Recurrent thymoma: evidence for histological progression

Combined Thymic Epithelial Neoplasms - a Review

Thymic epithelial neoplasms are the most common tumors of thymic origin but are overall rare in the general population. Their morphologic diversity, ranging from low grade to overtly malignant lesions, along with various histologic growth patterns make them a diagnostically challenging group of tumors. Very occasionally, thymomas and thymic carcinomas may develop in combination with other benign or malignant lesions of thymic origin, further complicating the diagnostic process. The focus of this review lies on the spectrum of thymic epithelial tumors that present with other thymic lesions in the same tumor mass, such as multilocular thymic cysts, neuroendocrine neoplasms, lymphomas, and germ cell tumors among others. Awareness of the existence of such unusual tumors may not only aid in their diagnosis but may also have implications for prognostic and therapeutic purposes.

Intrathoracic myolipoma from parietal pleura with oestrogen and progesterone receptor

Myolipoma is a rare benign lipomatous soft tissue neoplasm, occurring most frequently in adults in the abdomen, pelvis or retroperitoneum. We presented a case of a 39-year-old female with an epipleural lesion at the left paraspinal region identified using computed tomography. Magnetic resonance imaging revealed a fat-containing lesion attached to the pleura over the left paraspinal region. Surgical resection was performed, and histopathological analysis revealed a tumour composed of interlacing bundles of neoplastic smooth muscle cells with low cellularity and rare mitotic figures intermixing with mature adipocytes. The presence of oestrogen and progesterone receptors in smooth muscle cells was noted. The mass was reported as myolipoma. To the best of our knowledge, this case is the first description of an intrathoracic myolipoma.

De novo thymic carcinoma or malignant transformation: a myasthenic patient presented with multiple mediastinal tumours

A 63-year-old man presented with bilateral ptosis, and detailed evaluation confirmed ocular myasthenia gravis with three anterior mediastinal masses on computed tomography (CT) of the chest. Extended thymectomy was performed, and pathology revealed two thymic carcinoma and one thymoma. After surgery, the patient is free from recurrence. Synchronous triple thymic carcinomas and thymoma have not been reported. The finding of this case report supports the hypothesis of malignant transformation of thymoma to thymic carcinoma. Thymic carcinoma should be considered in the differential diagnosis of multiple thymic tumours, and extended thymectomy should be the treatment of choice.

Multimodality treatment of stage II thymic tumours

BACKGROUND

Complete resection for stage II thymic tumors can be easily accomplished even if the capsula and adjacent mediastinal tissue are macroscopically involved; however, also at this stage, recurrence may occur, particularly for B2, B3 and thymic carcinoma. The criteria for the administration of adjuvant therapy remain controversial and it is unclear whether patients at this stage may benefit from it. We reviewed a series of patients at this stage receiving adjuvant chemo-radiotherapy (chemo-RT) based on histology.

METHODS

Eighty-eight consecutive patients with stage II thymic tumors were reviewed; 59 patients (67%) with B thymoma or thymic carcinoma received adjuvant treatment with mediastinal irradiation (40-55 Gy), chemotherapy (CH) (PAC regimen) or a combination of both.

RESULTS

Complete resection was achieved in all patients. Fifty-four patients (61%) received post-operative chemo-RT, 2 (2%) patients received adjuvant CH only and 3 (3%) post-operative RT only; they all had B2, B3 histology or thymic carcinoma. The median follow up was 107±83 months. 5-year and 10-year survival were 96%±2% and 83.4%±5%. Recurrence was observed in 5 patients (5.7%). Disease-free 5 and 10-year survival was 94%±2% and 92%±3% respectively. Five patients (5.7%) had recurrence.

CONCLUSIONS

The administration of adjuvant chemo-RT to patients with stage II type B thymoma and thymic carcinoma contributes to reduce the recurrence rate and to increase long-term survival.

Long-term results after treatment for recurrent thymoma: a multicenter analysis

OBJECTIVES

The treatment for recurrent thymoma remains a very controversial issue. This study aims to investigate the long-term outcomes in patients with relapse according to treatment strategies and clinicopathological features.

METHODS

We retrospectively analyzed the database of three tertiary centers of thoracic surgery with the aim of reviewing the clinical records of 81 patients who experienced a recurrent thymoma after radical thymectomy, in the period between January 2001 and June 2013. The staging of both primitive and recurrent thymomas were based on the surgical and pathological criteria described by Masaoka. Experienced pathologists reassessed independently the histology of the initial thymoma and its relapse, according to the WHO classification. To the purposes of this study R+ resection or thymic carcinoma were considered as exclusion criteria. The overall outcome for long-term (5 years and 10 years) survival and disease-free survival after initial thymectomy and after treatment of recurrent thymoma were analyzed using standard statistics.

