thymoma apparently retain the function of the cortical epithelial cells of normal thymus because a large number of nonneoplastic T cells in thymomas are often CD4+8+. However, the lack of medullary structure suggests that thymomas may lack some of the function of the normal thymus, especially the function of the medullary interdigitating cells to induce tolerance to self-antigens on T cells. Thymoma is often associated with autoimmune diseases, most frequently, myasthenia gravis. This suggests that the microenvironment of a thymoma may not be able to induce T cell tolerance to self-antigens. We addressed this question by testing the lymphocytes in thymomas for proliferative responses to mitogens and allogeneic or autologous stimulator cells. The lymphocytes in thymomas proliferated consistently in response to PHA and to allogeneic cells even when the response to OKT3 was undetectable. However, neither the thymoma lymphocytes nor the peripheral blood lymphocytes in these patients proliferated in response to autologous cells.

Chemotherapy for invasive thymoma. A 13-year experience

From 1977 to 1990, 37 patients with Stage III or IV invasive thymoma (20 men and 17 women; median age, 40 years of age) were referred for chemotherapy to the Padova Medical Oncology Department. All patients initially received the same regimen (50 mg/m2 of cisplatin and 40 mg/m2 of doxorubicin intravenously (IV) on day 1, 0.6 mg/m2 of vincristine IV on day 3, and 700 mg/m2 of cyclophosphamide IV on day 4 [ADOC]), recycling at monthly intervals. No life-threatening side effects were noted. The overall clinical response rate (complete response plus partial response) was 91.8%, with 43% complete remissions. Median duration of response and survival were 12 months (range, 2 to 96+ months) and 15 months (range, 5 to 96+ months), respectively. Seven of the 16 complete remissions were pathologically confirmed at subsequent thoracotomy. Other chemotherapy combinations and radiation therapy have been applied as second-line treatment, achieving only minimal responses. In the opinion of the authors, such chemotherapy deserves evaluation for adjuvant and neo-adjuvant treatment of invasive (and/or inoperable) thymoma due to the high complete response rate and overall response rate.

Circulating CD4+CD8+ cells in myasthenia gravis: supplementary immunological parameter for long-term prognosis

Twenty patients with myasthenia gravis (MG) were studied prospectively for up to 5 years after thymectomy, in order to clarify the relationships between disease severity, anti-acetylcholine receptor antibody (anti-AChR) titres, proportions of circulating CD4+CD8+ cells (CD4+CD8+ cell level) and major lymphocyte subsets. The CD4+CD8+ cell levels were closely related to the clinical change within 1 year after surgery in 8 patients who showed a preoperative elevation in the cell levels. This group of patients consisted of six thymomatous and two non-thymomatous patients; the latter were both negative for anti-AChR. The anti-AChR titres generally changed in parallel with the clinical state in 9 of the 16 patients who were followed up for more than a year after thymectomy, and the CD4+CD8+ cell levels were useful in predicting the clinical course in 6 of the above 9 patients and 3 other patients, including antibody-negative cases. The present study suggests that the CD4+CD8+ cell levels may serve as an indicator for long-term prognosis of MG.

The characteristics of thymoma with myasthenia gravis: a 28-year experience

Of 134 patients with thymoma, 79 (59%) also had myasthenia gravis (MG). The thymoma with MG differed from that in the absence of MG in the following aspects: The ratio of lymphocytes to epithelial cells in the tumor was larger, the polygonal cell type was more prominent (i.e., in 83% of the MG patients this cell type predominated), and the differentiation of epithelial cells in the tumor was more advanced in the group with MG than in the group without MG. Furthermore, the clinical stage of thymoma was earlier, the recurrence rate was lower, and the survival curve was better in the group with MG than in the group without MG. These findings suggest that the thymoma with MG is less malignant than that without MG.

Thymectomy in the treatment of myasthenia gravis: report of 247 patients

We made a retrospective assessment of the long-term outcome in 247 consecutive patients with myasthenia gravis (MG) who underwent thymectomy in the period January 1971-December 1985. In 84 cases a thymoma was found at surgery, while 163 patients had a non-neoplastic thymus. The duration of symptoms before surgery, the age at onset of the disease and the presence of germinal centres in the thymus did not appear to influence the prognosis. Patients with a non-neoplastic thymus showed a better response to thymectomy. Thymoma was associated with more severe disease and with a higher mortality; moreover, more thymoma patients required corticosteroid treatment in order to achieve good therapeutic results. In our opinion, thymectomy is indicated in the treatment of generalized MG, while ocular myasthenia seems not to be improved by the removal of the thymus.

Neuromuscular disorders and thymoma

We describe a patient who had asymmetrical atrophy of limb muscles and myasthenic weakness of neck, facial, and bulbar muscles. Electrophysiological tests indicated myasthenia gravis of facial muscles and changes consistent with an asymmetrical motor neuropathy as a cause of the muscle atrophy. Both conditions occurred as complications of a locally invasive thymoma, and both failed to improve after surgery and radiation but substantially improved with subsequent treatment by corticosteroids, azathioprine, and plasmapheresis. Review of the literature disclosed that several neuromuscular conditions may be associated with thymoma, the commonest being myasthenia gravis. Muscle atrophy may occur in 10% of patients who have myasthenia gravis, whether associated with or without thymoma. Its mechanism is debated, and further studies are needed, but observations in our patient suggest the atrophy is due to a motor neuropathy. Primary treatment of the thymoma by surgery, irradiation if the tumor is invasive, and immunosuppressive therapy for neuromuscular complications offers a relatively good prognosis for this group of patients.

