TNM Staging System in Thymoma: A Critical Appraisal?

Thymomas are rare tumors of the anterior mediastinum with peculiar clinical and pathological features. They have been deeply analyzed by pioneer authors, who strictly linked their name to the main pathological and staging classifications. Before the latest edition of the WHO classification of thymic epithelial tumors, the history of thymoma pathological classification inherited the name of the pathologists who systematically addressed the issue, from Levine-Rosai to Muller-Hermelink. Similarly, the thymoma staging system is intimately related to the name of two surgeons, Masaoka and Koga, who historically dealt with this disease. More recently, the traditional tumor-nodes-metastasis (TNM) system has been developed for the staging of this condition, in a rational attempt to put thymomas in conformity with the other solid tumors. The efforts of the International Thymic Malignancies Interest Group (ITMIG) and the Thymic Domain of the Staging and Prognostic Factors Committee (TD-SPFC) of the International Association for the Study of Lung Cancer (IASLC) resulted in the TNM classification of thymic tumors, which have been included in the eighth edition of the American Joint Committee on Cancer's (AJCC) Cancer Staging Manual. Herein, we report a narrative review of the evolution of the thymic epithelial tumors (TET) staging system and present a critical appraisal of the actual TNM classification compared with the historical Masaoka-Koga classification, with special focus on the proposal for the ninth edition of the TNM, expected in 2024.

Mark Wick contributions to pathology of the mediastinum

Mark Wick made a wide range of contributions to the field of mediastinal pathology. Early papers amplified the spectrum of neuroendocrine carcinomas of the thymus and brought attention to the aggressive nature of this tumor, also highlighting the occurrence of coexisting carcinoid tumor and small cell carcinoma of this organ. The controversial issue of thymoma classification was addressed in several papers and editorial comments, while also reporting a case of metastatic thymoma. A series of thymic carcinomas as well a report on the unusual clear cell variant bear his name as one of the authors. He summarized the topic of mediastinal cyst in a review published in 2005. Sarcomas arising in mediastinal germ cell tumors were also within the purview of his interests, with a publication of series of seven cases. He reviewed the topic of inflammatory myofibroblastic tumor of the heart and added a case to the existing literature. Two books dedicated to different aspect of mediastinal pathology also carry his name in the front cover in association with Drs Taazelar in one and Marchevsky in the other.

On the Histologic Classification of Thymoma

The classification of thymoma continues to be a source of controversy in pathology. The difficulties in histologic classification are evident from the number of proposals that have been offered over the years, as well as for the continuous changes and modifications introduced by the World Health Organization to their classification system over the past 20 years. We analyze here some of the issues involved in the classification of these tumors and the difficulties encountered for practicing pathologists in deciphering the "letters and numbers" system devised by the World Health Organization. We would like to propose an alternate approach to thymoma histologic classification that capitalizes on the basic observation of their cytologic features and incorporates the pattern of growth resulting from the interplay of the tumor cells with other cellular constituents as a secondary characteristic. The proposed histologic classification provides a simplified, reproducible means of histologically categorizing these tumors and can be easily understood by most practicing pathologists in simple and clear morphologic terms.

Dataset for reporting of thymic epithelial tumours: recommendations from the International Collaboration on Cancer Reporting (ICCR)

AIMS

Thymic epithelial tumours (TET), including thymomas and thymic carcinomas and thymic neuroendocrine neoplasms, are malignant neoplasms that can be associated with morbidity and mortality. Recently, an updated version of the World Health Organization (WHO) Classification of Thoracic Tumours 5th Edition, 2021 has been released, which included various changes to the classification of these neoplasms. In addition, in 2017 the Union for International Cancer Control (UICC) / American Joint Committee on Cancer (AJCC) published the 8th Edition Staging Manual which, for the first time, includes a TNM staging that is applicable to thymomas, thymic carcinomas, and thymic neuroendocrine neoplasms.

