Thymic Carcinoma: Current Concepts and Histologic Features

Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways

BACKGROUND

Thymic carcinomas (TCs) and thymic neuroendocrine neoplasms (TNENs) are two aggressive subtypes of thymic malignancy. Traditional therapy for advanced TCs and TNENs has limited outcome. New genomic profiling of TCs and TNENs might provide insights that contribute to the development of new treatment approaches.

METHODS

We used gene panel sequencing technologies to investigate the genetic aberrations of 32 TC patients and 15 TNEN patients who underwent surgery at Shanghai Chest Hospital between 2015 and 2017. Patient samples were sequenced using a 324-gene platform with licensed technologies. In this study, we focused on clinically relevant genomic alterations (CRGAs), which are previously proven to be pathogenic alterations, to identify the pathology-specific mutational patterns, prognostic signatures of TCs and TNENs.

RESULTS

The mutational profiles between TCs and TNENs were diverse. The genetic alterations that ranked highest in TCs were in CDKN2A, TP53, ASXL1, CDKN2B, PIK3C2G, PTCH1, and ROS1 , while those in TNENs were in MEN1, MLL2, APC, RB1 , and TSC2 . Prognostic analysis showed that mutations of ROS1, CDKN2A, CDKN2B, BRAF, and BAP1 were significantly associated with worse outcomes in TC patients, and that mutation of ERBB2 indicated shortened disease-free survival (DFS) and overall survival (OS) in TNEN patients. Further investigation found that the prognosis-related genes were focused on signal pathways of cell cycle control, chromatin remodeling/DNA methylation, phosphoinositide 3-kinases (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR), and receptor tyrosine kinase (RTK)/RAS/mitogen-activated protein kinase (MAPK) signaling.

CONCLUSION

We profiled the mutational features of 47 Chinese patients with thymic malignancy of diverse pathologic phenotypes to uncover the integrated genomic landscape of these rare tumors, and identified the pathology-specific mutational patterns, prognostic signatures, and potential therapeutic targets for TCs and TNENs.

Chromophobe-like carcinoma of the thymus: A clinicopathological and immunohistochemical correlation of 5 cases

Five cases of primary thymic carcinoma with distinct histopathological features resembling chromophobe carcinomas are presented. The patients were four men and one woman ranging in age between 43 and 72 years. Clinically, the patients presented with non-specific symptoms of dyspnea and chest pain. Diagnostic imaging revealed the presence of anterior mediastinal masses. All patients underwent complete surgical resection of their tumors via thoracotomy. Grossly, the tumors measured between 4.0 and 5.5 cm in greatest diameter and were ill-defined neoplasms with infiltrative borders; they were light brown in color and had a lobulated surface. Areas of hemorrhage and necrosis were not identified. Histologically, all tumors shared similar histopathological features, mainly the presence of infiltrative tumor islands separated by a fibrocollagenous stroma. At higher magnification, the neoplastic cellular proliferation was composed of medium-sized, round to polygonal cells with eosinophilic or granular cytoplasm and a clear perinuclear cytoplasmic halo, which imparted a chromophobe-like appearance. Nuclear atypia and mitotic activity were identified. Histochemical stains for colloidal iron were negative while immunohistochemical stains for pancytokeratin, cytokeratin 5/6, and p40 were positive in all cases, supporting squamous differentiation in these tumors. Clinical follow-up information was obtained in three patients all of whom died between 3 and 5 years after initial diagnosis, while two patients were lost to follow-up. The cellular characteristics of these tumors represent an unusual variant of thymic carcinoma that may pose a diagnostic challenge in small biopsies and that could be easily confused with other primary or metastatic tumors.

Ectopic Thymic Carcinoma Located on The Dorsal Side of The Thyroid Gland

Migration of the embryonic thymus is thought to be the basis for the formation of ectopic thymic tumors. Thymic ectopy may be a result of the abnormal migration of the third or fourth branchial cleft to the anterior mediastinum during weeks 5–6 of embryonic development. However, ectopic thymic carcinoma has highly nonspecific histologic features and occurs in variable and unpredictable locations making it difficult to diagnose. However, the clinical diagnosis and treatment should not overlook the possibility of ectopic thymic tumors. Here, we report a case of ectopic thymic carcinoma diagnosed as thyroid cancer before surgery occurring in a location consistent with current assumptions. Furthermore, we briefly review the literature on ectopic thymic carcinoma and discuss current diagnostic and treatment approaches.

