Primary Mediastinal Classical Hodgkin Lymphoma

Contrast-enhanced CT-based radiomics differentiate anterior mediastinum lymphoma from thymoma without myasthenia gravis and calcification

AIM

To explore the value of a radiomics model based on enhanced computed tomography (CT) in differentiating anterior mediastinal lymphoma (AML) and thymoma without myasthenia gravis (MG) and calcification.

MATERIALS AND METHODS

The present study analysed patients who were diagnosed histologically with AML and thymoma in three independent institutions. All pre-treatment patients underwent enhanced CT. In the training group of patients from institutions 1 (the First Affiliated Hospital of Kunming Medical University) and 3 (the Yunnan Cancer Hospital), two radiologists independently analysed the enhanced CT images and performed manual segmentation of each tumour. Radiomics features were screened using interobserver interclass coefficient (ICC) analysis, feature correlation analysis, and L1 regularisation. The discriminative efficacy of the logistic regression model was evaluated using receiver operating characteristic (ROC) analysis. Validation group of patients from institution 2 (the Second Affiliated Hospital of Zhejiang University School of Medicine) was used to validate the proposed models.

RESULTS

A total of 114 patients were enrolled in this study and 1,743 radiomics features were extracted from the enhanced CT images. After feature screening, the remaining 37 robust radiomics features were used to construct the model. In the training group, the AUC of the model was 0.987 (95% confidence interval [CI]: 0.976-0.999), the sensitivity, specificity, and accuracy were 0.912, 0.946, and 0.924, respectively. In the validation group, the AUC of the model was 0.798 (95% CI: 0.683-0.913), the sensitivity, specificity, and accuracy were 0.760, 0.700, and 0.743, respectively.

CONCLUSION

The radiomics model created provided effective information to assist in the selection of clinical strategies, thus reducing unnecessary procedures in patients with AML and guiding direct surgery in patients with thymoma to avoid biopsy.

Abnormal Presentation and Challenging Diagnosis of Mediastinal Lymphoma: A Case Report

We describe a rare case of classical Hodgkin lymphoma (HL) in a 20-year-old female patient. She presented to our hospital with chest wall swelling after months of post-chest trauma management. The swelling was initially treated as an infected hematoma, and the patient was referred for surgical evacuation. During the surgery, the swelling was found to be a mass that extended to the mediastinum. A biopsy was taken, which later resulted in the diagnosis of a granular cell tumor (GCT). A decision on surgical resection by video-assisted thoracoscopic surgery (VATS) was taken after discussion with the multidisciplinary team of surgery, cardiothoracic surgery, oncology, pathology, and radiology. During the surgery, a frozen section biopsy was taken, which showed no features of lymphoma or granular cell tumors. The surgery was followed by a midline sternotomy to control the bleeding from an accidentally injured major vessel. The bleeding was controlled, and the mass was dissected and sent for histopathological examination. The histopathology showed nodular classical HL features, and the patient was referred for chemotherapy. In our case, the patient was initially diagnosed with GCT, but with complete resection and an adequate biopsy, the mass was found to be a classical HL. Possible cross-cellularity is questioned, and the possible correlation between the two findings encouraged us to report this case.

Differentiation between rebound thymic hyperplasia and thymic relapse after chemotherapy in pediatric Hodgkin lymphoma

BACKGROUND

Rebound thymic hyperplasia (RTH) is a common phenomenon caused by stress factors such as chemotherapy (CTX) or radiotherapy, with an incidence between 44% and 67.7% in pediatric lymphoma. Misinterpretation of RTH and thymic lymphoma relapse (LR) may lead to unnecessary diagnostic procedures including invasive biopsies or treatment intensification. The aim of this study was to identify parameters that differentiate between RTH and thymic LR in the anterior mediastinum.

METHODS

After completion of CTX, we analyzed computed tomographies (CTs) and magnetic resonance images (MRIs) of 291 patients with classical Hodgkin lymphoma (CHL) and adequate imaging available from the European Network for Pediatric Hodgkin lymphoma C1 trial. In all patients with biopsy-proven LR, an additional fluorodeoxyglucose (FDG)-positron emission tomography (PET)-CT was assessed. Structure and morphologic configuration in addition to calcifications and presence of multiple masses in the thymic region and signs of extrathymic LR were evaluated.

