Long-term survival and prognostic factors in thymic epithelial tumours☆

WHO types A and AB thymomas: not always benign

The 2004 WHO classification of thymic tumors recognizes five major subtypes of thymomas and thymic carcinoma. Subtypes A and AB thymomas are purported to be benign neoplasms, although prior studies have suggested a potential for malignant behavior. The purpose of this study was to assess the clinical behavior of A and AB thymomas identified from a large institutional pathologic database. A retrospective slide review of 500 thymic epithelial tumors identified 71 (∼ 14%) cases of types A and AB thymomas. Clinical history and follow-up information were obtained through retrospective chart review. There were 38 and 33 cases of types A and AB thymomas, respectively. Complete follow-up data were available in 37 (52%) cases. Eighteen (49%) patients (type A, n=9 and type AB, n=9) had evidence of recurrent/metastatic disease at an average of 62 months (range from 6 to 244 months) after initial diagnosis. Survival curves for patients with types A and AB thymomas, with and without recurrences, show a statistically significant difference (P=0.001 and 0.005, respectively). Analysis of this large cohort confirms the potential for subtypes A and AB thymomas to show malignant behavior. Long-term clinical monitoring, therefore, appears to be justified in these cases. This study also shows the poor correlation between the WHO classification and tumor behavior.

Thirty-five-year follow-up analysis of clinical and pathologic outcomes of thymoma surgery

BACKGROUND

The impact of myasthenia gravis on patients with thymoma is still controversial when perioperative and long-term outcomes are analyzed. With the unique opportunity of a 35-year follow-up in a single institution, thymomatous myasthenia gravis cohort, we investigated the influence of early and long-term clinical predictors.

METHODS

We reviewed a surgical series of 317 (1972 to 2007) patients with thymoma: clinical and pathologic features were analyzed as prognostic factors matched against the short- and long-term survival and recurrence rates.

RESULTS

Male to female ratio was 153:164; median age, 49 years. Myasthenia gravis coexisted in 276 patients (87.1%). Thymomas were classified according to the Masaoka (42.0% stage I, 32.2% stage II, 21.5% stage III, and 4.4% stage IV) and the World Health Organization (3.5% type A, 9.5% type AB, 19.2% type B1, 57.7% type B2, 8.2% type B3, and 1.9% thymic carcinoma) staging systems. The resection was complete in 295 patients (93.1%). Operative mortality and morbidity were respectively 1.6% and 7.6%. No differences were recorded in postoperative outcome stratifying for myasthenia gravis or comorbidities. Mean follow-up was 144.7 +/- 104.4 months. The overall 5-, 10-, 20-, and 30-year survival rates were 89.9%, 84.1%, 73%, and 58.6%, respectively. The completeness of resection (p < 0.001), the Masaoka staging (p = 0.010), and the World Health Organization classification (p < 0.001) all significantly influenced the long-term survival (univariate analysis). Only completeness of resection was significantly correlated with a better prognosis (p < 0.001) in multivariate analysis. Masaoka staging (p < 0.001) and World Health Organization classification (p < 0.001) significantly correlated with the disease-free survival in the univariate and multivariate analyses as significant prognostic factors (Masaoka, p < 0.001; World Health Organization, p = 0.011). Myasthenia gravis patients showed a better prognosis in terms of long-term survival (p = 0.046) and disease-free survival (p = 0.012) in the univariate analysis.

CONCLUSIONS

We confirm the evidence that the clinical staging and the histologic classification influence long-term survival. The presence of myasthenia gravis was not significantly related to operative outcome, but prolongs both long-term survival and disease-free survival.

The role of a pseudocapsula in thymic epithelial tumors: outcome and correlation with established prognostic parameters. Results of a 20-year single centre retrospective analysis

BACKGROUND

Treatment of thymoma is often based on observation of only a few patients. Surgical resection is considered to be the most important step. Role of a pseudocapsula for surgery, its clinical significance and outcome compared with established prognostic parameters is discussed which has not been reported so far.

METHODS

84 patients with thymoma underwent resection and analysis was carried out for clinical features, prognostic factors and long-term survival.

RESULTS

Fifteen patients were classified in WHO subgroup A, 21 in AB, 29 in B and 19 patients in C. Forty two patients were classified in Masaoka stage I, 19 stage II, 9 stage III and 14 stage IV. Encapsulated thymoma was seen in 40, incomplete or missing capsula in 44 patients. In 71 complete resections, local recurrence was 5%. 5-year survival was 88.1%. Thymomas with pseudocapsula showed a significant better survival (94.9% vs. 61.1%, respectively) (p = 0.001) and was correlated with the absence of nodal or distant metastasis (p = 0.04 and 0.001, respectively). Presence of pseudocapsula as well as the Masaoka and WHO classification, and R-status were of prognostic significance. R-status and Masaoka stage appeared to be of independent prognostic significance in multivariate analysis.

