Malignant thymoma: current status of classification and multimodality treatment

Brain metastases from a thymoma: Case report for a rare secondary localization

Thymomas are benign epithelial neoplasms originating from the thymus gland and are among the most common primary mediastinal tumors. Malignancy is typically determined by evidence of pathological invasion beyond the capsule, with local invasion being the primary mode of spread to adjacent organs. Distant metastases are exceedingly rare. We present the case of a 63-year-old man who exhibited symptoms suggestive of increased intracranial pressure and motor deficit. Brain imaging revealed multiple intracranial lesions. Surgical intervention was performed to excise the largest lesion. Subsequent body CT scan and pathological examination confirmed that the brain metastases originated from a primary thymoma, classified as B3. The patient was recommended for adjuvant chemotherapy and radiotherapy, but unfortunately passed away at the initiation of therapy. The prognosis for patients with brain metastases from thymomas remains poor. Optimal management strategies typically involve prompt surgical intervention whenever feasible, followed by adjuvant therapy aimed at improving mean survival rates.

"An Unusual Pattern of Metastasis" Metastatic Malignant Thymoma Presented with Breast Lump: A Case Report and Literature Review

Metastatic lesions to the breast from extramammary malignant neoplasms are rare and reported account for 0.5-6.6% of all breast malignancies. Distant metastasis of thymoma is even rarer, especially to extrathoracic regions. We reported a woman with invasive malignant thymoma postneoadjuvant and resection of the thymoma, who developed breast metastasis 7 years later. Breast imaging showed high-density lesion with no intralesional microcalcifications and no significant axillary lymphadenopathy. Core biopsy and histopathology proved the lesion to be metastatic thymic carcinoma. Despite rarity, breast lumps with underlying extramammary malignancy should raise the suspicious of breast metastasis.

Thymic Carcinoma With Multiple Paraneoplastic Disorders

Thymic neoplasms are rare and may run an indolent course. Among them, thymic epithelial carcinoma is exceptional as it may be presented with extensive local invasion and distant metastases. There is a wide spectrum of autoimmune/paraneoplastic syndromes associated with thymic tumors including autoimmune diseases, some of which may precede the diagnosis of thymoma. This article describes a 37-year-old woman with metastatic malignant thymoma and a combination of manifestations from different organs. Vitiligo, Raynaud's phenomenon and anti-centromere antibodies were preceded while eosinophilia, interstitial lung disease, rash, thickening of the skin and asymptomatic cryoglobulinemia were diagnosed concomitantly with the neoplasm. We have reviewed the literature and found only twenty case reports with a cluster of three or more autoimmune/paraneoplastic syndromes in the same patient but none with this unique constellation of disorders. The diversity of thymoma's clinical presentation and laboratory/histological features may cause diagnostic dilemmas and therapeutic challenges.

[Case report of an osseous (and lymphogenic) thymic carcinoma in an adult]

A Thymic carcinoma in adults is rare. We present the case of a 47-year-old man, who was treated conservatively for spondylolisthesis L5/S1 in our institution for several years. In the further course, the patient complained about pain exacerbation with acute lower back pain. Cross-sectional scanning showed a tumor of the lumbar vertebral body three. A biopsy of this mass revealed a metastatic thymic carcinoma of the squamous cells. After palliative therapy, the patient died 9 months after initial diagnosis.

Thymic carcinoma - a rare case report

Introduction

Thymic carcinoma is a rare, invasive mediastinal neoplasm with a tendency to metastasize. They constitute a heterogeneous group of tumors that present differently in terms of both behavior and prognosis.

Case report

We present a case of thymic carcinoma in a 55-year-old male patient known to suffer from Myasthenia gravis, whose chief complaints were fatigability, ptosis and coughing. All electromyography studies were done along with excision biopsy to reach the definitive diagnosis.

Results and conclusion

The histopathological diagnosis of Thymic carcinoma-Lymphoepithelial variant was established. Though no definite staging system exists for the thymic carcinoma, prognosis of the patient was ascertained by using Weissferdt-Moran system, Masaoka and Tsuchiya TNM staging systems. Involvement of the pleural and the pericardial structures leads to poor prognosis, though no distant metastases or lymph nodal metastasis were evident.