RESULTS

After CTX, a significant volume increase of new or growing masses in the thymic space occurred in 133 of 291 patients. Without biopsy, only 98 patients could be identified as RTH or LR. No single finding related to thymic regrowth allowed differentiation between RTH and LR. However, the vast majority of cases with thymic LR presented with additional increasing tumor masses (33/34). All RTH patients (64/64) presented with isolated thymic growth.

CONCLUSION

Isolated thymic LR is very uncommon. CHL relapse should be suspected when increasing tumor masses are present in distant sites outside of the thymic area. Conversely, if regrowth of lymphoma in other sites can be excluded, isolated thymic mass after CTX likely represents RTH.

The Co-Existence of Micronodular Thymoma and Lymphoma: A Clinicopathological and Immunohistochemical Study of Two Cases

Two cases with the co-existence of micronodular thymoma and lymphoma are presented. The patients are two female patients 54 and 60 years of age who presented with symptoms of chest pain, general malaise, cough, and dyspnea. Diagnostic imaging demonstrated the presence of an anterior mediastinal mass. Initial biopsy was interpreted as an epithelial neoplasm compatible with thymoma. Surgical resection took place demonstrating the presence of micronodular thymoma in both cases. In addition, in both cases the lymphoid proliferation infiltrated surrounding adipose tissue. However, in one case the lymphoid proliferation was composed of atypical lymphocytes with irregular nuclei and increase mitotic activity positive for CD3 and TDT, while in the second case, the lymphoid proliferation was composed of more mature lymphocytes with a monocytoid appearance and positive for CD20. Both of these cases represent an unusual association and one that must be kept in the differential diagnosis especially in cases of micronodular thymoma.

Characterization of Mediastinal Bulky Lymphomas with FDG-PET-Based Radiomics and Machine Learning Techniques

BACKGROUND

This study tested the diagnostic value of 18F-FDG PET/CT (FDG-PET) volumetric and texture parameters in the histological differentiation of mediastinal bulky disease due to classical Hodgkin lymphoma (cHL), primary mediastinal B-cell lymphoma (PMBCL) and grey zone lymphoma (GZL), using machine learning techniques.

METHODS

We reviewed 80 cHL, 29 PMBCL and 8 GZL adult patients with mediastinal bulky disease and histopathological diagnoses who underwent FDG-PET pre-treatment. Volumetric and radiomic parameters were measured using FDG-PET both for bulky lesions (BL) and for all lesions (AL) using LIFEx software (threshold SUV ≥ 2.5). Binary and multiclass classifications were performed with various machine learning techniques fed by a relevant subset of radiomic features.

RESULTS

The analysis showed significant differences between the lymphoma groups in terms of SUVmax, SUVmean, MTV, TLG and several textural features of both first- and second-order grey level. Among machine learning classifiers, the tree-based ensembles achieved the best performance both for binary and multiclass classifications in histological differentiation.

CONCLUSIONS

Our results support the value of metabolic heterogeneity as an imaging biomarker, and the use of radiomic features for early characterization of mediastinal bulky lymphoma.

Multiparameter diagnostic model based on 18F-FDG PET and clinical characteristics can differentiate thymic epithelial tumors from thymic lymphomas

OBJECTIVE

To evaluate the diagnostic performance of combined multiparametric ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸FDG PET) with clinical characteristics in differentiating thymic epithelial tumors (TETs) from thymic lymphomas.

PATIENTS AND METHODS

A total of 173 patients with 80 TETs and 93 thymic lymphomas who underwent ¹⁸F-FDG PET/CT before treatment were enrolled in this retrospective study. All patients were confirmed by pathology, and baseline characteristics and clinical data were also collected. The semi-parameters of ¹⁸F-FDG PET/CT, including lesion size, SUVmax (maximum standard uptake value), SUVmean (mean standard uptake value), TLG (total lesion glycolysis), MTV (metabolic tumor volume) and SUVR (tumor-to-normal liver standard uptake value ratio) were evaluated. The differential diagnostic efficacy was evaluated using the receiver operating characteristic (ROC) curve. Integrated discriminatory improvement (IDI) and net reclassification improvement (NRI), and Delong test were used to evaluate the improvement in diagnostic efficacy. The clinical efficacy was evaluated by decision curve analysis (DCA).

