Extrathoracic metastases of thymic origin: a review of 35 cases

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.

Thymic Adenocarcinoma With Metastasis to the Left Orbit: A Case Report

We present the case of a 57-year-old female who initially presented with a chief complaint of left-sided orbital headaches and associated left eyelid swelling. Initial imaging work-up with CT head/orbit revealed soft tissue enhancement of the left orbital roof, concerning for neoplastic process (primary lymphoma versus extracranial primary tumor versus metastatic tumor). Further imaging studies with CT chest/abdomen/pelvis revealed an anterior mediastinal mass, concerning for possible thymoma versus lymphoma. The patient underwent further consultation with the Hematology/Oncology and Ophthalmology Departments, which recommended definitive biopsies from both sites, which showed matching histologic findings of moderately differentiated enteric-type adenocarcinoma with positive staining for CDX2, an intestinal marker. Thymic carcinomas are rare cancers that account for approximately 0.06% of all malignancies and require a high degree of clinical suspicion. Extrathoracic metastases from thymic carcinomas, especially to the orbit, is a rare occurrence and the exact incidence of this phenomenon is unknown. This case represents the diagnostic challenges associated with a rare cancer type and underscores the importance of a multidisciplinary approach to patient care.

Transcaval and Intracardiac Extension of Type A Thymoma and Myxoma: A Report of Two Rare Cases

We report two cases of rare invasive tumors presenting with transvenous and intracardiac extensions. In one instance, an unusual invasive thymoma type A penetrated into the heart chamber; the other case was an extension of a myxoma into the right atrium that was associated with superior vena cava syndrome. Our interest was stimulated by the rarity of these clinicopathological observations and the unusual clinical features of diagnostic and therapeutic methods presented by these cases.

Thymoma metastatic to the epidural thoracic spine

Background

Thymomas rarely metastasize to the spine. Here, we present a 69-year-old female diagnosed with stage IV thymoma, which subsequently developed a symptomatic epidural thoracic spinal lesion causing thoracic myelopathy.

Case Description

The patient initially presented with paraspinal rib pain, lower extremity weakness, and gait imbalance. The magnetic resonance revealed a T10 vertebral body lesion with epidural extension causing severe spinal cord compression. A T9-T10 hemilaminotomy for tumor resection was performed; this was followed by adjuvant chemotherapy and radiation. Gross total resection was achieved, and the final pathology was metastatic thymoma. Postoperatively, the patient significantly improved.

Conclusion

Metastatic thymomas to the thoracic spine are rare. For those presenting with epidural lesions causing myelopathy, surgical resection is beneficial and may be accompanied by adjunctive radiation and chemotherapy.

Liver Metastasis of Thymoma: Case Report and Review of the Literature

The 2021 "World Health Organization (WHO) Classification of Thoracic Tumours" classifies epithelial tumors of the thymus (thymomas) based on cytomorphology. Thymomas with benign cytomorphology are classified as type A, AB, B1, B2, and B3, while those with malignant cytomorphology are classified as thymic carcinoma. Although all thymomas have malignant potential, extra-thoracic metastasis of thymomas is exceedingly rare and the exact incidence is not known. Literature review demonstrated 39 cases of thymoma with extra-thoracic metastases reported since the publication of the 1999 WHO Classification of Thoracic Tumours. Nine of these cases presented with metastasis to the liver in the setting of concurrent metastasis to other organs, while only three cases metastasized solely to the liver. We herein report a well-documented case of type B1 thymoma with relatively limited stage (IIb) with an isolated, single liver metastasis occurring seven years after primary resection in a patient with concomitant myasthenia gravis. The following report includes a review of the literature, a discussion of thymoma classification and its relevance to prognosis, and an overview of other extra-thoracic metastatic thymoma cases.

Spleen metastasis of recurrent malignant thymoma

Thymoma is a rare tumour that often occurs in the anterior mediastinum. Thymomas are usually diagnosed in middle-aged patients, and nearly half of cases are associated with myasthenia gravis. Thymomas typically progress through direct invasion of the thoracic cavity with extra-thoracic distant metastasis being uncommon. Here we report the case of a male patient who underwent an extensive thymectomy and radiotherapy 10 years before presentation, and in whom we detected a spleen tumour during regular out-patient follow-up. The patient underwent a splenectomy, and a final diagnosis of type B3 malignant thymoma was established.

Cutaneous Metastases from Thymic Carcinoma Primary Tumor: A Rare Case

Cutaneous metastases (CM) are neoplastic lesions of the skin originating from a primary tumor elsewhere. CM originating from primary thymic carcinoma is rare, and its incidence remains uncertain. A case of CM from thymic carcinoma in a 57-year-old man was reported. The patient complained about lumps on the skin of the chest, right shoulder and neck that appeared eleven months before the diagnosis of thymic carcinoma was established. Physical examination revealed tumors on the chest, right shoulder and neck. Histopathological examination results were consistent with CM. An immunohistochemical (IHC) examination was performed to determine the primary tumor, with a positive result for CK7. The diagnosis of thymic carcinoma was established based on the results of enhanced chest CT-scan and immunohistochemistry on lymph node biopsies. The patient was treated with a chemotherapy regimen of cyclophosphamide, doxorubicin, and carboplatin scheduled for six cycles. However, the patient did not survive his third cycle of chemotherapy. Establishing the diagnosis and managing CM are challenging for clinicians. This requires careful historical and physical examination, supported by histopathological examination and specific immunohistochemical marker in accordance with the suspected tumor.