The effect of myasthenia gravis as a prognostic factor in thymoma treatment

OBJECTIVE:

Thymoma is a standard epithelial tumor. Though it is rare, it constitutes 50% of anterior mediastinal masses. Variety of immunological diseases may accompany thymoma; however, myasthenia gravis (MG) is the most frequently associated paraneoplastic syndrome. Most effective treatment for thymoma is complete surgical resection. In this study, impact of MG on prognosis of thymoma cases was examined.

METHODS:

Records of 61 patients who underwent surgery with diagnosis of thymoma between January 2003 and September 2016 were retrospectively reviewed. All cases were analyzed for data related to age, gender, complaint, localization of lesion, surgical procedure, histopathological diagnosis, stage, MG, and long-term follow-up results.

RESULTS:

Total of 58 cases were included in the study. Of those, 37 patients were male and 21 were female. Mean age was 48 years. While 24 cases of thymoma were accompanied by MG, 34 cases were not. Duration of follow-up ranged from 1 month to 155 months.

CONCLUSION:

It was found that in group with MG, 5-year survival rate was 87.5% while it was 82.4% in group without MG. Despite longer duration of survival in group of thymoma associated with MG, there was no significant statistical difference between groups (p=0.311).

Intraoperative imaging identifies thymoma margins following neoadjuvant chemotherapy

Near infrared (NIR) molecular imaging is useful to identify tumor margins during surgery; however, the value of this technology has not been evaluated for tumors that have been pre-treated with chemotherapy. We hypothesized that NIR molecular imaging could locate mediastinal tumor margins in a murine model after neoadjuvant chemotherapy. Flank thymomas were established on mice. Two separate experiments were performed for tumor margin detection. The first experiment compared (i) surgery and (ii) surgery + NIR imaging. The second experiment compared (iii) preoperative chemotherapy + surgery, and (iv) preoperative chemotherapy + surgery + NIR imaging. NIR imaging occurred following systemic injection of indocyanine green. Margins were assessed for residual tumor cells by pathology. NIR imaging was superior at detecting retained tumor cells during surgery compared to standard techniques (surgery alone vs. surgery + NIR imaging, 20% vs. 80%, respectively). Following chemotherapy, the sensitivity of NIR imaging of tumor margins was not significantly altered. The mean in vivo tumor-to-background fluorescence ratio was similar in the treatment-naïve and chemotherapy groups ((p = 0.899): 3.79 ± 0.69 (IQR 3.29 - 4.25) vs. 3.79 ± 0.52 (IQR 3.40 - 4.03)). We conclude that chemotherapy does not affect tumor fluorescence or identification of retained cancer cells at margins.

Thymoma exhibiting spontaneous regression in size, pleural effusion and serum cytokeratin fragment level: A case report

A 30-year-old man was admitted to Toho University Omori Medical Center for assessment of right chest pain and fever. Chest computed tomography (CT) revealed an anterior mediastinal tumor sized 11.0×6.0×5.0 cm, with right pleural effusion. The laboratory analysis revealed elevated white blood cell count (11,000/µl), C-reactive protein (4.1 mg/dl) and cytokeratin fragment (CYFRA; 12.7 ng/ml; normal, <2 ng/ml). The level of CYFRA in the pleural effusion was also markedly elevated (143 ng/ml). On the first day after admission (6 days after the initial CT), there was a mild regression on CT (10.0×5.5×4.4 cm; reduction rate, 26.7%), with decrease of the pleural effusion volume. A CT-guided needle biopsy was performed, but the findings were not conclusive, as most of the tissue was necrotic. Seven days later (13 days after the initial CT), a CT revealed further regression (9.5×5.4×4.2 cm; reduction rate, 34.7%) with disappearance of the pleural effusion. The patient was followed up on an outpatient basis. At 35 days after the initial CT, the tumor continued to shrink without treatment (8.0×3.6×3.0 cm; reduction rate, 73.8%) and the serum CYFRA level had decreased to 0.8 ng/ml, although it had not returned to normal levels. At 62 days after the initial CT, the patient underwent surgical resection. The resected specimen was diagnosed as thymoma (World Health Organization type B2; Masaoka classification, stage II), with prominent degeneration and necrosis. One possible cause of the spontaneous regression may be increased internal pressure, probably associated with rapid tumor growth, leading to massive necrosis with resulting chest pain, inflammatory reaction with pleural effusion and subsequent tumor regression. The serum CYFRA level may be a useful marker for the evaluation of the clinical course of thymoma with extensive necrosis.