RESULTS

Age, clinical symptoms, and metabolic parameters differed significantly between patients with TETs and thymic lymphomas. The ROC curve analysis of SUVR showed the highest differentiating diagnostic value (sensitivity = 0.763; specificity = 0.888; area under the curve [AUC] = 0.881). The combined diagnostics model of age, clinical symptoms and SUVR resulted in the highest AUC of 0.964 (sensitivity = 0.882, specificity = 0.963). Compared with SUVR, the diagnostic efficiency of the model was improved significantly. The DCA also confirmed the clinical efficacy of the model.

CONCLUSIONS

The multiparameter diagnosis model based on ¹⁸F-FDG PET and clinical characteristics had excellent value in the differential diagnosis of TETs and thymic lymphomas.

Diagnostic Challenges in the Cytology of Thymic Epithelial Neoplasms

Simple Summary

Thymic epithelial neoplasms, including thymoma, thymic carcinoma, and thymic neuroendocrine neoplasms, constitute the majority of anterior mediastinal masses. Fine needle aspirations (FNA) of mediastinal masses are infrequently encountered and are highly challenging to interpret. Thymic neoplasms display a significant degree of histologic diversity and have overlapping morphologic features with tumors from other sites. However, when properly interpreted alongside ancillary studies and radiologic findings, FNAs can yield clinically actionable results. This review aims to illustrate the usefulness and diagnostic pitfalls of thymic FNAs to assist pathologists in analyzing these specimens.

Abstract

Thymic epithelial neoplasms are rare tumors that constitute the majority of anterior mediastinal masses. They are classified as thymomas, thymic carcinomas, and thymic neuroendocrine neoplasms. Biopsy diagnosis is not common, and most tumors are surgically resected. Biopsy, including cytology, is indicated when a non-surgical entity is suspected or in cases of locally advanced disease. Smears of thymomas consist of round or spindle epithelial cells admixed with varying amounts of lymphocytes depending on the type of thymoma. Smears of thymic carcinoma and thymic neuroendocrine neoplasms are often indistinguishable from corresponding tumor types from other organs. Accurate cytological diagnosis can be difficult due to the histological diversity of thymomas, as well as the morphological features that certain thymic tumors share with similar tumors from other organs. However, fine needle aspiration (FNA) of anterior mediastinal masses can provide clinically actionable information and can be used to determine whether lesions require surgical, systemic, or local noninvasive treatments. Ancillary studies, namely, immunocytochemical stains, flow cytometry, and radiology, are important tools in the evaluation of thymic aspirates. This review discusses the utility and limitations of thymic FNAs and illustrates the diagnostic features and pitfalls of these specimens.

[Mediastinal lesions : The most common pathologies in chest X-rays and their correlations in computed tomography]

BACKGROUND

Many pathologies of the mediastinum can be diagnosed using standard radiographs. Correlation of radiographic findings with computed tomography (CT) is instructive for a better understanding and can help improve detection rates of mediastinal lesions.

OBJECTIVES

To identify the most common mediastinal lesions and to correlate their features in chest radiographs and CT.

METHODS

The International Thymic Malignancy Interest Group (ITMIG) classification in the anterior, middle, and posterior mediastinum is based on anatomic landmarks. Used as a tool to characterize mediastinal lesions this classification is applied in this article.

RESULTS

The most common lesions include mediastinal goiter, germ cell and thymic neoplasms in the anterior mediastinum, lymphadenopathy in the middle mediastinum, and neurogenic neoplasms in the posterior mediastinum. Other lesions of neoplastic or non-neoplastic origin can be distinguished in the three compartments and should be considered in the differential diagnosis.

CONCLUSIONS

Knowledge of the most common pathologies in the three mediastinal compartments can accelerate differential diagnosis. Understanding the normal mediastinal lines is key in anatomic localization and detection of many lesions in chest radiographs.