Desmoplastic Adamantinoma-like Thymic Carcinoma: Clinicopathologic, Immunohistochemical, and Molecular Study of 5 Cases

Five cases of a heretofore unreported rare variant of thymic carcinoma characterized by a striking resemblance to adamantinoma of the mandible are described. The tumors occurred in 4 women and 1 man aged 58 to 76 years (mean: 67.8 y); they arose in the anterior mediastinum and measured from 5.3 to 12.0 cm in greatest diameter (mean: 8.9 cm). Presenting symptoms included chest pain, shortness of breath, and in 2 patients, pleural effusion. One tumor was asymptomatic and discovered incidentally. Histologically, the tumors were extensively desmoplastic, and the cellular proliferation was characterized by multiple islands of squamous epithelium with striking peripheral palisading of nuclei and central areas containing clear cells resembling a stellate reticulum. Areas of preexisting spindle cell thymoma were identified in 2 cases; these areas gradually merged with the higher-grade component of the lesion. Cystic changes were noted in 3 cases. Immunohistochemical studies in 3 cases showed the tumor cells were positive for cytokeratins, p40 and p63, and all showed a high proliferation rate (>50% nuclear positivity) with Ki-67. Next-generation sequencing was performed in 2 cases that showed amplification of the AKT1 gene (copy numbers 6 and 13). Clinical follow-up in 3 patients showed recurrence and metastasis after 1 and 2 years; 1 patient passed away 2 years after diagnosis due to the tumor. Desmoplastic adamantinoma-like thymic carcinoma represents an unusual histologic variant of thymic carcinoma that needs to be distinguished from metastases from similar tumors to the mediastinum.

Thymic Carcinoma: A Review

The diagnosis of thymic carcinoma may pose significant problems not necessarily in the histopathological diagnosis but rather in assigning the thymus as specific origin. Often the tissue available for interpretation is obtained via a mediastinocopic biopsy, which raises two different issues -minimal tissue and lack of specific features to make a carcinoma of thymic origin. In addition, if to that conundrum we add that there is no magic immunohistochemical stain that will unequivocally lead to the interpretation of thymic carcinoma, then we are left with a true clinical-radiological-pathological correlation. In this review, we will highlight some of those challenges that diagnostic surgical pathologists may encounter in the histopathological assessment of thymic carcinoma as well as in the staging of these tumors.

A spontaneous thymic carcinosarcoma in a young Sprague Dawley rat

We encountered a case of spontaneous thymic carcinosarcoma in a young Crl:CD (Sprague Dawley) rat. Grossly, a white multinodular mass replaced the thymus in the thoracic cavity. Histologically, multiple nodules were separated by fibrous stroma, and each nodule included isolated regions that were composed of epithelial or non-epithelial tumor cells. The epithelial tumor cells were relatively large and round to polygonal cells with large nuclei and weakly eosinophilic cytoplasm. These cells were cytokeratin-positive and vimentin-negative. These cells infiltrated the lungs. The non-epithelial tumor cells were poorly differentiated, small, round to spindle-shaped cells with small nuclei and basophilic cytoplasm. These cells were vimentin-positive and mostly cytokeratin-negative. Many islands of cartilage were observed near non-epithelial cells. Based on these findings, the tumor was diagnosed as a primary thymic carcinosarcoma consisting of a malignant thymoma composed of epithelial tumor cells and a mesenchymal chondrosarcoma composed of non-epithelial tumor cells.

Clear Cell Carcinoma of the Thymus: An Improbable Enemy

Introduction

Thymic clear cell carcinoma is the most uncommon subtype of thymic carcinoma, with 20 cases reported worldwide.