Pleural Invasion Depth of Disseminated Nodules in Patients with Stage IVa or Recurrent Thymoma: Assessment, Curative Impact, and Surgical Outcomes

BACKGROUND

Thymoma patients with pleural dissemination are difficult to manage, and their treatment strategy remains undefined. This study aimed to investigate the clinicopathologic features of these patients, focusing on the association between the depth of pleural invasion and prognosis.

METHODS

Between 2003 and 2019, the study identified 120 disseminated lesions in 20 thymoma patients. Seven patients had de novo stage IVa thymoma and 13 were recurrent cases. Extrapleural pneumonectomy was performed for 8 patients and debulking surgery for 12 patients. Invasion depth of pleural tumors was classified into two groups: when the disseminated tumors invaded the pleura beneath the elastic layer, the tumor was diagnosed as Da, and when the disseminated tumors invaded the pleura beyond the elastic layer, the tumor was diagnosed as Db.

RESULTS

Of 120 nodules, 31 (26%), found in eight patients with recurrent malignancies, were classified as Db. The pathologic status of the surgical margin (PSM) was positive in eight patients, seven of whom had Db nodules. The 5-year overall survival (OS) rate was 100% in the Da group and 75% in the Db group (P = 0.02). The 5-year progression-free survival (PFS) rate was 66.7% in the Da group and 25% in the Db group (P = 0.02). Cox univariate analysis showed that PFS was significantly influenced by the depth of invasion (P = 0.04) and PSM (P = 0.03).

CONCLUSION

Depth of pleural invasion may influence survival outcomes for thymoma patients with pleural dissemination. The patients in this study with Da-disseminated nodules had an increased probability of a longer OS and PFS and tended to achieve negative PSM compared with the patients with Db.

A rare case of hepatic metastasis 20 years after surgical resection of a thymoma: A case report

INTRODUCTION

Thymoma is the most common solid, primary mediastinal tumour, accounting for 20% of mediastinal neoplasms. Malignant thymus tumours (thymomas and thymic carcinomas) metastasize primarily locally. Distant metastases, especially to liver are very rare.

PRESENTATION OF CASE

We review the case of a 59 year-old female patient, who underwent resection of the thymus with a diagnosed type B2 thymoma 20 years ago. The patient was referred to our hospital with a newly discovered space-occupying lesion in the liver, which had been detected in a routine follow-up magnetic resonance imaging scan. Since a malignant tumour of the liver could not be excluded, a conventional left hemihepatectomy was performed. Histological examination revealed a liver metastasis of the type B2 thymoma, which had been removed 20 years ago.

CLINICAL DISCUSSION

The case was discussed in the interdisciplinary tumour board. Based on the very long history of the primary removal of the thymoma as well as the R0 resection of the liver metastasis, a follow-up regimen with CT scans on a regular basis was recommended.

CONCLUSIONS

Newly discovered lesions of the liver in patients even with a long history of a thymoma should raise the suspicion of a liver metastasis that should be surgically resected as the therapy of choice. Further, this case indicates the importance for long-term radiographic follow-up.

Central Nervous System Metastases in Thymic Epithelial Tumors: A Brief Report of Real-World Insight From RYTHMIC

Thymic epithelial tumors (TETs) are rare malignancies ranging from indolent thymoma A to aggressive thymic carcinomas (TCs). Brain metastases are extremely infrequent for TETs and have only been described in case reports or small single-center series. RYTHMIC (Réseau tumeurs THYMiques et Cancer) is a French nationwide network mandated to systematically review every TET case and prospectively includes all consecutive patients discussed by national or regional tumor boards. We analyzed patients with TETs and central nervous system (CNS) metastasis during their cancer history from this large French registry. In an 8-year period, 2909 patients were included in the database, including 248 TCs (8.5%). A total of 14 patients had CNS metastases, five (36%) at diagnosis and nine (64%) at relapse. Among them, 12 patients (86%) had a diagnosis of TC and two (14%) had thymoma A and B3. Surgical biopsies were performed, and the histologic subtype for non-TC tumors was centrally confirmed. Median overall survival was 22 months (95% confidence interval [CI]: 9.8-34.2), with longer, albeit not significant, overall survival when CNS metastases were present at diagnosis versus relapse (not reached versus 17 mo; p = 0.29); median progression-free survival was 13 versus 8 months (p = 0.06), respectively. A higher risk of death (hazard ratio = 5.34, 95% CI: 1.3-21.9, p = 0.02) and relapse (hazard ratio = 1.89, 95% CI: 0.9-3.7, p = 0.06) was observed for patients suffering from TC with brain metastases compared with those without CNS extension. CNS disease was extremely rare in our TET cohort (0.48%), reported at both diagnosis and progression, present primarily in TC, with prevalence rising to 4.9%.