Mediastinal Lymphoproliferative Disorders

Lymphoproliferative disorders comprise 50% to 60% of all mediastinal malignancies in both children and adults. Primary mediastinal involvement is rare (∼5%), whereas secondary mediastinal involvement by systemic disease is more common (10% to 25%). Primary mediastinal disease is defined as involvement by a lymphoproliferative disorder of mediastinal lymph nodes, the thymus, and/or extranodal mediastinal organs without evidence of systemic disease at presentation. In this review, the clinical, radiologic, histopathologic, immunohistochemical, and genetic features of some of the most characteristic mediastinal lymphoproliferative disorders are presented. The entities discussed here include: classic Hodgkin lymphoma with emphasis on nodular sclerosis and mixed cellularity types, and non-Hodgkin lymphomas, including primary mediastinal (thymic) large B-cell lymphoma, mediastinal gray zone lymphoma, mediastinal diffuse large B-cell lymphoma, thymic marginal zone lymphoma, mediastinal plasmacytoma, T-lymphoblastic lymphoma, and anaplastic large cell lymphoma. Although not a malignant process, hyaline vascular Castleman disease is also discussed here as this disorder commonly involves the mediastinum. Despite multiple advances in hematopathology in recent decades, the day-to-day diagnosis of these lesions still requires a morphologic approach and a proper selection of immunohistochemical markers. For this reason, it is crucial for general pathologists to be familiar with these entities and their particular clinicoradiologic presentation.

Multilocular thymic cyst (MTC) and other tumors with MTC features: Pitfalls in diagnosis

Cystic lesions of the anterior mediastinum represent a well-known group of benign lesions that are relatively common in the general practice, namely in the pediatric age group. In the adult population, multilocular thymic cyst (MTC) plays an important role in occurrence as it presents as a cystic anterior mediastinal mass that clinically may mimic another anterior mediastinal tumor. In general, MTC is of rather unusual occurrence and its histopathological features have been well described in the literature. However, similar histopathological features may also be associated with a gamut of other tumoral conditions that although unrelated may be encountered growing along the walls of these cystic structures. Herein a presentation of the classical MTC and the classical histopathological features of such entity in association with other tumoral conditions will be discussed. It is highly important to underscore that the final interpretation of some of these tumors is based on a thorough evaluation of the cystic lesion and a reasonable sampling for histological evaluation so that the proper interpretation can be reached. Needless to say, the radiological and clinical information of the patients with cystic anterior mediastinal lesions is very important in the final analysis of these cases.

Imaging of the Anterior/Prevascular Mediastinum

Prevascular mediastinal masses include a wide range of benign and malignant entities. Localization of mediastinal masses to specific compartments together with characteristic imaging findings and demographic and clinical information allows formulation of a focused differential diagnosis. Radiologists may use these methods to distinguish between surgical and nonsurgical cases and thus inform patient management and have an impact on outcomes. Treatment of choice varies based on the pathology, ranging from no intervention or serial imaging follow-up to surgical excision, chemotherapy, and/or radiation.

Feasibility of using dynamic contrast-enhanced MRI for differentiating thymic carcinoma from thymic lymphoma based on semi-quantitative and quantitative models

AIM

To evaluate the value of using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) derived parameters to differentiate thymic carcinoma and thymic lymphoma based on semi-quantitative and quantitative models.

MATERIALS AND METHODS

Twenty-nine pathologically confirmed anterior mediastinum tumours in 29 patients were enrolled in this retrospective study, including 15 thymic carcinoma and 14 lymphoma patients. All the patients underwent pre-treatment mediastinum DCE-MRI. Both semi-quantitative and quantitative parameters were calculated and the volume transfer constant K^trans, the flux rate constant between extravascular extracellular space and plasma k_ep, the extravascular extracellular volume fraction v_e were obtained based on a modified Tofts model. DCE-MRI derived parameters were compared between thymic carcinoma and thymic lymphoma groups.