METHODS AND RESULTS

To standardize reporting of resected TET and thymic neuroendocrine neoplasms the accrediting bodies updated their reporting protocols. The International Collaboration on Cancer Reporting (ICCR), which represents a collaboration between various National Associations of Pathology, updated its 2017 histopathology reporting guide on TET and thymic neuroendocrine neoplasms accordingly. This report will highlight important changes in the reporting of TET and thymic neuroendocrine neoplasms based on the 2021 WHO, emphasize the 2017 TNM staging, and also comment on the rigour and various uncertainties for the pathologist when trying to follow that staging.

CONCLUSION

The ICCR dataset provides a comprehensive, standardized template for reporting of resected TET and thymic neuroendocrine neoplasms.

Thymoma: An Overview

Thymomas are considered one of the most prevalent types of mediastinal epithelial tumors, which frequently develop in the anterior mediastinum. Due to their rarity, these tumors' nomenclature, classification, and staging are likely to be the subject of debate and argument for most expert pathologists. Furthermore, the significance of thymoma histologic classifications have been debated over the past twenty years. While certain advocates argue that staging at the time of diagnosis is more significant, others believe that histologic subtyping has a significant impact on how patients behave clinically. In this review, we will focus on some of the challenges that diagnostic surgical pathologists may experience while evaluating the histopathology of thymomas and staging these tumors. We will additionally glance over the clinical characteristics of these distinct tumors and the current management strategy.

Pathologists should probably forget about kappa. Percent agreement, diagnostic specificity and related metrics provide more clinically applicable measures of interobserver variability

Kappa statistics have been widely used in the pathology literature to compare interobserver diagnostic variability (IOV) among different pathologists but there has been limited discussion about the clinical significance of kappa scores. Five representative and recent pathology papers were queried using clinically relevant specific questions to learn how IOV was evaluated and how the clinical applicability of results was interpreted. The papers supported our anecdotal impression that pathologists usually assess IOV using Cohen's or Fleiss' kappa statistics and interpret the results using some variation of the scale proposed by Landis and Koch. The papers did not cite or propose specific guidelines to comment on the clinical applicability of results. The solutions proposed to decrease IOV included the development of better diagnostic criteria and additional educational efforts, but the possibility that the entities themselves represented a continuum of morphologic findings rather than distinct diagnostic categories was not considered in any of the studies. A dataset from a previous study of IOV reported by Thunnissen et al. was recalculated to estimate percent agreement among 19 international lung pathologists for the diagnosis of 74 challenging lung neuroendocrine neoplasms. Kappa scores and diagnostic sensitivity, specificity, positive and negative predictive values were calculated using the majority consensus diagnosis for each case as the gold reference diagnosis for that case. Diagnostic specificity estimates among multiple pathologists were > 90%, although kappa scores were considerably more variable. We explain why kappa scores are of limited clinical applicability in pathology and propose the use of positive and negative percent agreement and diagnostic specificity against a gold reference diagnosis to evaluate IOV among two and multiple raters, respectively.

Histotyping of Indian thymomas: A clinicopathologic study from north India

Background & objectives:

Thymomas are rare, but most common anterior mediastinal lesions. The histomorphologic spectrum of thymic epithelial tumours (TETs) in Indian population has not been explored in depth. This study was aimed to assess the histomorphology of TETs in the Indian patients and correlate clinical parameters with pathological features.

Methods:

It was a retrospective study conducted in a tertiary referral hospital in north India. All morphologically confirmed cases of TETs since 2009 were included. Clinical details and histology slides were reviewed using the Modified Masaoka-Koga staging system and WHO 2015 classification. Clinicopathological correlation and survival analysis were done. A comparative review from other published Indian studies was performed.

Results:

A total of 219 cases of TETs (138 resections and 81 biopsies) were identified. The most common histomorphologic type was B2, and the most frequent stage was I. Types A/AB were common in older age (P<0.01). Clinically, higher stage tumours were found mostly in men (P<0.01), and these were Type B thymomas (P<0.01). Myasthenia gravis was more common in women (P<0.02) and in lower stages (P<0.05). Survival analysis revealed significant association between recurrence and tumour stage. Although thymic carcinoma was diagnosed on biopsy, no resectable case was identified.