Thymoma patients treated in a phase I clinic at MD Anderson Cancer Center: responses to mTOR inhibitors and molecular analyses

BACKGROUND

Thymomas and thymic carcinoma are rare tumors with no approved therapies. Our purpose was to analyze the molecular features and outcomes of patients referred to the Clinical Center for Targeted Therapy (Phase I Clinic).

METHODS

We retrospectively reviewed the medical records of consecutive referred patients with advanced/metastatic thymoma or thymic carcinoma

RESULTS

Twenty-one patients were identified (median age 52 years; 10 women; median number of prior systemic therapies = 2). Six of 10 patients (60%) treated with mTOR inhibitor combination regimens achieved stable disease (SD) ≥12 months or a partial response (PR). For patients treated on mTOR inhibitor regimens (N = 10), median time to treatment failure (TTF) was 11.6 months versus 2.3 months on last conventional regimen prior to referral (p=0.024). Molecular analyses (performed by next generation sequencing in seven patients and single polymerase chain reaction (PCR)-based assays in an additional six patients) showed diverse actionable mutations: PIK3CA (1 of 12 tested; 8%); EGFR (1 of 13; 8%); RET (1 of 7; 14%); and AKT1 (1 of 7; 14%). Of two patients with PIK3CA or AKT1 mutations, one was treated with an mTOR inhibitor-based regimen and achieved 26% regression with a TTF of 17 months.

CONCLUSION

Patients with advanced/metastatic thymoma or thymic carcinoma demonstrated prolonged TTF on mTOR inhibitor-based therapy as compared to prior conventional treatment. Heterogeneity in actionable molecular aberrations was observed, suggesting that multi-assay molecular profiling and individualizing treatment merits investigation.

An unusual case of superior vena cava syndrome caused by the intravascular invasion of an invasive thymoma

Superior vena cava syndrome (SVCS) is usually caused by extrinsic compression or invasion of the superior vena cava (SVC) by malignant tumors involving mediastinal structures. Although thymomas are well-known causes of SVCS, cases of SVCS caused by malignant thymomas protruding into adjacent vessels draining the SVC with thrombosis have been very rarely reported worldwide. We experienced a 39-year-old female patient with SVCS that developed after the direct invasion of the left brachiocephalic vein (LBCV) and SVC by an anterior mediastinal mass with a high maximum standardized uptake value on the chest computed tomography (CT) and positron emission tomography-CT. Based on these results, she underwent en bloc resection of the tumor, including removal of the involved vessels, and was eventually diagnosed as having a type B2 thymoma permeating into the LBCV and SVC. We present this case as a very rare form of SVCS caused by an invasive thymoma.

Invasive thymoma in a child: a rare case report

Thymomas are neoplasms of the anterior mediastinum and generally occur between the fourth and sixth decades of life. In children, they are rare, with few reported cases. We describe a 9-year-old boy with invasive thymoma treated successfully by surgery alone. The patient was previously healthy and under treatment for a community-acquired pneumonia. A chest radiograph showed an opacity at the left lung base, and thoracic computed tomographic scan showed a mass with thick walls and liquid content situated in the lingula with no cleavage plane with the mediastinum. The patient underwent a left anterolateral thoracotomy, which showed a mass extending from the anterior mediastinum, infiltrating the left upper lobe of lung, phrenic nerve, and pericardium. A left upper lobectomy and resection of the mediastinal mass and lymph nodes were carried out. The pathologic analysis showed it to be a type B3 fusiform-cell thymoma, infiltrating the left upper lobe and 1 peribronchial lymph node. A multidisciplined tumor group decided to observe the patient and followed with thoracic computed tomographic scans every 3 months. After 2 years of follow-up, the patient has no evidence of recurrent disease.