Budd-Chiari syndrome caused by latent hepatic metastasis from a thymoma

A 34-year-old woman visited our hospital because she had had abdominal bloating for 2 months. She had been diagnosed with invasive thymoma (WHO pathological type B2), for which she had undergone chemotherapy and total thymectomy 10 years previously. Six years previously, pleural dissemination was diagnosed and she had undergone right extra-pleural pneumonectomy. On presentation to our hospital, abdominal computed tomography and ultrasound scans revealed abundant ascites and a huge liver lesion, likely a metastasis from her thymoma, obstructing the inferior vena cava. The serum-ascites albumin gradient was high at 1.4 g/dL, which indicated portal hypertension. We diagnosed Budd-Chiari syndrome caused by liver metastasis from a previous thymoma. Steroid therapy resulted in shrinkage of her liver tumor and a marked decrease in her ascites. Although rare, Budd-Chiari syndrome caused by liver metastasis from a thymoma is a possible serious complication of advanced invasive thymoma.

Dural venous sinus tumour thrombus from metastatic thymoma

Thymomas are the most common primary tumours of the anterior mediastinum. While intrathoracic disease progression through local invasion is well described in the literature, extrathoracic extension of disease is uncommon and intracranial metastases have seldom been reported. We present a case of extensive dural venous sinus tumour thrombus in a patient with metastatic invasive thymoma.

Fibrous bands associated with higher Masaoka stage and poor recurrence-free survival in patients with thymoma

Background

Fibrous bands (FBs) are one of the histological features in tumors which can be confirmed by hematoxylin and eosin (H&E)‐stained slides. FBs have been reported to correlate with malignancy in various tumors. This study aimed to investigate whether the presence of FBs is associated with malignancy in thymoma.

Methods

A total of 123 consecutive patients with thymoma who underwent microscopically complete resections from January 2000 to December 2018 were enrolled into this study. H&E‐stained slides of all thymoma patients were re‐examined. Study patients were classified into two groups: with FBs (n = 36) and without FBs (n = 87). Clinicopathological characteristics, overall survival (OS), and recurrence‐free survival (RFS) were compared between the two groups. Furthermore, multivariate analyses were performed to identify whether the presence of FBs was associated with higher Masaoka stage and poor prognosis in patients with thymoma.

Results

The Masaoka stage was found to be higher and recurrence more likely in thymoma patients with FBs than in those without. RFS was significantly poorer in thymoma patients with FBs than in those without, although no significant difference was observed in OS between them. The presence of FBs was significantly associated with higher Masaoka stage in the multivariate analysis using logistic regression. Additionally, the presence of FBs was an independent prognostic factor for poor RFS in multivariate analysis using Cox's proportional hazards model.

Conclusions

The presence of FBs in patients with thymoma was associated with higher Masaoka stage, higher recurrence rate, and poorer RFS.

Key points

Significant findings of the study

Fibrous bands (FBs) are bands of fibrosis dividing tumors into different‐sized irregular islands. The presence of FBs is associated with higher Masaoka stage and poor recurrence‐free survival in patients with thymoma.

What this study adds

The presence of fibrous bands might be associated with the malignant behavior of thymoma. Confirming the presence or absence of FBs may result in personalized medication for patients with thymoma.

Treatment strategy and prognostic analysis of spinal metastases from thymomas: A retrospective study from a single center

OBJECTIVE

Thymomas are rare in clinical practice, and cases of metastatic spinal thymoma are extremely scarce, with only a few case reports or case series described in the literature. In this study, we characterized the clinical features, treatment options and prognostic analysis of patients with metastatic spinal thymomas.

PATIENTS AND METHODS

This study included seven patients with metastatic spinal thymoma who underwent open surgery or minimally invasive surgery, and adjuvant treatment in a single center of Peking Union Medical College Hospital from 2010 to 2019. The basic clinical data of the patients were analyzed retrospectively. The possible prognostic factors of progression-free survival (PFS) and overall survival (OS) were studied using the Kaplan-Meier method.

RESULTS

This retrospective study included six male patients and one female patient, with a median age of 58.4 (47-75) years. The time from initial diagnosis to detection of spinal metastasis was 54.2 (30-108) months. Kaplan-Meier survival analysis showed the number of spinal metastasis and adjuvant therapies were favorable factors for improving OS and PFS in patients with metastatic spinal thymomas.

CONCLUSION

Radiation therapy after the primary operation is an efficient adjuvant therapy, since patients who received postoperative radiation treatment have longer OS and PFS than those who receive chemoradiotherapy. The number of spinal metastases seems to be an effective prognostic factor for longer OS and PFS of patients with spinal metastasis of thymoma.

Low-Grade Thymoma with Osseous and Pulmonary Metastases: Role of 18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography in Initial Staging

Thymomas are rare anterior mediastinal tumors that originate in the epithelial cells of the thymus and have a rare propensity to metastasize to extrathoracic locations unless it is a histologic high-grade neoplasm (type B and above). We describe a case of 50-year-old woman diagnosed with type AB thymoma and the role of ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography in accurate delineation of extrathoracic metastases during initial staging.

Successful treatment of combined thymic epithelial tumor with hepatic metastasis: a long disease-free survival case

A 73-year-old man presented with multiple liver nodules on an abdominal echogram. Fluorine-18-fluorodeoxyglucose (FDG)-positron emission tomography computed tomography (PET-CT) showed multiple nodules in his anterior and posterior mediastinum, and liver. Following thymothymectomy with lymph node dissection, the liver nodules were completely resected. Finally, he was diagnosed with combined thymic tumor (small cell carcinoma and type B3 thymoma) with multiple mediastinal lymph nodes and liver metastases by type B3 thymoma. Follow-up PET-CT scan revealed multiple rib and celiac lymph node metastases, six courses of chemotherapy (paclitaxel and carboplatin) were administered, and the patient survived without any recurrence for 15 years after initial surgery.