RESULTS

The population was gender balanced (41 M, 40 F), mean age: 46.4 ± 12.3 years. Fifty-four patients (66.7%) were affected by myasthenia gravis, while the other 14 by other paraneoplastic conditions. Surgery was performed in 61 patients (75.3%,), and radiotherapy and/or chemotherapy in 14 patients (17.3%). The mean follow-up duration after recurrence onset was 66.3 ± 56.4 months. Adjuvant therapy had no effect on prolonging the disease-free survival: no differences were found when investigating the administration of adjuvant chemotherapy (no CHT = 91.5 ± 76.4 months versus yes CHT=64.0 ± 41.3) and radiotherapy (no RT=86.2 ± 72.8 months versus yes RT= 93.0 ± 62.3; p = 0.8). Relapses were mostly local (mediastinum: 15 cases, pleura: 44 cases); hematogenous distant recurrences were observed in 15 cases (lung: 12; liver: 1; bone: 2 cases). An upgrade in the WHO class (defined as the "migration" of WHO class at initial thymectomy to more aggressive WHO class assigned at thymic recurrence resection) was found in 25/61 cases (40.9%), but this phenomenon apparently did not influence patient's prognosis. Overall, the 5- and 10-year survival rates after the initial thymectomy were 94.8% and 71.7%, respectively, while the 5- and 10-year survival rates after the treatment of the recurrence at the thymic level were 73.6% and 48.3%, respectively (82.4% at 5 years and 65.4% at 10 years when a R0-re-resection was obtained). The analysis on the trends of disease-free survival indicated that the site of recurrence (hematogenous diffusion) seems to be associated to a higher risk of re-relapse (p = 0.01).

CONCLUSIONS

Even following a thymectomy performed with radical intent, thymoma may recur several years later, usually as a locoregional relapse. A rewarding long-term survival may be expected after treatment, especially when a re-resection (radical) is performed (82.4% at 5 years). An histopathological "WHO upgrade" (from "low-risk" WHO classes at thymectomy to "high-risk classes" at relapse) may be observed in a remarkable percentage of patients (nearly 40% in this series), but this phenomenon seems to be not correlated with any worsening of the prognosis.

Solitary metastasis to the breast after complete resection of encapsulated type AB thymoma: a case report

INTRODUCTION

Type AB thymoma is generally considered a benign tumor with excellent prognosis. Rare case reports of type A and AB thymomas with recurrence and metastasis have been documented, although extrathoracic metastases are extremely rare. To the best of our knowledge, this is the first reported case of type AB thymoma with solitary metastasis to the breast.

CASE PRESENTATION

We describe an 83-year-old Taiwanese woman with a metastatic thymoma to the breast 10 years after complete resection of noninvasive and encapsulated primary tumor, and analyze the possible factors to explain the recurrence and metastasis of the stage I thymomas.

CONCLUSIONS

Even a clinically benign tumor such as type AB thymoma still has a possibility of metastasizing to an unusual site. When any uncommon tumor presents in any site, a suspicion of secondary neoplasm and thorough clinical history are required.

Extrathoracic metastases of thymic origin: a review of 35 cases

Thymic tumors are categorized as types A, AB, B1, B2, B3, and thymic carcinoma under the World Health Organization (WHO) classification. Thymomas are typically slow growing tumors that predominantly involve the surrounding structures through direct invasion, while thymic carcinomas tend to be more aggressive. A significant number of patients are asymptomatic and can present with metastases as the first presentation. The exact incidence of extrathoracic metastases from thymoma is not known. This study describes a series of 35 cases of histologically documented metastatic thymomas and thymic carcinomas at extrathoracic sites. These cases were classified according to the current World Health Organization (WHO) classification criteria, and we present their clinical data as well as discuss the differential diagnoses of these lesions. Our study shows that all types of thymic tumors, regardless of histologic type, can be associated with invasion and metastases to thoracic and extrathoracic sites.

A malignant retroperitoneal mass--a rare presentation of recurrent thymoma

A 60-year-old man presented with a suspected retroperitoneal mass, after primarily resected thymoma (type B1/B2, Masaoke stage 1). A germ cell tumour was excluded and a diagnostic biopsy was performed. The mass appeared to be a local recurrence of the primary thymoma, for example, a droplet metastasis, progressed to type B3.