Interpretation & conclusions:

Our findings showed that the thymomas in Indian patients were most commonly Stage I tumours of B2 and AB histotypes. Resected thymic carcinomas were conspicuously absent in our study. More studies need to be done to establish the frequency and biology of TETs from India.

Evolution of Classification of Thymic Epithelial Tumors in the Era of Dr Thomas V. Colby

CONTEXT

-Numerous histomorphologic and staging classifications of thymic epithelial tumors (TETs) have been proposed during the last century, suggesting that the classification of these tumors is challenging and controversial. Difficulties of classifying TETs include various combinations of epithelial cells and lymphocytes and the paucity of these tumors. The prognostic significance, specifically of the histomorphologic classifications, has been debated. Early classifications were also challenged by the uncertainty of the neoplastic component(s) of the tumor.

OBJECTIVE

-To discuss the evolution of the histomorphologic classification and the staging system of TET. Controversies and problems of some classifications and their importance for therapeutic management and prognosis will be reviewed. Classifications that incorporated new concepts and approaches at the time or outcome studies will be highlighted. Current classifications will be discussed and the staging system that was recently proposed for the upcoming eighth American Joint Committee on Cancer staging will be described.

DATA SOURCES

-Search of literature database (PubMed) and current (2015) World Health Organization classification.

CONCLUSIONS

-Histomorphologic and staging classifications of TET have evolved during the last century and especially during the era of Thomas V. Colby, MD. Evidence supports that the staging system has prognostic implications independent of and superior to the histomorphologic classification. Histomorphology appears to be important for biologic features of TET.

Metastatic type A thymoma: morphological and genetic correlation

AIMS

The vast majority of type A thymomas are diagnosed in tumour stages 1 or 2, and metastatic cases are exceedingly rare. The histological and genetic features of such metastatic type A thymomas have not been described in detail.

METHODS AND RESULTS

Five metastatic type A thymomas in tumour stage Masaoka IVb that had been reviewed by a panel of expert pathologists were analysed using comparative genomic hybridization (CGH). Cases 1, 2 and 3 showed the prototypical morphology of type A thymomas with mainly solid growth patterns. These cases displayed only very subtle nuclear irregularities and slight nuclear crowding, but no other atypical features. Mitoses were absent. Cases 3 and 4, in contrast, had a distinctly atypical morphology. CGH revealed partially recurrent alterations in four cases (with and without atypical morphology), including gains on chromosome 1q (one case), 17q (two cases), chromosome 19 (three cases) and 22q (one case) and losses on chromosome 17p (two cases) and 22q (one case).

CONCLUSION

Rare metastatic type A thymomas, both with typical and 'atypical' histological features, show partially recurrent genomic alterations that differ from the much more frequent localized and indolent tumours. The fact that these alterations were recurring points to a link between clinical behaviour and molecular features. Our findings may have implications for the management and treatment of such tumours.

Dataset for reporting of thymic epithelial tumours: recommendations from the International Collaboration on Cancer Reporting (ICCR)

AIMS

The International Collaboration on Cancer Reporting (ICCR) is a not-for-profit organization formed by the Royal Colleges of Pathologists of Australasia and the United Kingdom, the College of American Pathologists, the Canadian Association of Pathologists-Association Canadienne des Pathologists in association with the Canadian Partnership Against Cancer, and the European Society of Pathology. Its goal is to produce standardized, internationally agreed, evidence-based datasets for use throughout the world.

METHODS AND RESULTS

This article describes the development of a cancer dataset by the multidisciplinary ICCR expert panel for the reporting of thymic epithelial tumours. The dataset includes 'required' (mandatory) and 'recommended' (non-mandatory) elements, which are validated by a review of current evidence and supported by explanatory text. Seven required elements and 12 recommended elements were agreed by the international dataset authoring committee to represent the essential information for the reporting of thymic epithelial tumours.