Case description

We present the case of a 61-year-old female with dyspnoea and chest pain for 2 days. Computed tomography (CT) angiography showed pulmonary thromboembolism and the existence of mediastinal and bilateral hilar lymphadenopathy, the largest infracarinal with an inferior axis of 25 mm, and also, micronodules on the left pulmonary parenchyma. The patient was admitted for aetiological assessment and underwent anticoagulant therapy. After a month, she had an ischaemic stroke, the sequelae of which proved to be fatal. The autopsy showed a mass in the superior-anterior mediastinum, with dimensions of 11×8×6 cm, corresponding to a thymus signet ring cell primary carcinoma. The immunohistochemistry study revealed that this mass was positive for AE1/AE3, CK5/6 and CK7.

Conclusion

The clinical, morphological and immunophenotypic diversity of this tumour makes its diagnosis a difficult multidisciplinary challenge, which requires a high level of clinical knowledge and accurate imaging and histological investigation.

LEARNING POINTS

Thymic clear cell carcinoma is a very rare entity with an aggressive and nonspecific clinical behaviour.There are no defined diagnostic criteria, although diagnosis could be established with histologic/cytology analysis.There are no clear guidelines for treatment, which can include highly invasive surgery and chemotherapy or radiation therapy.

Pathological and clinical features of enteric adenocarcinoma of the thymus. A pooled analysis of cases from a reference center and systematic review of the literature

BACKGROUND

Primary enteric adenocarcinoma of the thymus (EAT) is a recently proposed rare subtype of thymic carcinoma. Unlike thymic carcinomas with squamous histology, for which clinical guidelines are available, little knowledge is available regarding the clinical and pathological features of EAT, and there is no consensus on the best treatment algorithm for such tumors.

METHODS

We performed a systematic review of the literature, searching for all cases of EAT reported. We also retrospectively reviewed all cases of EAT treated at the European Institute of Oncology (IEO) between January 2000 and January 2020. Individual patient data were extracted and analyzed in order to delineate clinical and pathological features, as well as patients' prognosis and treatments outcome, evaluated in terms of Disease free Survival (DFS), Progression free survival (PFS) and overall survival (OS).

RESULTS

Thirty-three cases (29 reported in literature and 4 new cases treated at IEO) of thymic adenocarcinoma deploying enteric differentiation as defined by WHO-criteria were analyzed. All tumors showed positive immunoreactivity for cytokeratin (CK) 20 and/or caudal type homeobox 2 (CDX2). Data on molecular profiling by next-generation sequencing were available in only 3 cases, and did not show actionable findings. At diagnosis, 11 pts had an early-stage (Masaoka I-II) and 22 a locally advanced (10 pts) or metastatic (12 pts) disease. Median-DFS of patients with localized disease was 12 months (95% CI, 7-19). Patients who received systemic chemotherapy were mostly treated with regimens commonly used for thymic epithelial tumors, with a discouraging PFS of 3-5 months for patients with stage IV disease. Median OS of the whole population was 34 months (95% CI, 24-NA:. mOS was not reached for patients with stage I-II disease versus 34 months in stage III-IV (p < 0.05).

CONCLUSION

Available evidence suggests that EAT represents a distinct entity in the context of thymic epithelial tumors, characterized by aggressive clinical behavior, poor responsiveness to chemotherapy and dismal patients prognosis. More research is needed to better define optimal management strategies for patients with such rare disease.

The role of needle core biopsies in the evaluation of thymic epithelial neoplasms

Thymic epithelial neoplasms are rare tumors derived from thymic epithelium that most often present as large anterior mediastinal masses. The vast majority of thymic epithelial neoplasms fall under the diagnostic category of thymoma, with a smaller percentage qualifying for a diagnosis of thymic carcinoma. The ability to render a definitive diagnosis on these tumors is generally hampered by their deep location and close proximity to vital structures, which makes biopsy sampling for histopathologic evaluation difficult. In recent years, the trend in medicine has been to opt for the least invasive procedure to obtain tissue samples that, by definition, implies also obtaining smaller and smaller biopsies, resulting in lesser amounts of tissue available for examination. In the mediastinum, the most common modalities for procuring biopsy samples from mass lesions include fine-needle aspiration, percutaneous core needle biopsy and video-assisted thoracoscopic biopsy. In this review, we will deal only with the role and limitations of percutaneous core biopsies in the interpretation of thymic epithelial neoplasms.