Thymoma dissemination through the thoracic intervertebral foramen: Pleural recurrence resulting in spinal cord compression

Background:

Spinal dissemination of thymic tumors is rare but should be considered in the differential diagnosis of thoracic dumbbell-shaped lesions and/or vertebral tumors, irrespective of the time since the initial diagnosis.

Case Description:

A 63-year-old man, with a history of invasive type AB thymoma treated 21 years ago, newly presented to the hospital with a dumbbell-shaped T8-T9 lesion compressing the spinal cord. A review of the literature showed only 16 previous cases of thymic tumors with thoracic spine involvement. Here, we report the lengthiest interval between the initial tumor diagnosis and the detection of spinal involvement, that was secondary to a pleural recurrence from his thymoma. The patient did well following successful excision of the intraspinal mass which had encased the T8 nerve root.

Conclusion:

Spinal dissemination of thymic tumors can occur due to vertebral metastasis or to extension of a pleural recurrence through the intervertebral foramen. Definitive treatment for spinal lesions should be considered to provide adequate cord decompression.

Surgical management of spinal metastases of thymic carcinoma: A case report and literature review

RATIONALE

Metastatic thymic carcinoma in the spine is a rare disease with no standard curative managements yet. The objective of this study is to report a very rare case of spinal metastases of thymic carcinoma successfully operated by combination of instrumentation and cement augmentation together with adjuvant treatment. The management of these unique cases has yet to be well-documented.

PATIENT CONCERNS

A 57-year-old man presented with a 6-month history of continuous and progressive back pain. The patient, who had been diagnosed of thymic carcinoma (stage IV B) for 3 years, received surgical treatment of median sternotomy thymectomy, followed by 3 cycles of chemotherapy and 12 cycles of radiotherapy.

DIAGNOSIS

Magnetic resonance imaging (MRI) of spine showed spinal cord compression secondary to the epidural component of the T4 mass, with increased metastatic marrow infiltration of the left T4 vetebral body, which presented as a solid tumor. Post-operative pathology confirmed the diagnosis of spinal metastases of thymic carcinoma.

INTERVENTIONS

The patient underwent exploratory surgery, circumferential spinal cord decompression, cement augmentation and a stabilization procedure via a posterior approach.

OUTCOMES

The patient's neurological deficits improved significantly after the surgery, and the postoperative period was uneventful at the 3-month follow-up visit. There were no other complications associated with the operation during the follow-up period.

LESSONS

Taken together, the lesion's clinical features, imaging results, and pathological characteristics are unique. Combined efforts of specialists from orthopedics, neurosurgery, thoracic surgery, and medical oncology led to the successful diagnosis and management of this patient. Metastatic thymic carcinoma of the spine, although rare, should be part of the differential diagnosis when the patient has a history of thymic carcinoma and presents with back pain and radiculopathy. We recommend the posterior approach for spinal decompression of the metastatic thymic carcinoma when the tumor has caused neurological deficits. Osteoplasty by cement augmentation is also a good choice for surgical treatment.

Successful treatment of malignant thymoma with sacrum metastases: A case report and review of literature

RATIONALE

Malignant thymoma in the spine is a rare disease without standard curative managements so far. The objective of this article is to report a very rare case of recurrent malignant thymoma with sacrum metastases causing severe lumbosacral pain, which was presented with acute radiculopathy and treated with 2 operations combined with stabilization and cement augmentation. The management of these unique cases is not well-documented.

PATIENT CONCERNS

A 75-year-old man presented with lumbosacral pain, radiating pain and numbness of the left extremity. The patient underwent thymectomy in 2008, and posterior spinal cord decompression, tumor resection and a stabilization procedure in 2011. Pathologic results confirmed malignant thymomas of the spine. Imaging studies revealed the density of soft tissues, obvious bony destruction in the sacrum, and significant spinal cord obstruction.

DIAGNOSES

We believe this is a less-documented case of metastatic thymoma of the sacral spine presenting with back pain and radiculopathy, and presenting as a giant solid tumor.

INTERVENTIONS

The patient underwent osteoplasty via a posterior approach. Pathologic results confirmed malignant thymomas of the sacral spine.

OUTCOMES

The patient's neurological deficits improved significantly after the surgery, and the postoperative period was uneventful at the 6-month and 1-year follow-up visit. There were no other complications associated with the operation during the follow-up period.

LESSONS

This article emphasizes metastatic thymoma of the spine, although rare, should be part of the differential when the patient presents with back pain and radiculopathy. We recommend the posterior approach for spinal decompression of the metastatic thymoma when the tumor has caused neurological deficits. Osteoplasty by cement augmentation is also a good choice for surgical treatment.

Malignant thymoma with metastasis associated with paraneoplastic myasthenia gravis

We describe a patient who initially presented with a mixed thymic tumor and developed myasthenia gravis 8 years following thymectomy with recurrence of metastatic disease. Metastasis to the pleura, mediastinum, and cervical spine was identified with a positron emission tomography scan when this patient presented with recurring pneumonias and atrial fibrillation. The presentation and diagnosis were clouded by multiple courses of prednisone and chemotherapy for respiratory complications and metastatic disease, respectively. Classical myasthenia gravis symptoms emerged when his prednisone was tapered. The delayed presentation of paraneoplastic disease and the rare metastatic site make this case particularly unusual.