CONCLUSIONS

The use of an internationally agreed, structured pathology dataset for reporting thymic tumours provides all of the necessary information for optimal patient management, facilitates consistent and accurate data collection, and provides valuable data for research and international benchmarking. The dataset also provides a valuable resource for those countries and institutions that are not in a position to develop their own datasets.

cFLIP overexpression in T cells in thymoma-associated myasthenia gravis

Objective

The capacity of thymomas to generate mature CD4+ effector T cells from immature precursors inside the tumor and export them to the blood is associated with thymoma-associated myasthenia gravis (TAMG). Why TAMG(+) thymomas generate and export more mature CD4+ T cells than MG(−) thymomas is unknown.

Methods

Unfixed thymoma tissue, thymocytes derived thereof, peripheral blood mononuclear cells (PBMCs), T-cell subsets and B cells were analysed using qRT-PCR and western blotting. Survival of PBMCs was measured by MTT assay. FAS-mediated apoptosis in PBMCs was quantified by flow cytometry. NF-κB in PBMCs was inhibited by the NF-κB-Inhibitor, EF24 prior to FAS-Ligand (FASLG) treatment for apoptosis induction.

Results

Expression levels of the apoptosis inhibitor cellular FLICE-like inhibitory protein (c-FLIP) in blood T cells and intratumorous thymocytes were higher in TAMG(+) than in MG(−) thymomas and non-neoplastic thymic remnants. Thymocytes and PBMCs of TAMG patients showed nuclear NF-κB accumulation and apoptosis resistance to FASLG stimulation that was sensitive to NF-κB blockade. Thymoma removal reduced cFLIP expression in PBMCs.

Interpretation

We conclude that thymomas induce cFLIP overexpression in thymocytes and their progeny, blood T cells. We suggest that the stronger cFLIP overexpression in TAMG(+) compared to MG(−) thymomas allows for the more efficient generation of mature CD4+ T cells in TAMG(+) thymomas. cFLIP overexpression in thymocytes and exported CD4+ T cells of patients with TAMG might contribute to the pathogenesis of TAMG by impairing central and peripheral T-cell tolerance.

The IASLC/ITMIG Thymic Epithelial Tumors Staging Project: proposal for an evidence-based stage classification system for the forthcoming (8th) edition of the TNM classification of malignant tumors

A universal and consistent stage classification system, which describes the anatomic extent of a cancer, provides a foundation for communication and collaboration. Thymic epithelial malignancies have seen little progress, in part because of the lack of an official system. The International Association for the Study of Lung Cancer and the International Thymic Malignancies Interest Group assembled a large retrospective database, a multispecialty international committee and carried out extensive analysis to develop proposals for the 8th edition of the stage classification manuals. This tumor, node, metastasis (TNM)-based system is applicable to all types of thymic epithelial malignancies. This article summarizes the proposed definitions of the T, N, and M components and describes how these are combined into stage groups. This represents a major step forward for thymic malignancies.

The IASLC/ITMIG Thymic Epithelial Tumors Staging Project: proposals for the T Component for the forthcoming (8th) edition of the TNM classification of malignant tumors

Despite longstanding recognition of thymic epithelial neoplasms, there is no official American Joint Committee on Cancer/Union for International Cancer Control stage classification. This article summarizes proposals for classification of the T component of stage classification for use in the 8th edition of the tumor, node, metastasis classification for malignant tumors. This represents the output of the International Association for the Study of Lung Cancer and the International Thymic Malignancies Interest Group Staging and Prognostics Factor Committee, which assembled and analyzed a worldwide database of 10,808 patients with thymic malignancies from 105 sites. The committee proposes division of the T component into four categories, representing levels of invasion. T1 includes tumors localized to the thymus and anterior mediastinal fat, regardless of capsular invasion, up to and including infiltration through the mediastinal pleura. Invasion of the pericardium is designated as T2. T3 includes tumors with direct involvement of a group of mediastinal structures either singly or in combination: lung, brachiocephalic vein, superior vena cava, chest wall, and phrenic nerve. Invasion of more central structures constitutes T4: aorta and arch vessels, intrapericardial pulmonary artery, myocardium, trachea, and esophagus. Size did not emerge as a useful descriptor for stage classification. This classification of T categories, combined with a classification of N and M categories, provides a basis for a robust tumor, node, metastasis classification system for the 8th edition of American Joint Committee on Cancer/Union for International Cancer Control stage classification.