Deciphering tissue-based proteome signatures revealed novel subtyping and prognostic markers for thymic epithelial tumors

Thymic epithelial tumors (TETs) belong to a group of tumors that rarely occur, but have unresolved mechanisms and heterogeneous clinical behaviors. Current care of TET patients demands biomarkers of high sensitivity and specificity for accurate histological classification and prognosis management. In this study, 134 fresh‐frozen tissue samples (84 tumor, 40 tumor adjacent, and 10 normal thymus) were recruited to generate a quantitative and systematic view of proteomic landscape of TETs. Among them, 90 samples were analyzed by data‐independent acquisition mass spectrometry (DIA‐MS) leading to discovery of novel classifying molecules among different TET subtypes. The correlation between clinical outcome and the identified molecules was probed, and the prioritized proteins of interest were further validated on the remaining samples (n = 44) via parallel reaction monitoring (PRM) as well as immunohistochemical and confocal imaging analysis. In particular, two proteins, the cellular mRNA deadenylase CCR4 (carbon catabolite repressor 4)‐NOT (negative on TATA) complex subunit 2/9 (CNOT2/9) and the serine hydroxymethyltransferase that catalyzes the reversible interconversions of serine and glycine (SHMT1), were found at dramatic low levels in the thymic epithelia of more malignant subtype, thymic squamous cell carcinoma (TSCC). Interestingly, the mRNA levels of these two genes were shown to be closely correlated with prognosis of the TET patients. These results extended the existing human tissue proteome atlas and allowed us to identify several new protein classifiers for TET subtyping. Newly identified subtyping and prognosis markers, CNOT2/9 and SHMT1, will expand current diagnostic arsenal in terms of higher specificity and prognostic insights for TET diagnosis and management.

Cystic and Encapsulated Atypical Thymoma (World Health Organization Type B3)

OBJECTIVES

Eight cases of encapsulated and cystic atypical thymomas (World Health Organization type B3) are presented.

METHODS

Cases were identified after review of more than 500 thymomas. Histologic material from surgical resections was evaluated.

RESULTS

The patients are seven men and one woman aged 43 to 71 years. Seven patients presented with nonspecific symptoms while one mass was found on autopsy. The tumors were 4 to 6 cm in greatest dimension and showed prominent cystic changes with an epithelial proliferation arranged in sheets and cords. Increased mitotic activity and nuclear pleomorphism were not identified. All tumors were encapsulated. Immunohistochemical studies showed the tumor cells positive for keratin cocktail, keratin 5/6, and p63. Clinical follow-up was available in five patients. All were alive without recurrence.

CONCLUSIONS

These cases represent an unusual variant of atypical thymoma that can be misdiagnosed as thymic carcinoma or multilocular thymic cyst. Awareness of this histologic growth pattern is important for accurate diagnosis.

Primary clear cell carcinoma of the thymus and literature comparison of features

Clear cell carcinoma arising from the thymus is considered exceedingly rare. It shows aggressive clinical behavior and demonstrates frequent local recurrences as well as widespread metastasis. The detailed clinical data of one patient with thymic clear cell carcinoma were compiled, and a review of relevant reported studies was performed. We summarized the clinical characteristics, pathological diagnosis of the patient and other reported cases. The analysis showed that older male patients were more likely to suffer, and the manifestations included chest pain and dyspnea. Some patients are asymptomatic, with the tumor being discovered during physical examination. Histologically, thymic clear cell carcinoma is composed of lobulated structures arranged in hyperchromatic fibrous stroma; the tumor cells are uniform with obvious nucleoli and clear cytoplasm. To establish the correct diagnosis, consideration and exclusion of metastasis and other original tumors in the differential diagnosis by immunohistochemistry, clinical and radiologic correlation is important.