CONCLUSION

Intraoperative presence of an encapsulated tumor is a good technical marker for the surgeon to evaluate resectability and estimate prognosis. Although the presence of a capsula is of strong significance in the univariate analysis, it failed in the multivariate analysis due to its correlation with clinical Masaoka stage. Masaoka stage has a stronger relevance than WHO classification to determinate long-term outcome.

Thymomas: review of current clinical practice

Thymomas are the most common tumors of the mediastinum. The introduction of multimodality treatment strategies, as well as novel approaches to the diagnosis of these tumors, has led to changes in the clinical management of thymomas. Here we review the literature for current clinical practice in the diagnosis, management, and treatment of thymomas.

Evidence-Based Pathology and the Pathologic Evaluation of Thymomas: Transcapsular Invasion Is Not a Significant Prognostic Feature

Context.—Evaluation of transcapsular invasion is currently considered very important in the pathologic examination of thymomas. However, recent studies have questioned the prognostic value of stratifying thymoma patients into stage I and II disease. Evidence-based pathology promotes the use of systematic reviews of literature and meta-analysis of data to synthesize the results of multiple publications.

Objective.—To analyze the data in the literature regarding the prognostic importance of transcapsular invasion in thymoma stage I and II.

Design.—A systematic review of the English literature was carried out for “thymoma,” “stage,” and “prognoses.” Case reports, case series with fewer than 10 cases, and studies with follow-up periods shorter than 5 years were excluded. Twenty-one retrospective publications reporting the experience with 2451 thymomas were selected for review, including 1419 stage I and 1032 stage II patients. Meta-analysis was performed, and possible publication bias was studied with funnel plots of precision and various statistics.

Results.—Meta-analysis yielded no significant differences in disease-free or overall survival rates in stage I and II thymoma patients. Funnel plots of precision and statistical tests such as the Egger regression intercept test showed no significant publication bias.

Conclusions.—The lack of significant differences in the prognosis of patients with stages I and II thymoma suggests that evaluation of transcapsular invasion is of no clinical value in tumors that lack invasion of neighboring organs or the pleura. The data regarding the prognosis of stage II thymoma patients is somewhat heterogenous, with only some individuals having been treated with radiation therapy, suggesting the need for future randomized controlled trials.

Optimal therapy for thymoma

Thymoma is the most common tumor of the anterior mediastinum. This tumor is associated with unique paraneoplastic syndromes (myasthenia gravis, pure red cell aplasia, hypogammaglobulinemia, and other autoimmune diseases). The rarity of this tumor has somewhat obscured the optimal treatment. Although the histologic classification of thymoma has remained a subject of controversy for many years, the WHO classification system, published in 1999, appeared to be an advance in our understanding of thymoma. The optimal treatment for thymoma depends on its clinical stage. Surgery remains the mainstay of treatment for thymic epithelial tumors. Thymomas also have a high response rate to chemotherapy or radiotherapy. Only surgical resection is performed for patients with stage I (non-invasive) thymoma. The value of postoperative radiotherapy in completely resected stage II or III tumors is questionable. Multimodality therapy involving surgery, chemotherapy and radiotherapy appears to increase the rate of complete resection and survival in advanced (stage III and IV) thymomas.

Thymic epithelial tumours: a population-based study of the incidence, diagnostic procedures and therapy

The population-based incidence, diagnostic procedures, therapy and survival of thymic epithelial tumours were determined using the Netherlands National Pathological Archives and the Netherlands Cancer Registry. Excess mortality compared to the Netherlands standard population was estimated by relative survival analysis. Between 1994 and 2003, 537 thymic epithelial tumours were diagnosed. The incidence of all thymic epithelial tumours was 3.2/1,000,000. Diagnosis was obtained by primary resection in 56% of cases. Survival data were available for 232 cases. Not only thymic carcinomas (type C) but also thymomas (types B1-B3) were associated with excess mortality. Cases that underwent resection (78%) had a better survival than non-operated cases (median survival >10 years versus 1.1 years, p<0.001). Amongst the surgically treated cases (n=180), the completeness of resection did not predict survival (p=0.53). Thymic epithelial tumours are rare. Excess mortality was observed in the majority of tumours. Surgery offers the best perspectives, even if the resection is incomplete.