Thymus in myasthenia gravis. Isolation of T-lymphocyte lines specific for the nicotinic acetylcholine receptor from thymuses of myasthenic patients

The thymus is believed to play a central role in the pathogenesis of Myasthenia gravis (MG). According to a previous hypothesis, MG is initiated within the thymus by immunogenic presentation of locally produced nicotinic acetylcholine receptor (AChR) to potentially autoimmune T cells. Data of 10 consecutive MG patients demonstrate two critical features of MG thymuses that support the concept of intrathymic activation of autoreactive, AChR-specific lymphocytes. Morphologically, the thymuses showed lympho-follicular hyperplasia in nine cases and benign thymoma in one case. The paramount feature revealed by immunohistological double marker analyses was the intimate association of myoid cells (antigen producing) with interdigitating reticulum cells (potentially antigen presenting cells), both of which were surrounded by T3+ lymphocytes in thymus medulla. All 10 thymuses contained T lymphocytes reactive with AChR. This was in contrast to the peripheral immune compartment (blood) where in only 3 of 10 patients, significant T cell responses to AChR were observed. AChR-specific T cell lines could be established from 8 of 10 thymuses, all members of the helper/inducer subset as indicated by the expression of markers T3 and T4.

Thymoma. The most common anterior mediastinal mass

Thymomas may be discovered during routine evaluation, through reported symptoms, or increasingly, during evaluation for myasthenia gravis. Histologic details of these tumors have little bearing on prognosis or evaluation of malignant potential. Malignancy is determined by evidence of invasion through the tumor capsule at surgery or of distant spread. Complete surgical excision is the mainstay of therapy for both benign and malignant thymoma. Biopsy of anterior mediastinal masses via mediastinoscopy should be avoided because of the risk of violating the thymoma capsule. If the capsule is surgically violated or extracapsular invasion is present, postoperative radiation therapy is indicated.

Clinical characteristics and prognosis of myasthenia gravis with other autoimmune diseases

Of 277 patients with myasthenia gravis (MG) who underwent thymectomy, including 78 with thymomatous MG, 33 patients had other autoimmune diseases. The clinical characteristics of MG with other autoimmune disease were investigated. Graves's disease and rheumatoid arthritis were the most common autoimmune diseases seen. The association rate of autoimmune disease in patients with thymomatous MG (3.8%) was significantly lower than that in patients with nonthymomatous MG (15.1%). The positive rate for a germinal center in the thymus was significantly higher in patients with other autoimmune disease than in those without such disease. Thymectomy was effective for MG in patients with an associated disease as well as in those without such a complication. The clinical course of the associated autoimmune disease did not seem to be adversely affected by thymectomy. Therefore, thymectomy should be performed in MG patients with other autoimmune disease.

Thymectomy for myasthenia gravis: 14-year experience

Forty-eight consecutive patients with myasthenia gravis (MG) attended by generalized weakness were treated by complete thymectomy, performed transsternally in 46 patients and through a left thoracotomy in two with thymomas. There were no operative deaths. A 12-year-old child with fulminating MG died of acute pneumonia shortly after hospital discharge. Of the remaining 47 evaluable patients, thymectomy resulted in complete remission in six, marked improvement with a reduced need for medication in 20, and mild improvement on the same dosage of medication in 18. Neither the age of the patient, nor the histopathology of the excised thymus, nor the postoperative change in acetylcholine receptor antibody titer were found to have a significant influence on the response to thymectomy. If the ten patients who were 20 years of age or younger were excluded, the patients with a shorter duration of MG achieved a better response to operation. The authors conclude that thymectomy is effective treatment for MG, regardless of the age of the patient or the type of thymic pathology.

Myasthenia gravis in elderly patients

The clinical features and the effect of thymectomy were compared between 27 elderly patients (Group 2) and 119 young adult patients (Group 1) with myasthenia gravis (MG). In the elderly group, MG was type I in 3 patients, type IIA in 6, type IIB in 17, and type III in 1; and in the young group, type I in 6, type IIA in 36, type IIB in 73, and type III in 4. The association rate with autoimmune disease in patients without thymoma was 12.5% (1/8) in Group 2 and 21.3% (20/94) in Group 1. Autoimmune diseases were not seen in any patients with thymoma. The clinical stage of thymoma was not significantly different between the two groups. The rates of remission and of palliation at 3 years after thymectomy were 18.2% and 72.7%, respectively, in Group 2 patients with thymoma, 21.4% and 78.6% in Group 1 patients with thymoma, 50% and 100% in Group 2 patients without thymoma, and 50% and 98.1% in Group 1 patients without thymoma.