Metastatic Malignant Thymoma to the Abdomen: A SEER Database Review and Assessment of Treatment Strategies

BACKGROUND

Thymoma is a neoplasm occurring in 0.15 of 100,000 persons/year. Abdominal metastases are rare. We report the incidence of malignant thymoma (MT) and suggest imaging and treatment options for cases of abdominal metastasis.

METHODS

A National Cancer Institute's Surveillance, Epidemiology and End Results database review was conducted to identify MT cases, followed by a literature review examining cases of metastases to the abdomen. Incidence rates were calculated, and symptoms, treatments, size and location of tumors, disease-free interval (DFI), and survival time were recorded.

RESULTS

From 1973 to 2008, a total of 1,588 MT cases were identified (45.4 cases/year), which were extrapolated to 2,724 over 60 years. Incidence has risen from 17 cases in 1973 to 90 cases in 2008, with a larger incidence in males than females (0.23 vs. 0.17 per 100,000). There were 25 cases of abdominal metastasis (0.92%), 13 of which were asymptomatic. There was a wide variety of DFI and survival noted amongst the case reports. Multiple treatment modalities were used.

CONCLUSIONS

The incidence of MT is on the rise with a male predominance. All patients should receive routine imaging to look for extrathoracic metastases as half will not have symptoms. All patients with abdominal metastases should be treated using a multimodal approach.

Thymic epithelial tumors and metastasis to the brain: a case series and systematic review

Background

Thymic epithelial tumors (TETs) rarely metastasize to the brain. Clinico-pathologic features of TET patients with brain metastasis are not well described.

Methods

TET patients referred for consultation or screening for clinical trials are included. Imaging to evaluate for brain metastases was performed when clinically indicated or if required for screening. Tumor tissue from brain metastases was obtained for analysis, when available. Clinical characteristics and survival was evaluated and a systematic review of the literature on brain metastases associated with TETs was performed.

Results

Fourteen TET patients with brain metastasis were identified. Median age at TET diagnosis was 53 years (range: 31-71 years). Twelve patients had thymic carcinoma and two patients had World Health Organization B3 thymoma. Median time from TET diagnosis to discovery of brain metastases was 2.5 years (range: 9 months-8.3 years). Eleven patients had extracranial, extrathoracic metastases during presentation with brain metastases. Three patients underwent surgery and radiation therapy, eight patients received radiation therapy alone, and one patient had surgery alone. One patient with thymoma died 11 months after diagnosis of brain metastases and another patient died but with unknown date of diagnosis of brain metastases. Among 12 patients with thymic carcinoma, 11 of whom had a known date of brain metastases diagnosis, the median potential follow-up is 35.8 months, and median overall survival (OS) from diagnosis of brain metastases is 13.1 months.

Conclusions

Although uncommon, patients with advanced thymic carcinoma can develop brain metastases. Appropriate imaging and aggressive treatment should be considered for these patients.

Thymoma metastatic to liver and pancreas: case report and review of the literature

A 71-year-old man presented with a thymic mass involving the superior vena cava. A mediastinoscopical biopsy initially suggested a diagnosis of type A thymoma. After neoadjuvant chemotherapy, the patient underwent en-bloc thymectomy and vascular resection for a pathology-confirmed type B3 thymoma involving the superior vena cava, the left brachiocephalic vein and the distal part of the right brachiocephalic vein. Adjuvant radiotherapy was administered. Two years after the primary surgery, abdominal computed tomography (CT) and whole body fluorodeoxyglucose (18-FDG) positron emission tomography (PET) scans showed a single hepatic lesion that was treated with wedge liver resection. Pathological examination confirmed metastatic type B3 thymoma. Almost 4 years later, abdominal CT and 18-FDG PET revealed a 2.9-cm solid mass involving the body of the pancreas. Distal pancreatectomy with lymph node dissection was performed. Pathological examination showed a pancreatic metastasis from a type B3 thymoma, without lymph node involvement. The patient is alive and free of disease 6 months after the pancreatectomy (68 months after the initial thymectomy surgery). Intra-abdominal recurrence and pancreatic metastases are very uncommon manifestations of thymoma, but this event should be kept in mind when an abdominal mass is seen during follow-up.

Hepatic metastasis of thymoma: case report and immunohistochemical study

Thymomas are rare tumours characterised by their slow growth and capacity to invade directly by contiguity. While distant dissemination is infrequent, all sub-types of thymoma have the capacity to metastasise to extrathoracic organs. We present here the case of a female patient with a liver mass discovered 13 years after the removal of a mediastinal thymoma and after ten years from thyroidectomy for papillary carcinoma. The histopathological study showed that the lesion contained an epithelial component, which was immunohistochemically positive for pankeratin. It was accompanied by numerous small lymphocytes testing positive for TdT, CD3, CD4, CD5, CD8, CD99, and CD43. The result was consistent with hepatic metastatic thymoma sub-type B1, according to the World Health Organisation classification (WHO). Our case highlights the importance of morphological and immunohistological examinations in the differential diagnosis of visceral masses in patients with a history of thymoma. Given the infrequency of its metastasis and the increased risk of developing other primary tumours that these patients have, these studies play a significant role.