Thymoma calcification: is it clinically meaningful?

Among anterior mediastinal lesions, thymoma is the most common. Thymomas are tumors of thymic epithelial cell origin that are distinguished by inconsistent histological and biologic behavior. Chest imaging studies typically show a round or lobulated tumor in the anterior mediastinum. Calcifications in thymomas are classically punctuate or amorphous, positioned within the lesion. Chest computed tomography (CT) features suggesting higher risk thymoma consist of tumor heterogeneity, vascular involvement, lobulation, pulmonary nodules, lymphadenopathy, and pleural manifestations. Imaging findings have an imperfect ability to predict stage and prognosis for thymoma patients. Our objective is to highlight the clinical implications of thymoma calcifications on the diagnosis, clinical manifestation and prognosis. A pubmed and google search was performed using the following words: thymoma calcification, calcified thymus, mediastinal calcification, anterior mediastinal calcification, and calcified thymoma. After reviewing 370 articles, 32 eligible articles describing thymoma calcifications were found and included in this review. Although the presence of thymus calcifications was more common in patients with invasive thymomas, they were present in significant portion of non-invasive thymomas. The presence of calcifications was not a significant factor in differentiating between benign and malignant thymoma. As a result, the type, location, size or other characteristics of thymus gland calcifications were not relevant features in clinical and radiologic diagnosis of thymoma. The histopathological diagnosis is still the only possible way to confirm the neoplastic nature of thymoma. All types of thymomas should be evaluated and managed independently of the presence of calcifications.

Thymic carcinoma with primary spine metastasis

Thymic carcinomas (TC) are rare tumors, representing 0.2% to 1.5% of all malignancies, with extrathoracic metastases to liver, kidney and bone occurring in 1% to 15% of patients. Although TC exhibit highly aggressive biological behavior, spinal metastasis with cord compression is rare. We describe a 57-year-old man with a 2-month history of cervicodorsal pain diagnosed with TC with primary spinal metastasis. We conclude that TC should be considered in the differential diagnosis in patients who have developed spine metastatic tumors. Early detection and appropriate surgical treatment can lead to preservation of spinal stability and neurologic improvement.

A population-based assessment of mortality and morbidity patterns among patients with thymoma

Thymomas are rare tumors of the mediastinum; a limited number of small studies have evaluated the outcomes in these patients. We identified 668 patients with thymoma from the Swedish Cancer Registry, and 2,719 population-based matched controls. We obtained information on autoimmunity from the nationwide inpatient/outpatient hospital discharge Registry. We constructed Kaplan-Meier curves for survival analysis, conditional regression and Cox proportional hazards models to evaluate the association between thymoma and autoimmune diseases, and standardized incidence ratios (SIRs) to evaluate the risk for second cancers following thymoma. Compared with controls, patients with benign or malignant thymoma had a poorer (p < 0.001) 5-year (79%, 53% vs. 91%), 10-year (65%, 39% vs. 78%) and 20-year (43%, 18% vs. 55%) overall survival. For thymoma patients, younger age at diagnosis and being diagnosed in recent years were associated with a better survival. Compared with controls, thymoma patients were more likely to have an autoimmune disease at some point during their lives (32.7% vs. 2.4%, respectively, p < 0.001), most frequently myasthenia gravis (24.5%), systemic lupus erythematosus (2.4%) and red cell aplasia (1.2%). Thymoma patients had twofold excess risk for second cancers compared with the general population, most notably: non-melanoma skin cancer (SIR = 10.6, 95% confidence intervals (CI) = 6.0-17.3), non-Hodgkin lymphoma (SIR = 6.8, 95% CI = 3.00-13.0), and cervical (SIR = 6.9, 95% CI = 1.4-20.1), endocrine (SIR = 4.7, 95% CI = 1.3-12.0), and prostate cancer (SIR = 3.0, 95% CI = 1.7-4.8). Despite the improved survival for thymoma patients over time, they have worse survival than controls. Thymoma patients are in need for follow-up to detect and manage autoimmune diseases and cancer.