Evidence-based pathology: systematic literature reviews as the basis for guidelines and best practices

CONTEXT

Evidence-based medicine has been proposed as a new paradigm for the identification and evaluation of medical information. Best available evidence or data are identified and used as the basis for the diagnosis and treatment of individual patients. Evidence-based pathology has adapted basic evidence-based medicine concepts to the specific needs of pathology and laboratory medicine.

OBJECTIVES

To briefly review the history and basic concepts of evidence-based medicine and evidence-based pathology, describe how to perform and interpret systematic reviews, and discuss how to integrate best evidence into guidelines.

DATA SOURCES

PubMed (National Library of Medicine, Washington, DC) and Web of Science (Thompson Reuters, New York, New York) were used.

CONCLUSIONS

Evidence-based pathology provides methodology to evaluate the quality of information published in pathology journals and apply it to the diagnosis of tissue samples and other tests from individual patients. Information is gathered through the use of systematic reviews, using a method that is less biased and more comprehensive than ad hoc literature searches. Published data are classified into evidence levels to provide readers with a quick impression about the quality and probable clinical validity of available information. Best available evidence is combined with personal experience for the formulation of evidence-based, rather than opinion-based, guidelines that address specific practice needs.

Multidisciplinary treatment of malignant thymoma

PURPOSE OF REVIEW

Thymomas are the most common tumors of the anterior mediastinum. Although surgery remains the only curative treatment, the use of multimodality therapy for primary unresectable thymomas has led to change the clinical management of these tumors.

RECENT FINDINGS

Nowadays Masaoka stage, WHO, and radical surgical resection are considered by many authors as independent prognostic factors for long-term survival. Radiotherapy may be useful as adjuvant therapy in cases of incomplete surgical resection with microscopic or macroscopic residual disease, or for those patients with locally advanced or metastatic unresectable disease. Chemotherapy is considered a valid option in selected patients with residual disease after local treatments or as a neoadjuvant approach to improve resectability in Masaoka stages III or IV-a thymomas. Currently, no standardized regimen for chemotherapy or agreed timing exists.

SUMMARY

So far, multimodality treatment has been related to low morbidity and long survival rate, but there are still many concerns regarding a different regimen of therapy and the correct timing.

Thymomas II: a clinicopathologic correlation of 250 cases with a proposed staging system with emphasis on pathologic assessment

We present 250 cases of thymomas with emphasis on their clinical staging and follow-up. The patients were 120 males and 130 females between the ages of 13 and 92 years. Surgical resection was performed and histopathologic material evaluated in every case. Grossly, the tumors resected varied in size from 3 to 20 cm in greatest diameter. According to our proposed staging system, 31 cases were stage 0, 128 were stage I, 70 stage II, and 21 stage III at the time of resection. Histologically, approximately 53% of thymomas were of mixed histologic types. Follow-up information ranging from 1 to 16 years was obtained, showing significant statistical P values of .044 and .016 for overall and recurrence-free survival, respectively. We consider that our proposed staging system offers better stratification of cases and improved histologic definitions for proper staging of cases of thymoma.

Staging system of thymoma

INTRODUCTION

Thirty years have gone by since the Masaoka staging system of thymoma was proposed in 1981. Although the Masaoka staging system has been accepted by many surgeons and pathologists, some proposals of revision and improvements have been suggested. At this time, I reinvestigated the Masaoka staging system based on the recent follow-up study of the thymomas resected at Nagoya City University.

METHODS

Using the follow-up results of 211 thymomas in Nagoya, I analyzed the following aspects: (1) evaluation of the Masaoka staging system as a prognostic factor in the Nagoya series and (2) critical assessment of the proposals of revision to the Masaoka staging system.

RESULTS

(1) Univariate analysis showed that Masaoka stages were significantly prognostic for overall survival (p < 0.0001). (2) The difference of survivals between stage I and II was not significant, but progression-free survival of stage I was 100% for up to 20 years, whereas one tumor death case in stage II was found. (3) Differences of survival between the cases with and without great vessel invasion in stage III were not significant. (4) Prognosis of N tumors was yet better defined.