Epidural Metastasis in Malignant Thymoma Mimicking Epidural Abscess: Case Report and Literature Review

Thymoma and thymic carcinoma are rare epithelial tumors that originate from the thymus gland. Extrathoracic metastases occur in the liver, kidney, and bone in 1% to 15% of patients. Although thymoma and thymic carcinoma exhibit highly aggressive biological behavior, spinal metastasis is rare. We describe a 78-year-old man with left wrist and grasp weakness that occurred 7 days before admission. The patient underwent thymoma surgery 7 years ago and was cured. Magnetic resonance images showed a rim-enhanced mass in the C6-7-T1 epidural space. C6-7-T1 laminectomy was performed and the mass was removed. Histological examination was performed and patient was diagnosed with metastatic thymoma. The previous reported case occurred with involvement of the vertebral body or posterior element, but our case was mostly rim-enhanced and appeared as an abscess and intradural extramedullary tumor.

Thymic carcinoma initially presented with geographic destruction of scapula in a child

As the conventional histopathologic examination of thymic carcinoma (TC) is nonspecific, immunohistochemical studies along with correlative radiographic investigations are needed for its correct diagnosis. TC commonly occurs in the late 5th to early 6th decades of life but is extremely rare in childhood. It may be incidentally detected from chest radiographs taken as routine or for other reasons. However, most patients present with symptoms such as chest pain, cough, shortness of breath, dysphagia and hoarseness, which are directly attributable to the mediastinal mass. Although TC frequently invades the neighboring organs, pleura and pericardium and metastasizes to the lymph nodes, liver and lung at the time of the first diagnosis, initial or late metastasis to the bone has been seldom reported in adults. Indeed, the English literature revealed no earlier report on initial bony metastasis in a child to date. We report a case of TC in a 12-year-old boy who initially presented with scapular osteolysis masquerading as a primary bone tumor to emphasize the usefulness of combined imaging for staging and histologic studies, particularly for such an unexpected case.

The enlightenments from ITMIG Consensus on WHO histological classification of thymoma and thymic carcinoma: refined definitions, histological criteria, and reporting

The World Health Organization (WHO) histological classification of the thymoma and thymic carcinoma (TC) has been criticized for poor interobserver reproducibility or inconsistencies in the routine pathological diagnosis. The International Thymic Malignancy Interest Group (ITMIG) panel achieved an agreement to maintain the widely accepted WHO framework but to refine historic definitions and histological criteria, and further introduce some new terms with the aim to improve interobserver reproducibility. This review addresses the enlightenments we can get from the ITMIG consensus on the WHO histological classification of the thymoma and TC, which may be helpful for most pathologists.

Thymoma and thymic carcinomas

Thymomas (Ts) and thymic carcinomas (TCs) are rare tumours of the mediastinum with an incidence rate of 1.7/million per year in Europe. Histological classification is based on rate of non-malignant-appearing thymic epithelial cells and proportions of lymphocytes (A, AB, B1, B2, B3, and C), while staging system concerns localisation of the involved areas. Surgery is the mainstay of treatment with a 10-year survival of 80%, 78%, 75%, and 42% for stages I, II, III and IV, respectively, with an R0 resection. Radiotherapy has a role in selected cases (stage III patients or R1-2 residual) and platinum-based chemotherapy remains the standard of care for patients with advanced disease. A multimodality approach would be advisable when surgery is not recommended. Since molecular aberrations are poorly understood and few responses are reported, targeted therapies are yet being studied. In this review, we describe key aspects of clinical management for Ts and TCs.

Choroidal metastases from thymic carcinoma during pregnancy: Case Report

BACKGROUND

Rare sites of metastases, atypical symptoms and paraneoplastic syndromes are often neglected or misinterpreted, especially when they represent early symptoms of an underlying malignant disease. Hence, an interdisciplinary approach to these patients is essential to avoid tumor progression and metastatic spread in order to provide curative treatment options to the patients. We here report the case of a young woman presenting with visual loss which led to diagnosis of a thymic carcinoma.