A Rare Tumor with a Very Rare Initial Presentation: Thymic Carcinoma as Bone Marrow Metastasis

Tumors of thymus gland are rare and account for 0.2% to 1.5% of all the neoplasms. They constitute a heterogeneous group that has an unknown etiology and a complex as well as varied biology. This has led to difficulty in their histological classification and in predicting their prognostic and survival markers. Among them, thymic carcinoma is the most aggressive thymic epithelial tumor exhibiting cytological malignant features and a diversity of clinicopathological characteristics that can cause diagnostic dilemmas, misdiagnosis, and therapeutic challenge. We herein describe a case of a 60-year-old man who while undergoing evaluation for the cause of pancytopenia was discovered having bone marrow metastasis from an asymptomatic thymic carcinoma. Bone marrow metastasis is an extremely rare initial presentation of thymic carcinoma with only few cases reported in the literature.

Thymoma Metastasis to the Semimembranosus Muscle

Thymoma is the most common thymic epithelial tumor whose classification was first introduced in 1999. Type B2 thymoma is considered a moderate/high-risk tumor; however, extrathoracic metastases are extremely rare with limited reports to date. In this report, we present a rare thymoma metastasis to the semimembranosus muscle, which was resected with a wide margin after confirmation by open biopsy. At the final follow-up after 1 year, no local recurrence has been observed.

[Thymic carcinomas]

Thymic carcinomas (TC) are approximately 10 times less prevalent than thymomas but of high clinical relevance because they are more aggressive, less frequently resectable than thymomas and usually refractory to classical and targeted long-term treatment approaches. Furthermore, in children and adolescents TC are more frequent than thymomas and particularly in this age group, germ cell tumors need to be a differential diagnostic consideration. In diagnostic terms pathologists face two challenges: a), the distinction between thymic carcinomas and thymomas with a similar appearance and b), the distinction between TC and histologically similar metastases and tumor extensions from other primary tumors. Overcoming these diagnostic challenges is the focus of the new WHO classification of thymic epithelial tumors. The objectives of this review are to highlight novel aspects of the WHO classification of thymic carcinomas and to address therapeutically relevant diagnostic pitfalls.

Metastatic Thymic Carcinoma Presenting as a Posterior Fossa Mass: Case Report and Review of the Literature

BACKGROUND

Thymic epithelial tumors (TETs) are uncommon lesions, and cerebral metastases from these tumors are even rarer. We report a case of a posterior fossa metastasis in a patient with a known history of thymic carcinoma.

CASE DESCRIPTION

A 47-year-old man with a history of Hodgkin lymphoma and thymic carcinoma presented with headache, nausea, and ataxia. Imaging revealed a large posterior fossa mass. This lesion was completely resected without complications. Pathologic examination was consistent with metastatic thymic carcinoma. The patient's symptoms were relieved postoperatively. We reviewed the literature and identified an additional 44 cases of TETs with metastases to the brain. Although brain metastases are generally associated with a poor prognosis in patients with TETs, survival of more than 1 year may be accomplished with surgical resection and multimodality treatment.

CONCLUSIONS

Metastasis should be considered in the differential of a patient with a TET and an intracranial mass lesion.

A large microRNA cluster on chromosome 19 is a transcriptional hallmark of WHO type A and AB thymomas

Background:

Thymomas are one of the most rarely diagnosed malignancies. To better understand its biology and to identify therapeutic targets, we performed next-generation RNA sequencing.

Methods:

The RNA was sequenced from 13 thymic malignancies and 3 normal thymus glands. Validation of microRNA expression was performed on a separate set of 35 thymic malignancies. For cell-based studies, a thymoma cell line was used.

Results:

Hierarchical clustering revealed 100% concordance between gene expression clusters and WHO subtype. A substantial differentiator was a large microRNA cluster on chr19q13.42 that was significantly overexpressed in all A and AB tumours and whose expression was virtually absent in the other thymomas and normal tissues. Overexpression of this microRNA cluster activates the PI3K/AKT/mTOR pathway. Treatment of a thymoma AB cell line with a panel of PI3K/AKT/mTOR inhibitors resulted in marked reduction of cell viability.

Conclusions:

A large microRNA cluster on chr19q13.42 is a transcriptional hallmark of type A and AB thymomas. Furthermore, this cluster activates the PI3K pathway, suggesting the possible exploration of PI3K inhibitors in patients with these subtypes of tumour. This work has led to the initiation of a phase II clinical trial of PI3K inhibition in relapsed or refractory thymomas (http://clinicaltrials.gov/ct2/show/NCT02220855).

FDG PET/CT Manifestation of Rare Widespread Metastatic Chemoradiation-Refractory Thymic Squamous Cell Carcinoma

A 74-year-old man underwent excisional biopsy of an anterior mediastinal mass that revealed squamous cell carcinoma of thymic origin. Immunohistochemistry revealed insulin-like growth factor-1 receptor positivity, which has been associated with worse prognosis. Restaging FDG PET/CT revealed extensive soft tissue and osseous metastases despite surgery and chemoradiation therapy. Patient was then enrolled in a clinical trial with anti-insulin-like growth factor-1 receptor therapy. A 3-month follow-up FDG PET/CT showed disease progression with an increase in size and number of hypermetabolic metastatic lesions, including interval development of multiple new metastases.