CONCLUSION

(1) The Masaoka staging system remains a valuable prognostic factor. (2) Combination of stage I with II and separation of stage III into subgroups are not recommended. (3) At the moment, it is better to include N tumors in stage IVb.

World Health Organization classification of thymomas provides significant prognostic information for selected stage III patients: evidence from an international thymoma study group

Information regarding prognosis of thymoma patients stratified by both World Health Organization classification and Masaoka staging system is very limited. Analyze 5-year survival data from a large number of thymoma patients stratified by both World Health Organization histologic type and Masaoka stage using meta-analysis. Perform power analysis to estimate the number of cases that would be needed to test the null hypothesis to a power of 80%. Five-year survival data from 905 thymoma patients treated with thymectomy at seven hospitals in America, Japan, Korea, India, Italy, and Germany. Survival data was reported as "dead" or "alive" to facilitate meta-analysis. Significant differences were detected only when comparing survival rates of thymoma patients in stages I to III with those of stage IV disease. Analysis by World Health Organization histologic type and stage yielded significant differences only in patients with thymomas A vs. B2 and A vs. B3 in stage III disease. No significant data heterogeneity was detected with funnel plots and Egger's regression test. Power analysis estimated that a study with 7077 patients is needed to evaluate the prognostic significance of all thymomas stratified by both World Health Organization histologic type and stage to a power of 80%. Selected World Health Organization histologic types are significantly associated with prognosis in stage III thymoma patients and may help select individuals benefiting from neoadjuvant therapy. Power analysis shows that studies with much larger number of patients are needed to exclude the possibility that histologic type may provide significant prognostic information in other stages of the disease.

Interobserver diagnostic variability at "moderate" agreement levels could significantly change the prognostic estimates of clinicopathologic studies: evaluation of the problem using evidence from patients with diffuse lung disease

Does interobserver diagnostic variability (IODV) influence the accuracy of prognostic estimates of clinicopathologic studies? "Best evidence" from usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP) patients was used to investigate the effects of IODV. Systematic literature review identified studies of UIP and NSIP providing "best evidence." Survival proportions from studies were compared using chi(2) and meta-analysis. Interobserver diagnostic variability was simulated in the data arbitrarily at 5% to 30% intervals. The various "diagnoses" were evaluated with kappa, and chi(2) statistics were used to evaluate the interobserver agreement and compare survival proportions. The survival proportions for UIP and NSIP patients in 7 retrospective level III studies ranged from 11% to 58% and 39% to 100%, respectively. Analysis of simulation results with kappa and chi(2) statistics showed that IODV greater than 10% resulted in significantly different survival proportion estimations. Interobserver diagnostic variability at moderate agreement levels significantly influences prognostic estimates. Evaluation and minimization of IODV in future clinicopathologic studies are indicated.

Evidence-based evaluation of the risks of malignancy predicted by thyroid fine-needle aspiration biopsies

A National Cancer Institute (NCI) "Thyroid Fine-Needle Aspiration (FNA) State of the Science Conference" recently proposed standardized nomenclature and "risks of malignancies" associated with various diagnostic categories. We evaluated the evidence levels of the data used by NCI to predict malignancy risks and whether those estimates had clinical validity in our patient population.Eight hundred seventy-nine patients underwent thyroid FNA during 2006. FNA diagnoses were translated into NCI diagnostic categories, and 2-year follow-up retrospective information was obtained. Four percentages of malignancies were calculated for each diagnostic category using follow-up information from FNA, thyroidectomy, both, and all patients as denominators. 95% confidence intervals (CI) were estimated for all proportions, and results were analyzed with chi-square statistics. "Relative risk" calculations were performed using the percentage of malignancies in the entire population under study as a denominator.Most of the studies cited by the NCI provided incomplete and variable level III evidence based mainly on surgical follow-up. Among our patients, the percentages of malignancies calculated with follow-up data from all patients as the denominator were similar to the "risk estimates" proposed by the NCI, but estimates based on surgical follow-up overestimated the probability of thyroid malignancy for patients with FNA diagnosis of "benign" and "follicular lesions of undetermined significance" (FLUS). Relative risk and 95% CI calculations suggested that the NCI classification could be simplified into three categories: "benign," "FLUS + neoplasm," and "suspicious + malignant."