Novel prognostic groups in thymic epithelial tumors: assessment of risk and therapeutic strategy selection

PURPOSE

To assess the role of multimodality treatment on patients with thymic epithelial tumors (TETs) (i.e., thymomas and thymic squamous cell carcinoma) and to define the prognostic classes according to the Masaoka and World Health Organization histologic classification systems.

METHODS AND MATERIALS

Primary surgery was the mainstay of therapy. Extended thymectomy was performed in all cases. The cases were primarily staged according to the Masaoka system. Adjuvant radiotherapy was given to patients diagnosed with Masaoka Stage II, III, and IVA TET. Adjuvant chemotherapy was administered in selected cases.

RESULTS

We reviewed the records of 120 patients with TETs, with a mean follow-up of 13.8 years. Of the 120 patients, 98 (81.6%) received adjuvant radiotherapy. Of these 98 patients, Grade 1-2 pulmonary or esophageal toxicity was acute in 12 (12.2%) and late in 8 (8.2%). The median overall survival was 21.6 years. Of the 120 patients, 106 were rediagnosed and reclassified according to the World Health Organization system, and the survival rate was correlated with it. Three different prognostic classes were defined: favorable, Masaoka Stage I and histologic grade A, AB, B1, B2 or Masaoka Stage II and histologic grade A, AB, B1; unfavorable, Stage IV disease or histologic grade C or Stage III and histologic grade B3; intermediate, all other combinations. The 10- and 20-year survival rate was 95% and 81% for the favorable group, 90% and 65% for the intermediate group, and 50% and 0% for the unfavorable group, respectively. Local recurrence, distant recurrence, and tumor-related deaths were also evaluated.

CONCLUSION

The analysis of our experience singled out three novel prognostic classes and the assessment of risk identified treatment selection criteria.

Primary intrapulmonary thymoma: A systematic review

AIM

This article reviews the literature on the clinical features, diagnosis and management of primary intrapulmonary thymoma.

METHODS

Medline, Embase and Cochrane Library searches were performed on all relevant Anglo-Saxon language articles. The search words included "primary pulmonary thymoma" and "intrapulmonary thymoma". Secondary references were obtained from key articles. Prognostic and treatment strategies were analyzed by the Kaplan-Meier method, comparisons between curves were made using log rank test.

RESULTS

The searches yielded 25 cases of primary intrapulmonary thymoma. Median follow-up was 9 months (1 day to 13 years). At follow-up, 14 patients were tumor free, one patient had a local recurrence 8 years after radiotherapy, one patient responded favorably to radiotherapy, six patients died and three patients were lost to follow-up. The presence of a paraneoplastic syndrome decreased survival (P=0.02), however, histological subgroup (P=0.216), clinical stage (P=0.63) and tumor size (P=0.288) did not affect survival. Survival in surgically managed patients was significantly better than in conservatively managed patients (P=0.039). Adjuvant radiotherapy did not provide any benefit (P=0.4).

CONCLUSION

Complete resection of primary intrapulmonary thymomas appears sufficient in non-malignant tumors. Because of the risk of late local recurrence, long-term regular clinical follow-up is warranted.

Clinical value of the WHO classification system of thymoma

Since the World Health Organization (WHO) histologic classification system for thymoma was introduced in 1999, several centers have published results using this system. This review of the published experience with the WHO system examines whether the classification is reproducible, whether the WHO system defines clinically distinct patient groups, assesses the independent prognostic value of the WHO type by multivariate analysis, and discusses the impact of the WHO system on clinical management decisions.

Thymomas: a cytological and immunohistochemical study, with emphasis on lymphoid and neuroendocrine markers

Background

The current study correlates cytologic morphology with histologic type and describes immunophenotypes with a focus on epithelial, neuroendocrine, and lymphoid characteristics in an institutional series of surgically excised thymomas.

Methods

Fine needle aspirates (FNAs) and surgical specimens were retrospectively analyzed, and immunohistochemical stains were performed for EMA, cytokeratin 7, cytokeratin 20, CD57 CD5, bcl-2, calretinin, vimentin, CD3, CD20, CD1a, CD99 and Ki67. Tumors were classified by WHO criteria.

Results

There were eleven male and six female patients with an age range of 41 to 84 years (mean, 61 years) and a male to female ratio of 1.8:1. Four thymomas (4/17, 23.5%) were associated with neuromuscular disease: myasthenia gravis (n = 3) and limbic encephalitis (n = 1). FNA, under CT guidance, was performed in 7 cases. The positive predictive value for thymoma by FNA cytology was 100% and the sensitivity was 71%. Thymomas associated with neuromuscular disorders were WHO types B2 (n = 1) and B3 (n = 3), and showed a strong expression of CD57 in the majority of neoplastic epithelial cells accompanied by large numbers of CD20+ intratumoral B lymphocytes. Two of seventeen (11.7%) thymomas (all sporadic B3 type) contained numerous neoplastic epithelial cells positive for CD5 and bcl-2.