RESULTS

Thymic carcinoma had significantly lower k_ep (p=0.040) and higher v_e (p=0.018) than thymic lymphoma; however, there were no significant differences on K^trans and semi-quantitative parameters between the two groups. v_e had the highest area under the curve (cut-off value, 0.282; area under the curve, 0.748; sensitivity, 71.4%; specificity, 80%). The combination of k_ep and v_e could increase the diagnostic performance significantly (area under the curve, 0.752; sensitivity, 57.1%; specificity, 93.3%).

CONCLUSION

DCE-MRI derived parameters may have value in the differentiating thymic carcinoma and thymic lymphoma.

A Whole-Tumor Histogram Analysis of Apparent Diffusion Coefficient Maps for Differentiating Thymic Carcinoma from Lymphoma

Objective

To assess the performance of a whole-tumor histogram analysis of apparent diffusion coefficient (ADC) maps in differentiating thymic carcinoma from lymphoma, and compare it with that of a commonly used hot-spot region-of-interest (ROI)-based ADC measurement.

Materials and Methods

Diffusion weighted imaging data of 15 patients with thymic carcinoma and 13 patients with lymphoma were retrospectively collected and processed with a mono-exponential model. ADC measurements were performed by using a histogram-based and hot-spot-ROI-based approach. In the histogram-based approach, the following parameters were generated: mean ADC (ADC_mean), median ADC (ADC_median), 10th and 90th percentile of ADC (ADC₁₀ and ADC₉₀), kurtosis, and skewness. The difference in ADCs between thymic carcinoma and lymphoma was compared using a t test. Receiver operating characteristic analyses were conducted to determine and compare the differentiating performance of ADCs.

Results

Lymphoma demonstrated significantly lower ADC_mean, ADC_median, ADC₁₀, ADC₉₀, and hot-spot-ROI-based mean ADC than those found in thymic carcinoma (all p values < 0.05). There were no differences found in the kurtosis (p = 0.412) and skewness (p = 0.273). The ADC₁₀ demonstrated optimal differentiating performance (cut-off value, 0.403 × 10^-3 mm²/s; area under the receiver operating characteristic curve [AUC], 0.977; sensitivity, 92.3%; specificity, 93.3%), followed by the ADC_mean, ADC_median, ADC₉₀, and hot-spot-ROI-based mean ADC. The AUC of ADC₁₀ was significantly higher than that of the hot spot ROI based ADC (0.977 vs. 0.797, p = 0.036).

Conclusion

Compared with the commonly used hot spot ROI based ADC measurement, a histogram analysis of ADC maps can improve the differentiating performance between thymic carcinoma and lymphoma.

Hodgkin's lymphoma and its association with EBV and HIV infection

Hodgkin's lymphoma (HL) constitutes a clonal expansion of what appears to be malignant B cells. Viruses are involved in its pathogenesis, such as the Epstein-Barr virus (EBV) and human immunodeficiency virus (HIV). Since these viral infections have been shown to play key roles in the pathogenesis of HL, countries with a prevalence of HIV and EBV represent interesting population targets to study the pathogenesis of HL, linking the evolution of the disease with viral infections. Usually, patients present with late stage disease often involving the bone marrow at the time of diagnosis. The present paper discusses the role of viral infection in African countries, as HL is considered to be a malignant disease characterized by an inflammatory reaction to an aberrant B cell clone that is well known as the Reed-Sternberg cell (HRS).

Primary Salivary Gland Type Tumors of the Thymus

The existence of primary salivary gland type tumors (SGTs), similar to those occurring in the major salivary glands, is well known in the thoracic cavity. When they occur in this anatomic area, these tumors more commonly arise from the lung. However, the existence of these tumors primarily affecting the thymus, although recognized in the literature, is rather not well documented or known. In addition, contrary to the primary lung SGTs, which are predominantly of the malignant type, these tumors when occur in thymus encompass a wider spectrum of biology ranging from benign to low grade, and high grade malignancy. The recognition of SGTs in the thymus, even though rare, is important to properly address treatment and prognosis. Herein, we will discuss the numerous benign a malignant SGTs that have been described in the thymus and highlight the difficulty that these tumors may pose when occurring in the thymic area.