CASE PRESENTATION

A 28-year old white woman presented with subacute loss of vision in the last trimester of her first pregnancy which was first interpreted as an exacerbation of a pre-existing dermatomyositis and treated with steroids. After failure of steroid therapy choroidal metastases from an undifferentiated thymic carcinoma were diagnosed. This also shed a new light on the dermatomyositis the patient had been suffering from for seven years possibly representing a paraneoplastic syndrome from the tumor. Despite aggressive chemotherapy, the patient died from progressive disease eight years after first onset of dermatomyositis and 14 months after initial diagnosis of the thymic carcinoma.

CONCLUSIONS

Choroidal metastases from a thymic carcinoma have never been reported before but should be included into the differential diagnosis of choroidal masses.

A rare case of primary thymic adenocarcinoma mimicking small cell lung cancer

Primary thymic adenocarcinoma is a very rare malignancy of the anterior mediastinum with no standardized treatment. A 36-year-old male patient presented with hoarseness over the past 3 months. A chest computed tomography (CT) scan showed an infiltrative mass to the proximal vessels and aortic arch in left upper mediastinum (4.1×3.1×5.4 cm). Brain magnetic resonance imaging (MRI) showed focal lesions, suggesting metastasis in the left frontal lobe. A thoracoscopic biopsy of the mediastinal mass confirmed a primary thymic adenocarcinoma forming a glandular structure with atypia of tumor cells. The patient received four cycles of systemic chemotherapy, consisting of etoposide and cisplatin, with concurrent radiotherapy (6,000 cGy/30 fractions) to the mediastinal lesion and the metastatic brain lesion (4,200 cGy/12 fractions). A follow-up chest CT scan and brain MRI showed a decrease in the size of the left upper mediastinal mass and brain lesion. We report a rare case of the primary thymic adenocarcinoma with a literature review.

ITMIG consensus statement on the use of the WHO histological classification of thymoma and thymic carcinoma: refined definitions, histological criteria, and reporting

INTRODUCTION

The 2004 version of the World Health Organization classification subdivides thymic epithelial tumors into A, AB, B1, B2, and B3 (and rare other) thymomas and thymic carcinomas (TC). Due to a morphological continuum between some thymoma subtypes and some morphological overlap between thymomas and TC, a variable proportion of cases may pose problems in classification, contributing to the poor interobserver reproducibility in some studies.

METHODS

To overcome this problem, hematoxylin-eosin-stained and immunohistochemically processed sections of prototypic, "borderland," and "combined" thymomas and TC (n = 72) were studied by 18 pathologists at an international consensus slide workshop supported by the International Thymic Malignancy Interest Group.

RESULTS

Consensus was achieved on refined criteria for decision making at the A/AB borderland, the distinction between B1, B2, and B3 thymomas and the separation of B3 thymomas from TCs. "Atypical type A thymoma" is tentatively proposed as a new type A thymoma variant. New reporting strategies for tumors with more than one histological pattern are proposed.

CONCLUSION

These guidelines can set the stage for reproducibility studies and the design of a clinically meaningful grading system for thymic epithelial tumors.

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.

Advances in thymic carcinoma diagnosis and treatment: a review of literature

Thymomas account for up to 50 % of anterior mediastinal neoplasms with an incidence of 0.13 per 100,000 person-years in the USA. Thymic carcinoma is a rare malignancy of the thymus gland distinguished from thymomas as it has a more invasive and metastasizing potential conferring poor prognosis. Due to the rarity of thymic carcinoma and the great variety of its histological subtypes, there is no solid evidence on optimal staging, imaging and treatment guidelines. Herein, we systematically review the literature on current clinical practice with regard to diagnostic evaluation, histopathological assessment, management and treatment of squamous thymic carcinoma.

Delayed distant spinal metastasis in thymomas

STUDY DESIGN

A case report.

OBJECTIVE

To demonstrate 2 cases of delayed distant spinal metastasis from a thymoma with comprehensive immunohisto-chemical analysis.