Thymic carcinoma in children: a report from the Polish Pediatric Rare Tumors Study

BACKGROUND

Invasive thymomas and thymic carcinomas are rare tumors jointly accounting between 0.2% and 1.5% of malignancies in adults. They are usually at an advanced stage when diagnosed and have both high recurrence and poor survival rates. In this report, the aim is to explore our experience in the treatment of thymic carcinomas in Polish children.

PROCEDURE

The clinical data of nine children with thymic carcinomas, treated between 1992 and 2008 in the Polish oncological and surgical centers was retrospectively analyzed.

RESULTS

In five cases, presenting symptoms resulted from the compression of the respiratory ways by the mediastinal tumor. In two children paraneoplastic autoimmune syndromes were associated with thymic carcinoma. In accordance with the Masaoka classification, two patients had stage II, five had stage III, and two had stage IV of the disease. Diagnostic biopsy of mediastinal tumor was performed on eight patients and one underwent complete primary resection and subsequently received radiotherapy; he has passed 11 years since the conclusion of therapy. Six patients received multi-drug chemotherapy with or without steroids. Delayed surgery was performed in four children (R0-2, R1-1, and R2-1). After complete resection, one child received chemotherapy. In three patients, chemotherapy and radiotherapy was administered. Seven patients died, including six due to progression of the disease with the other as a result of complications following chemotherapy; only two patients classed at stage II remain alive.

CONCLUSIONS

Most thymic tumors in pediatric patients are inoperable at diagnosis, which results in poor prognosis. Improved chemotherapy approaches are needed.

Imatinib mesylate in patients with WHO B3 thymomas and thymic carcinomas

Thymic malignancies are rare tumors of the mediastinum. c-KIT is highly expressed in thymic carcinomas (TC) but infrequently in thymomas. Anecdotal experience suggests activity of imatinib mesylate in TC. Patients with unresectable World Health Organization B3 thymomas or TC, performance status 0 to 2, good organ function, and measurable disease were enrolled in this study. Imatinib was administered at 600 mg PO daily. Seven patients were recruited at one institution: two World Health Organization B3 thymomas and five TC. Imatinib treatment was generally well tolerated. Two patients had stable disease and five progressed. Median survival was 4 months, and median time to progression was 2 months. c-KIT expression was found in one of four samples by immunohistochemistry. No mutations were detected in the c-KIT or PDGFRA genes in three samples analyzed. Imatinib has no major activity in this rare tumor. Given the small number of patients treated in this study, selection based on presence of c-KIT mutations might be warranted.

The potentials of proton beam radiation therapy in malignant lymphoma, thymoma and sarcoma

A group of Swedish oncologists and hospital physicists have estimated the number of patients in Sweden suitable for proton beam therapy. The estimations have been based on current statistics of tumour incidence, number of patients potentially eligible for radiation treatment, scientific support from clinical trials and model dose planning studies and knowledge of the dose-response relations of different tumours and normal tissues. Besides sarcomas of the base of skull, which are classical sites for proton beam therapy, it is estimated that about 40 patients yearly in Sweden with sarcomas at other sites are candidates for proton beam therapy. About 20 patients each with malignant lymphomas, chiefly in the mediastinum, and thymomas are also candidates to decrease doses to surrounding heart and lungs.

Molecular pathology of thymic epithelial neoplasms

The etiology and molecular pathogenesis of thymic tumors are unknown. However, during the last two decades there has been some progress on elucidating the genetic abnormalities present and molecular pathways altered in thymic tumors. These abnormalities, while bearing distinctions and similarities to those described in other tumors, can be organized under the "hallmarks of cancer," as proposed by Hanahan and Weinberg. These changes include self-sufficiency in growth signaling, insensitivity to antigrowth signals, ability to evade apoptosis, limitless replicative potential, ability to sustain angiogenesis, and tissue invasion and metastasis. However, this progress is still limited and has not led to better tumor classifications, prognostication of outcome, and design of molecular targeted therapy.

Adjuvant Radiotherapy for Thymic Epithelial Tumor

OBJECTIVE

To determine whether the use of adjuvant radiation in the treatment of invasive thymic tumors affects survival and to identify prognostic factors.