Ovarian Metastasis of a Thymoma: Report of a Case and Literature Review

Thymomas are infrequent, although they are the most common neoplasms in the anterior mediastinum. They are slow-growing tumors that may involve surrounding structures by direct extension. In these aggressive cases, intrathoracic recurrences are frequent. However, distant metastases are uncommon, the most common sites including liver, lymph nodes, and bones. Metastatic thymoma to the ovary is exceedingly rare, with only 6 cases reported in the literature. We report a 46-yr-old female with a metastatic thymoma to her left ovary 6 yr after the initial diagnosis of thymoma, Type B1 with pleural invasion.

Type A and AB thymomas: histological features associated with increased stage

AIMS

The current WHO classification of thymic epithelial neoplasms describes type A and type AB thymomas as behaving 'like benign neoplasms'. However, recent published data suggest that rare cases may show more aggressive behaviour. The aim of this study was to assess the frequency of atypical cases, and to determine whether atypia is associated with more advanced disease.

METHODS AND RESULTS

One hundred and twenty-one thymomas (type A, n = 68; type AB, n = 53) were retrospectively reviewed for 'atypical' features (nuclear pleomorphism, mitotic activity, and necrosis). Logistic regression was used to ascertain the association with increasing Masaoka-Koga stage. Where available, follow-up data were also reviewed. There were 72 stage I, 42 stage II, five stage III and two stage IV tumours. Only the presence of necrosis showed a significant association with increased stage in univariate and multivariate analysis. Nuclear atypia and increased mitotic activity were not associated with increasing stage of disease.

CONCLUSIONS

Our data support the concept of there being more aggressive atypical variants of both type A and type AB thymoma, and suggest that the presence of necrosis could be used to predict aggressive behaviour.

Spinal metastasis of thymic carcinoma as a rare manifestation: a summary of 7 consecutive cases

BACKGROUNDS

Thymic carcinomas are very rare tumors that are often associated with extrathoracic metastasis to other organs. However, it is well known that thymic carcinomas rarely metastasize to the spine, and the prognosis, treatment, and natural course of this disease are not yet standardized.

METHODS

We describe seven thymic carcinoma patients with spinal metastasis who were diagnosed and treated in our institute from January 2006 to December 2011. We performed surgical treatment and adjuvant chemotherapy and/or radiation therapy, in consideration of each individual disease's course, and we regularly followed up the patients.

RESULTS

Of the seven patients, five were male and two were female. Six had metastases in the thoracic spine, and one had metastases in the lumbar spine. An extradural lesion was found in five patients, and two patients had both extradural and intradural lesions. The period from the primary diagnosis to spinal metastases varied widely (range, 1.23-14 years). After surgery, all patients showed an improvement of back pain and radicular pain. Two patients were lost to follow-up, but the other five maintained ambulatory function until their final follow-up. Four patients died because of pulmonary complications accompanied with the disease's progression. One patient died from uncontrolled brain metastases. After surgery, the median survival was 204±111.43 days.

CONCLUSION

Because metastasis to the spine from thymic carcinoma is very rare, there are no treatment guidelines. Nevertheless, we suggest that appropriate surgical management of the metastatic lesion is necessary for the preservation of the patient's quality of life during survival.

Asymptomatic pelvic metastasis from thymic carcinoma: a case report

Thymic epithelial tumors are rare and often occur somewhere local. Metastatic sites of thymic carcinomas (Masaoka-Koga stage IVb) are mostly seen in the lung, liver and brain. We report a 64-year-old female with an initial diagnosis of thymoma B3 who first showed thoracic recurrences and then an asymptomatic isolated pelvic metastasis from her thymic carcinoma.

Diagnostic features and subtyping of thymoma lymph node metastases

Aim. The purpose of the present study was to characterize the morphological features of thymoma metastases in lymph nodes and to evaluate the possibility of their subtyping according to the 2004 WHO classification of thymus tumors. Materials and Methods. We reviewed 210 thymoma cases in our series of thymic epithelial tumors (TET), including their recurrences and lymphogenous metastases. Three cases of lymph node metastases, one case occurring synchronously with the primary tumor and one synchronously with the first relapse (both in intrathoracic location) and one case of metastasis observed in a laterocervical lymph node subsequently to two thymoma relapses were found. Results. The metastatic nodes were variably but extensively involved in all cases. The histological features were similar in both primary tumors and metastases. Thymoma metastases were subtyped according to the WHO classification as B3 (one case) and B2 (two cases), and distinctive features in comparison to metastatic epithelial neoplasias from other sites were observed. Conclusion. Thymoma lymph node metastases, although rare, can be subtyped according to the WHO classification on the basis of their morphological and immunohistochemical features. Clinically, the presence of nodal metastases may herald subsequent relapses and further metastases even in extrathoracic sites.

The prognostic value of architectural patterns in a study of 37 type AB thymomas

Spindle cell thymomas with prominent amount of lymphocytes are classified as WHO type AB tumors. However, there are architectural pattern differences in these tumors. We investigated the importance of architectural pattern in type AB thymomas in relation to prognostic value. Archival hematoxylin-eosin stained slides of 37 AB type thymomas were reviewed for the presence (type 1) or absence (type 2) of reticular growth pattern. Reticular growth pattern is defined as the presence of a network of elongated bland spindle cells separating nests of tumor cells admixed with lymphoid cells. The architectural patterns were correlated with tumor stage at diagnosis and presence or absence of recurrent disease. The analysis identified 18 cases of type 1 AB thymoma and 19 cases of type 2. Type 2 cases also had greater cytologic atypia within the spindle cells. Patients with type 1 tumors were more likely to have early stage disease. In contrast, type 2 pattern was associated with higher stage at diagnosis (P<0.001) and greater likelihood for recurrence (P<0.05) and metastases. Architectural features are prognostically relevant in classification of WHO AB type thymomas and may constitute a form of personalized medicine. Independent confirmation of the findings is necessary to confirm the association of architectural pattern with outcomes.