SUMMARY OF BACKGROUND DATA

Thymoma is a rare slow-growing cancer arising in the mediastinum. Thymomas usually grow invasively into surrounding structures. Distal spinal metastasis is uncommon. To date, only 4 cases with histological verification have been described.

METHODS

Patient 1: A 42-year-old female complained about back pain for 4 years. She underwent gross-total resection of a type B2 thymoma 8 years earlier without adjuvant therapy. Neurological examination revealed no deficits. Magnetic resonance imaging demonstrated an intraspinal extradural tumor at the level of L4-S1 with infiltration of vertebral body L5. A nearly total resection was performed via a partial L4 and L5 hemilaminectomy.Patient 2: A 62-year-old female was referred with segmental thoracic pain. She underwent a total of 6 surgical procedures for resection of a thymic carcinoma during a period of 13 years with a subsequently local radiation therapy and various chemotherapy cycles. Magnetic resonance imaging revealed an intraspinal extradural tumor at the level of T9-T10 with infiltration of vertebral body T9-T10. A gross-total tumor resection was performed via a costotransversectomy and facetectomy T9-T10.

RESULTS

Patient 1: The tumor cells were strongly positive for AE1/3- and CK5/14-specific antibodies. Most of the immature T-cells expressed CD3. CD1a, CD5, and TdT expression was observed in a smaller portion. The findings were consistent with the diagnosis of a spinal metastasis of the known type B2 thymoma.Patient 2: The tumor cells were CK5/14 and CK19/20 positive. Only the infiltrating lymphocytes were labeled with CD3-specific antibodies. Histopathological findings revealed a metastasis of a previously resected well-differentiated thymus carcinoma.

CONCLUSION

We recommend surgical resection because metastasis of thymoma may infiltrate nerve roots and compress the spinal cord. A multidisciplinary approach is required to manage long-term sequelae.

Thymic neoplasm: a rare disease with a complex clinical presentation

Thymic neoplasms constitute a broad category of rare lesions with a wide spectrum of pathologic characteristics and clinical presentations which therefore require a high index of suspicion to diagnose. The natural history of the disease is seldom predictable, anywhere from an indolent to an aggressively malignant course. Although the classification and staging of these lesions are complex and controversial, complete radical surgical resection remains the gold standard of therapy. Radiation and chemotherapy are important elements of the multimodality approach to treating these patients and it is important for thoracic surgeons to work closely with their colleagues in other disciplines in the management of and future research endeavors in thymic neoplasm. In this review, we discuss the evaluation of the patient with an anterior mediastinal mass, the classification and staging of thymic neoplasms, the role of surgery, radiation and chemotherapy in treating this disease, as well as future directions in research for novel targeted therapies.

Molecular aspects of thymic carcinoma

Thymic carcinomas are tumors of the anterior mediastinum derived from the epithelial cells of the thymic gland. Due to their low incidence they are often investigated in combination with thymomas under the rubric of "thymic epithelial neoplasms" and studies exclusively addressing thymic carcinomas are sparse. Thymic carcinomas are characterized by their histologic variability, often resembling tumors seen in other organ systems. This morphologic variation coupled with their rarity has prevented large scale research of these tumors and little is known about the etiology, biologic behavior or best treatment for thymic carcinoma. In recent years, attempts have been made to investigate the molecular characteristics of these tumors in the hope that molecular profiling can be used to predict the prognosis or lead to the development of new treatment strategies. Herein we provide an overview of the recent advances of the molecular analysis of thymic carcinoma with particular emphasis on the potential use for molecularly targeted therapies.