METHODS

The files of 47 patients with thymic tumors treated by adjuvant radiation in our institute from 1984 to 2003 were reviewed for data on prognosis and survival. All patients underwent thoracotomy followed by either total macroscopic resection (n = 42) or biopsy (n = 5). The radiation dose ranged from 26 to 60 Gy.

RESULTS

Median duration of follow-up was 10.6 years. Overall 5-year survival was 73% (60%-88%): 77% for thymoma (n = 35/45) versus 33% for thymic carcinoma (n = 2/6) (P = 0.14). Better survival was associated with lower disease stage (II vs. III/IVA, P = 0.01), resection (P = 0.0004), myasthenia gravis at presentation (P = 0.04), and higher radiation dose (<or=45 vs. >45 Gy, P = 0.02); sex, smoking, tumor size, pathology, and margin status had no effect. Locoregional relapse occurred in 11 patients and distant metastasis in 4. The 5-year disease-free survival was 67% (52%-86%), with a median time to recurrence of 8.3 years. The better overall survival and disease-free survival associated with higher doses of radiation were also true for stage II patients. On multivariate analyses after adjusting for age, higher disease stage and lower radiation dose were found to adversely affect overall survival and disease-free survival. Thymic carcinoma had an impact only on disease-free survival.

CONCLUSION

Postoperative radiation therapy to doses above 45 Gy may improve the disease-free and overall survival of patients with invasive thymoma, especially stage II. Thymic carcinoma has a worse prognosis.

Total remission of thymus carcinoma after treatment with intravenous immunoglobulin

We report the case of a 42 year-old woman with myasthenia gravis associated with a malignant thymoma. Despite surgery, chemotherapy and radiotherapy, the thymoma showed soft tissues, pleural and mediastinic progression. Unexpectedly, a complete remission of the thymoma was confirmed by FDG-PET after four cycles of immunoglobulins, administered as treatment for a myasthenic crisis. To our knowledge this is the first case report of complete remission of a malignant thymoma with immunoglobulin therapy.

Systemic Treatment of Malignant Thymoma

OBJECTIVES

Thymic malignancies are rare tumors on the superior anterior mediastinum. Treatment of advanced stages includes chemotherapy. The objective of this analysis was to review the treatment of this disease in the past decade.

METHODS

This is a retrospective analysis of the results obtained in a total of 29 patients with advanced malignant thymomas who underwent systemic chemotherapy in the past 10 years at our institution. Sixteen received neoadjuvant chemotherapy in the attempt to shrink the tumor and then perform a radical operation. The others received chemotherapy as palliation. Platinum based chemotherapy was mainly used.

RESULTS

The response rate to first-line chemotherapy was 50% in the neoadjuvant setting and 31% in the advanced setting. A better survival was observed in patients who underwent chemotherapy as part of their combined modality treatment, in patients with thymomas, and in patients without visceral metastases. Some patients responded to targeted therapies at relapse.

CONCLUSIONS

A better understanding of the biology of this rare tumor may allow in the future the development of better therapies for the more aggressive tumor types (WHO type C), which appear to be increasing in frequency.

Symptomatic pituitary metastasis of malignant thymoma

Pituitary metastases from malignant thymoma are extremely rare. We report an 86 year-old-man with pituitary metastasis of malignant thymoma who complained of visual impairment and right ptosis. A pituitary lesion, which was partially removed by trans-sphenoidal surgery, was pathologically similar to the primary lesion and was diagnosed as pituitary metastasis of malignant thymoma. One autopsied case of pituitary metastasis of malignant thymoma has been found in the literature, and one case of this condition has been previously described in life. The present paper is the second report of symptomatic pituitary metastasis of malignant thymoma. Surgical removal of the pituitary lesion is a reasonable choice for the relief of progressive visual symptoms and for good quality of life in these patients.

Treatment of malignant thymoma

PURPOSE OF REVIEW

The present review reports findings in the field of epithelial tumors originating from the thymus from the past year and discusses these findings in the context of the literature.