Management of pleural recurrence after curative resection of thymoma

OBJECTIVE

A complete surgical resection is the cornerstone of therapy of thymic tumors. Unfortunately, there is no standard treatment for pleural recurrence. This article describes our overall experience with the surgical treatment of pleural implants in patients who previously underwent resection of a thymoma.

MATERIAL AND METHODS

From January 1980 to June 2006, 20 patients previously operated on for a thymoma were operated on for the surgical resection of pleural implants. Patients with the initial Masaoka stage IVA were excluded from our analysis. Our sample comprised 10 male and 10 female patients (12-65 years old). The surgical approach to the resection of the thymoma was as follows: video-assissted thoracic surgery in 2 patients, sternotomy in 13 patients, thoracotomy in 2 patients, and sternothoracotomy in 3 patients. The initial Masaoka stage of the thymoma was IIA in 2 patients, IIB in 7 patients, and III in 11 patients.

RESULTS

The interval between resection of the thymoma and pleural implants ranged from 11 to 156 (median 60) months. Fifteen patients had a thymus-related syndrome (in 13 patients it resulted myasthenia gravis), and in 11 patients it improved or remitted after treatment of the pleural recurrence. All the resections were performed through a posterolateral thoracotomy. Three patients underwent an iterative resection of new pleural implants. At the latest follow-up, 10 patients are still alive (8 disease-free) and 10 have died (9 of a relapse and 1 of the complications of red cell aplasia). From the pleural recurrence resection, the overall 5- and 10-year survivals are 43.1% and 25.8%, respectively.

CONCLUSIONS

Repeat operation on patients with thymoma pleural recurrences is feasible and safe. It can produce satisfactory results in terms of overall survival and paraneoplastic syndrome control. Moreover, the multimodality treatment could improve the results of surgical treatment.

Histologic classification of thymoma: the World Health Organization and beyond

Thymoma classification has remained for many years a troubled and contentious field. In recent years, the World Health Organization (WHO) presented a proposal for the histopathologic classification of thymic epithelial neoplasms that has been adopted as the standard by many pathologists throughout the world. Yet, controversy still exists regarding its validity, accuracy, usefulness, and reproducibility in routine clinical practice. This article reviews the basic criteria of the current WHO classification of thymoma, along with its weaknesses and limitations, and presents alternate proposals for the histopathologic approach to the classification of thymic epithelial neoplasms.

Treatment of recurrent thymic tumors

Surgery is the cornerstone of therapy for recurrent thymic tumors. The pattern of recurrence is, however, less defined. Between 1966 and 1988, we operated on 83 patients with thymoma, 11 of whom underwent surgery for recurrence (group I). In 1989, we initiated a prospective multimodality protocol and have enrolled 128 patients with 9 (7%) recurrences since (group II). In group I, 1 patient was originally at stage I, 2 were at stage II, 5 at stage III, and 3 at stage IV. The patients underwent 1 (#10) or 2 (#1) reoperations and 5 showed histological progression of malignancy. One patient died postoperatively, 6 died of disease, and 3 are alive and disease free 18 to 22 years after the first operation. In group 2, no patient was originally at stage I, 1 was at stage II, 4 were at stage III, and 4 at stage IV. Reoperation (5 patients) was followed by chemotherapy and 2 showed histological progression of disease. One patient died after 2 years, and 4 patients are alive after 6 to 11 years. All recurrent tumors were thymomas with cortical differentiation. Early onset of recurrence was a negative prognostic factor. Thymomas can recur also at early stages. A multimodality approach is indicated also for early stage lesions based on histology.

Atypical thymoma: A report of seven patients

BACKGROUND

Most thymic neoplasms fall under the designation of thymoma, consisting of well-differentiated epithelial cells, resembling normal thymus. At the opposite spectrum are thymic carcinomas; the cell of origin while similar is malignant. Recently a third category of thymic neoplasms, atypical thymomas, has been recognized representing thymic neoplasms manifesting atypia although without overt cytomorphologic criteria of malignancy.

METHODS

Seven patients with a diagnosis of atypical thymoma were encountered over a 6-year period from the patient files of the cardiothoracic division of The Ohio State Medical Center.