Micronodular thymic carcinoma with lymphoid hyperplasia: a clinicopathological and immunohistochemical study of five cases

Five cases of an unusual variant of thymic carcinoma are described, which represent the counterpart of the so-called micronodular thymoma with lymphoid hyperplasia. The patients were three men and two women aged 42-78 years (mean 64 years). Three patients were asymptomatic and the tumors were found incidentally on chest radiographs performed for unrelated reasons. Two patients complained of dyspnea, chest pain and shortness of breath prompting further investigations. The tumors ranged in size from 3.2 to 10.0 cm and were described as infiltrative masses often invading adjacent structures. Prominent cystic changes were not identified. Histologically, the neoplasms were composed of epithelial tumor cells arranged in a micronodular growth pattern set in a stroma showing florid lymphoid hyperplasia. Contrary to micronodular thymoma, the epithelial cell component of the present cases showed unequivocal signs of malignancy characterized by cytological atypia and increased mitotic activity. Immunohistochemical studies showed the lymphoid component to be of mixed B- and T-cell lineage. None of the patients had a history of myasthenia gravis or other autoimmune disorder. Follow-up revealed that 4 patients were alive and well 3-26 months after diagnosis while 1 patient was dead of disease 21 months after diagnosis. The tumors in this series represent a distinct subtype of thymic carcinoma histologically strongly resembling micronodular thymoma with lymphoid hyperplasia. Awareness of this type of thymic carcinoma is important in order not to dismiss this tumor for a neoplasm of lower-grade malignancy.

Respiratory Tract and Mediastinum

Normal cytology, abnormal and atypical cells, non-cellular components, and infectious cell changes are largely described together with benign, malignant, and neuroendocrine lesions regarding exfoliative and aspiration cytology of the lung. A separate section broadly addresses diagnostic findings and differential diagnoses in bronchoalveolar washings.

The section ‘Fine needle aspiration biopsy of mediastinal disorders’ covers in particular biopsy techniques, accuracy of liquid-based cytology, and the complex lesions of the thymus gland. Cytodiagnostic algorithms of the major benign and malignant pulmonary and mediastinal lesions and their respective differential diagnoses are additionally presented in synoptic setups.

Chronic shoulder pain referred from thymic carcinoma: a case report and review of literature

We report a case of thymic carcinoma presenting as unilateral shoulder pain for 13 months. Before an accurate diagnosis was made, the patient received conservative treatment, cervical discectomies, and myofascial trigger point injection, none of which relieved his pain. When thymic carcinoma was eventually diagnosed, he received total resection of the tumor and the shoulder pain subsided completely. Thymic carcinoma is a rare carcinoma, and our review of the literature did not show shoulder pain as its initial presentation except for one case report. The purpose of this report is to document our clinical experience so that other physiatrists can include thymic carcinoma in their differential diagnosis of shoulder pain.

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.

Ectopic thymic carcinoma in the neck

Thymic carcinoma is a rare tumor arising from the thymus, which is most commonly located in the anterior mediastinum. We report a 24-year-old woman who presented with a neck tumor. The patient underwent complete resection and the pathology sections showed thymic carcinoma. The patient received adjuvant chemotherapy and radiotherapy. After a 6-month follow-up, the patient is well without any evidence of recurrence.

Giant-cell anaplastic carcinoma with osteoclastic giant cells of the chest cavity: a distinctive form of thymic carcinoma?

Here, the authors describe a case of giant-cell anaplastic carcinoma with osteoclastic giant cells of the chest cavity-which could be a distinctive form of thymic carcinoma-which expressed CD5 and CD45. To the authors' knowledge, there has been no previous report on this subject. A 62-year-old woman presented with continuous pain in the left back associated with coughing and shortness of breath for more than 2 months prior to referral to the hospital. Palliative resection of a mediastinal tumor was performed. During the operation, it was found that the mass occupied most of the chest invading the chest wall, aorta, vena cava, and lung tissue. The patient soon died from diabetic complications in spite of anti-infection treatment. The tumor was composed of large areas of necrosis and anaplastic neoplastic giant cells with high mitotic activity, and osteoclast-like cells; there was marked inflammatory cell infiltration. The anaplastic neoplastic giant cells were immunoreactive for CKpan, CD5, CD45, VIM, and p53. Approximately 50% to 60% of the tumor cells showed immunoreactivity for Ki-67. In situ hybridization for Epstein-Barr virus-encoded RNA was negative for tumor cells and nonneoplastic osteoclastic giant cells. Because this tumor is very rare, extensive clinical, radiological, and morphological examinations as well as immunohistochemical studies are essential to make the diagnosis.