RECENT FINDINGS

Epithelial tumors of the thymus are relatively common tumors of the anterior superior mediastinum. Thymomas are usually slowly growing tumors, and their prognosis depends on the macroscopic and microscopic invasion of surrounding tissues. Thymic carcinomas are more aggressive and less common tumors than thymomas and have been increasing in frequency in recent years. Surgery is the mainstay treatment of thymic malignancies, and complete resection represents the best prognostic factor in this disease. Postoperative radiotherapy may be indicated in tumors with invasion of surrounding tissues, but it is controversial in early-stage thymomas. Combination chemotherapy has been employed in several small studies and in advanced disease has been demonstrated to produce a 50-80% objective response rate. Neoadjuvant chemotherapy or external beam radiotherapy have been used with success in patients with tumors that are not readily resectable. Novel antiproliferative systemic agents are being investigated, based on a better understanding of the biology of these tumors.

SUMMARY

A better understanding of the clinical behavior of thymomas versus thymic carcinomas and systemic therapies targeted to biologically validated targets in these diseases will help improve efficacy of treatment.

Protein expression and gene amplification of epidermal growth factor receptor in thymomas

BACKGROUND

Epidermal growth factor receptor (EGFR) overexpression and amplification are important prognostic factors in many solid tumors and anti-EGFR antibody-based therapy is now available as a promising therapeutic modality. There is little information in the literature regarding the biologic role of EGFR in thymomas that are characterized by variable clinical presentations, histologic heterogeneity, and unpredictable behavior.

METHODS

Protein expression and gene amplification of EGFR were investigated in 32 thymomas (9 World Health Organization [WHO] type A, 5 type AB, 7 type B2, 7 type B3, 4 type C) using immunohistochemistry and fluorescence in situ hybridization (FISH). FISH analysis included assessment of the average number of copies of the EGFR gene per cell, the average ratio of the EGFR gene to chromosome 7 copy numbers, and ploidy.

RESULTS

The results of FISH analysis showed statistically significant correlation with WHO histologic type, invasion, advanced clinical stage, but not with tumor size and outcome. Thymomas associated with myasthenia gravis more frequently showed hyperploidy when compared with sporadic tumors, but there was no difference in EGFR gene amplification. EGFR protein expression assessed by immunohistochemistry did not correlate with any studied clinicopathologic variables. There was poor correlation between the protein expression and gene amplification, only 7 of 23 specimens (30%).

CONCLUSIONS

The potential role of EGFR in the pathogenesis of advanced-stage thymomas indicated that evolving anti-EGFR antibody therapy may be considered as a treatment option.

Tumor recurrence and survival in patients treated for thymomas and thymic squamous cell carcinomas: a retrospective analysis

PURPOSE

Thymic epithelial tumors (TET) are rare epithelial neoplasms of the thymus with considerable histologic heterogeneity. This retrospective study focused on the correlation of WHO-defined TET histotypes with survival and tumor recurrence in a large cohort of patients receiving different modes of treatment.

PATIENTS AND METHODS

Two hundred twenty-eight patients were followed for up to 21 years (median, 60 months; range, 1 to 252 months) after primary surgery. Forty-two patients received adjuvant radiotherapy (mean dose, 53 Gy), and 33 patients received adjuvant chemotherapy.

RESULTS

Seventy-six (88%) of 86 patients with WHO type A, AB, and B1 thymomas were treated by surgery alone, with three tumor relapses after 3 to 10 years (median, 3.4 years). Twelve of 67 patients with WHO type B2 and B3 thymomas in Masaoka stages I and II were treated by adjuvant radiotherapy without evidence of tumor recurrence after 1 to 12 years (median, 4 years). Among 75 patients with B2 and B3 thymomas with incomplete resection or a tumor stage III or higher, the recurrence rate was 34% (n = 23) after 0.5 to 17 years (median, 5 years) in patients receiving adjuvant radiochemotherapy, compared to 78% (seven of nine patients) in patients without adjuvant radiochemotherapy. Incomplete tumor resection was associated with a high recurrence rate (65%) and a poor prognosis (P <.01).

CONCLUSION

The long-term outcome of TET patients is related to tumor stage, WHO histotype, completeness of surgical removal, and type of treatment. Prospective trials are warranted to formally address the efficacy of adjuvant therapy in the treatment of localized and advanced malignant TETs.