Conclusion

Our results suggest that thymomas associated with autoimmune disorders contain a significant population of CD20+ intratumoral B lymphocytes. Strong CD57 positivity in thymomas may suggest a concomitant neuromuscular disorder, notably myasthenia gravis. CD5 expression is of limited value in the differential diagnosis of primary thymic epithelial neoplasms since both thymic carcinomas and thymomas may express CD5.

Multidisciplinary Treatment for Advanced Invasive Thymoma with Cisplatin, Doxorubicin, and Methylprednisolone

BACKGROUND AND OBJECTIVES

Advanced invasive thymomas are not usually manageable by surgical resection and radiotherapy. We reviewed our experience with a multidisciplinary approach and evaluated chemotherapy in the treatment of invasive thymoma.

PATIENTS AND METHODS

Seventeen consecutive patients with invasive thymoma were treated with multimodality therapy consisting of chemotherapy, surgery, and/or radiotherapy. Four patients had stage III disease with superior vena cava invasion, nine had stage IVa disease, and four had stage IVb disease. The chemotherapy regimen consisted of cisplatin, doxorubicin, and methylprednisolone (CAMP). Chemotherapy was administered in a neoadjuvant setting to the 14 patients and in an adjuvant setting to the remaining three patients. Surgical resection was intended in all patients. After those treatments, chemotherapy and/or radiation therapy were performed.

RESULTS

All but one of the 14 patients with induction chemotherapy responded to the CAMP therapy, and the response rate was 92.9%. Seven of these patients underwent complete remission after surgical resection and chemoradiotherapy, and the others underwent partial remission. All three patients treated with surgical resection and then chemotherapy with or without radiotherapy also achieved complete remission. Tumor progression after multimodality therapy occurred in 10 patients. After retreatment, eight of these patients were alive at the time of analysis, with a median survival time after recurrence of 30 months. The 5- and 10-year overall survival rates for all patients were both 80.7%. The major side effect of CAMP therapy was acceptable neutropenia.

CONCLUSIONS

CAMP therapy was highly effective for invasive thymomas, and the multimodality therapy containing this chemotherapy brought about good disease control in the majority of patients. We believe that this multidisciplinary treatment with CAMP therapy, surgery, and radiotherapy is a justifiable initial treatment for patients with advanced invasive thymoma. Furthermore, appropriate treatments are essential for the long-term survival of patients with recurrences after multimodality therapy.

Thymoma: Benign Appearance, Malignant Potential

Thymoma is a rare tumor with a largely indolent growth pattern. It does, however, have malignant potential as a result of its ability to invade locally and metastasize regionally. Often associated with a number of immune- and nonimmune-mediated paraneoplastic syndromes, patient outcomes are directly related to stage of disease and the ability to achieve a complete surgical resection. Surgery is the mainstay of treatment, with adjuvant radiation recommended for invasive thymoma. Sensitive to both chemotherapy and radiation, durable responses are achievable in incompletely resected and inoperable patients. We present two cases of thymoma followed by a general discussion with an emphasis on treatment for both early and advanced-stage disease.

Prognostic Factors in Thymic Epithelial Tumors Undergoing Complete Resection

BACKGROUND

The prognostic factors in thymic epithelial tumors (TET) are investigated within a 27-year period in 104 patients submitted to surgical and pathologic complete resection of TET with a mean age of 53 +/- 14.6 years and a male to female ratio of 0.73.

METHODS

The medical records of all patients were reviewed and six variables that could affect the short-term and long-term survival were entered into a Cox regression model. Follow-up was obtained from medical records and telephone contacts up to September 2004 or until the patient's death.

RESULTS

Overall 5-year and 10-year survival was 83% and 78%, respectively. Univariate Cox regression analysis showed that long survival was affected by the age of the patient at the time of operation, the response of myasthenia gravis to the operation, the tumor recurrence, the histologic type according to the World Health Organization (WHO) classification, and the Masaoka stage. Multivariate analysis revealed that recurrence of the tumor (p = 0.001), Masaoka stages II or III (p < 0.001), elder age of the patient at the time of operation (p = 0.045), and presence of the WHO histologic types B2 or B3 (p = 0.05) were bad prognostic factors.

CONCLUSIONS

Recurrence of the tumor, the Masaoka staging, the WHO histologic type, and the age of the patient at the time of operation were the most important prognosticators for patients with TET submitted to complete resection of their tumor.