RESULTS

In all patients there was gross or light microscopic invasive disease with involvement of the capsule, phrenic nerve, diaphragm, chest wall, and lung. Surgical extirpation/de-bulking along with radiation therapy in six and chemotherapy in one led to complete disease regression. Intrathoracic recurrences developed in 4 involving lung, pleura, chest wall and diaphragm. All patients are well.

CONCLUSIONS

Atypical thymomas are locally aggressive tumors with a high incidence of intrathoracic recurrence; extrathoracic spread is not seen. Our study corroborates other reports that death attributable to atypical thymoma is uncommon.

Thymoma--the usefulness of some prognostic factors for diagnosis and surgical treatment

AIMS

The aim of the study was to identify prognostic factors which could help evaluate both the treatment offered to patients with thymoma and late results.

METHODS

Forty patients were treated for mediastinal thymoma. The patients were staged clinico-pathologically (according to Masaoka) on the basis of the retrospective analysis of their operation protocols as follows: seven (17.5%)-stage I, 19 (22. 5%)-stage II, 17 (42.5%)-stage III, seven (17.5%)-stage IV. Analysis of DNA contents in cell nuclei of 23 thymomas was performed by the flow cytofluorometric method.

RESULTS

From the whole group of patients, 65% survived for 5 years, 55% survived for 10 years and 43% survived for 15 years. We noted significant differences in survival time between stage I and stage IV (P<0.0012); stage II and stage IV (P<0.0006), as well as between stage III and stage IV (P<0. 005). Significantly worse prognosis was observed in the case of cortical thymomas as compared with medullary or mixed types (P<0. 0001 P<0.002). Analysis of DNA content showed signficantly higher probability of survival for the patients who had DI=1.0 (diploid), as compared with DNA >1.0 (aneuploid) (P<0.006). Of the 11 patients with diploid tumours, 91% survived for 5 years, but of the 12 aneuploid, only 23% survived.

CONCLUSION

The most important positive prognostic factors influencing survival rate in patients with thymoma are: lower stage, medullary type (according to Muller-Hermelink classification), possibility of performing complete resection, diploidal nature of the tumour. Multivariate analysis of survival revealed clinico-pathological stage (according to Masaoka) and histological type (according to Salyer) as significantly independent prognostic factors.

Recurrence of stage I thymoma 32 years after total excision

Malignant thymomas are invasive and recur frequently, but noninvasive thymomas rarely do so. We report on a case of recurrent thymoma in a 50-year-old white man, 32 years after total excision of a stage I thymoma. We stress the importance of long-term follow-up in all patients.

Primary thymic epithelial neoplasms showing combined features of thymoma and thymic carcinoma. A clinicopathologic study of 22 cases

Thymic epithelial neoplasms are unusual tumors that may span the gamut from clinically benign, well-differentiated lesions (encapsulated thymoma) to overtly malignant, poorly differentiated neoplasms (thymic carcinoma). It has been commonly believed that lesions displaying obvious cytologic features of malignancy (i.e., thymic carcinoma) represent a unique and separate group that is histogenetically distinct from thymoma. We have studied 22 cases of thymic epithelial neoplasms characterized by the admixture of areas displaying conventional features of thymoma with areas showing features of thymic carcinoma. The tumors occurred in six women and 16 men whose ages ranged from 23 to 83 years (median, 53). The lesions presented in eight patients with symptoms of chest discomfort resulting from the involvement of surrounding structures; in 14 patients, they were asymptomatic and discovered incidentally on routine chest radiographs. Histologically, most tumors showed a combination of conventional thymomatous elements with well-differentiated squamous-cell carcinoma (10 cases), followed by thymoma and poorly-differentiated squamous carcinoma (seven cases) and spindle-cell thymoma with poorly-differentiated squamous carcinoma (five cases). Areas of transition between the two different components could be identified in most cases. In five cases, areas showing the features of clear-cell carcinoma could be seen either arising from squamous carcinomatous elements or within the thymomatous component, and in one case transitions between lymphoepithelioma-like carcinoma and anaplastic carcinoma could be observed. Two patients had a history of myasthenia gravis with biopsy-proven thymomas in whom the tumors had been monitored without treatment for 10 and 14 years before the sudden enlargement of the mass. The resected specimens in both patients showed the emergence of a carcinoma arising from a thymoma. The present cases appear to support the existence of a continuum in the spectrum of differentiation between thymoma and thymic carcinoma, suggesting a close histogenetic relationship between these two conditions. Such findings are important not only for our understanding of these tumors but may also play a significant role in the assessment of the biologic behavior and management of these lesions.