Metastasis to the kidney from a B2 thymoma: report of a case

Thymomas are tumors with an indolent behavior and long clinical course, usually confined to the anterior mediastinum. Local recurrence is frequent while distant metastases are extremely rare. We report an unusual case of a B2 thymoma with a single renal metastasis The challenge in this case was the frozen section intraoperative diagnosis because of the clinical suspicion of malignant lymphoma. This report also highlights the role of surgical removal of solitary metastases.

The role of histology in predicting recurrence of type A thymomas: a clinicopathologic correlation of 23 cases

Spindle cell thymomas (type A), as per the WHO definition, are benign tumors with an excellent prognosis. However, recent studies document aggressive behavior with local recurrences as well as extrathoracic metastases. More recently, Nonaka and Rosai have raised the question as to whether atypical features like cellular atypia, mitotic activity, necrosis, and vascular permeation could predict the adverse outcomes of these tumors. In an effort to address the 'atypia and outcome' issue of spindle cell thymomas, we analyzed our database of over 600 cases of thymic tumors to identify type A thymomas. The presence of histomorphological features like tumor size, nuclear shape and variability, mitotic rate, and presence/absence of necrosis were correlated with Masaoka stage, relapse/recurrence, and extrathoracic metastases. The study identified 23 patients of pure spindle cell thymomas (WHO type A) ranging in age from 40 to 88 years (median age, 54 years) and with male-to-female ratio of 1:0.9. Approximately 43% of the cases had recurrence or metastases during the followup period (average, 49 months). The presence of necrosis correlates with both relapse and extrathoracic metastases but not with the stage of diagnosis. However, none of the other clinical or histological features, including size, predominant nuclear shape, nuclear variability, and mitotic activity, were correlated with the outcome parameters, such as stage at diagnosis, presence or absence of relapse, and extrathoracic metastases. Histological atypia is fairly common in WHO type A thymomas. The presence of necrosis was associated with both locoregional and systemic disease. However, none of the other clinical or histological features correlated with aggressive behavior.

A gene signature to determine metastatic behavior in thymomas

Purpose

Thymoma represents one of the rarest of all malignancies. Stage and completeness of resection have been used to ascertain postoperative therapeutic strategies albeit with limited prognostic accuracy. A molecular classifier would be useful to improve the assessment of metastatic behaviour and optimize patient management.

Methods

qRT-PCR assay for 23 genes (19 test and four reference genes) was performed on multi-institutional archival primary thymomas (n = 36). Gene expression levels were used to compute a signature, classifying tumors into classes 1 and 2, corresponding to low or high likelihood for metastases. The signature was validated in an independent multi-institutional cohort of patients (n = 75).

Results

A nine-gene signature that can predict metastatic behavior of thymomas was developed and validated. Using radial basis machine modeling in the training set, 5-year and 10-year metastasis-free survival rates were 77% and 26% for predicted low (class 1) and high (class 2) risk of metastasis (P = 0.0047, log-rank), respectively. For the validation set, 5-year metastasis-free survival rates were 97% and 30% for predicted low- and high-risk patients (P = 0.0004, log-rank), respectively. The 5-year metastasis-free survival rates for the validation set were 49% and 41% for Masaoka stages I/II and III/IV (P = 0.0537, log-rank), respectively. In univariate and multivariate Cox models evaluating common prognostic factors for thymoma metastasis, the nine-gene signature was the only independent indicator of metastases (P = 0.036).

Conclusion

A nine-gene signature was established and validated which predicts the likelihood of metastasis more accurately than traditional staging. This further underscores the biologic determinants of the clinical course of thymoma and may improve patient management.

Establishment and characterization of a novel cell line derived from human thymoma AB tumor

Thymomas are low-grade epithelial tumors of the anterior mediastinum. The complexity of the disease and the lack of in vitro and in vivo models hamper the development of better therapeutics. In this study, we report a novel cell line, designated as IU-TAB-1, which was established from a patient with stage II thymoma (World Health Organization-type AB). The IU-TAB-1 cell line was established in vitro and characterized using histological and immunohistochemical staining, fluorescence-activated cell sorting, cytogenetic analyses and functional assays including in vitro and a NOD/SCID xenograft model. A whole-genome gene expression analysis (Illumina) was performed on the IU-TAB-1 cell line and 34 thymomas to determine the clinical relevance of the cell line. The IU-TAB-1 cell line was positive for epithelial markers (pan-cytokeratin and EpCAM/CD326) including thymic epithelial (TE) surface markers (such as CD29, CD9, CD54/ICAM-1, CD58 and CD24) and p63, and negative for B- and T-cell lineage markers. Gene expression profiling demonstrated overlapping and distinct genes between IU-TAB-1 and primary thymomas including the primary tumor (from which the cell line was derived). IU-TAB-1 cells are tumorigenic when implanted in immunodeficient mice with tumors reaching a volume of 1000 mm³ at around 130 days. The established cell line represents a biologically relevant new tool to investigate the molecular pathology of thymic malignancies and to evaluate the efficacy of novel therapeutics both in vitro and in vivo.