Prognostic indicators after surgery for thymoma

BACKGROUND

We undertook a 20-year retrospective institutional study to investigate prognostic indicators after surgery for thymoma.

METHODS

From 1989 to 2009, 83 patients underwent surgical resection of thymoma or thymic carcinoma at our institution. Twelve of these patients were determined to have either World Health Organization type C disease or Masaoka stage IV-B disease and were excluded from analysis. The remaining 71 patients were reviewed.

RESULTS

The majority of patients in this series were female 64.7% (n=46) with an overall average age of 51.0 years. The distribution of Masaoka stages I, II, III, and IV-A was 40.8% (n=29), 19.7% (n=14), 18.3% (n=13), and 21.1% (n=15), respectively. Thirteen of the 28 (46.2%) patients who presented with stage III or IV-A disease received preoperative chemotherapy. After a mean follow-up of 66 months (range, 6 to 241 months), 54 (75.3%) patients are alive and well while six are alive with disease. Eleven (16.0%) patients have died, but only 3 (4.3%) of these patients died of thymoma. The overall disease-specific survival was 97% and 89% at 5 and 10 years. Of the variables analyzed, only age was predictive of overall survival (p=0.03). Masaoka stages I to III as compared with stage IV-A was significantly predictive of disease-free survival (p<0.01).

CONCLUSIONS

Long-term disease-specific survival can be expected not only after surgery for early stage thymoma but also after surgery for advanced disease, including patients with pleural metastases. However, patients who undergo surgery for stage IV-A disease have reduced disease-free survival. Late mortality due to secondary cancers and associated immunologic disorders was more frequent than mortality from thymoma in this series.

Immunohistochemical detection of p63 and XIAP in thymic hyperplasia and thymomas

We subjected 23 formalin-fixed, paraffin-embedded tissue blocks (11 cases of thymic hyperplasia and 12 thymomas [3 encapsulated, 8 with capsular invasion, and 1 atypical]) to incubation with monoclonal anti-X-linked inhibitor of apoptosis protein (XIAP) (BD Biosciences, San Jose, CA) and monoclonal anti-p63 (4A4, Santa Cruz, Santa Cruz, CA). Granular or heterogeneous cytoplasmic XIAP staining and nuclear p63 staining were considered positive. We compared thymic hyperplasia with thymoma and capsulated thymoma with thymoma with capsular invasion or atypia. p63 was positive in virtually all thymic epithelial cells in hyperplasia and thymoma. XIAP was negative in all hyperplasia cases except one. Of 12 thymomas, 9 were XIAP+ with focal/weak to diffuse/strong positivity: 2 of 3 encapsulated and 7 of 8 thymomas with capsular invasion were XIAP+. One atypical thymoma was XIAP-. XIAP expression differed significantly between hyperplasia and thymoma (P = .0007) but not between capsulated and invasive thymomas (P = .3797). p63 is consistently positive in nonneoplastic and neoplastic thymic epithelium. XIAP expression in thymoma suggests a possible role in the pathogenesis of thymoma and may be helpful in differentiating thymic hyperplasia from thymoma, especially in small biopsy specimens. However, the level of expression does not correlate with capsular invasion or atypia.

Evidence-based criteria to help distinguish metastatic breast cancer from primary lung adenocarcinoma on thoracic frozen section

The distinction between primary lung adenocarcinoma and metastatic breast carcinoma in patients with a history of breast cancer is difficult by frozen section (FS) analysis. Our experience with 129 FSs from 121 patients with a pulmonary nodule and a history of breast cancer was reviewed. The pretest odds ratio of primary pulmonary carcinoma/metastatic breast carcinoma was 2.6. The incidence of 12 histopathologic features was assessed in a "training set" composed of 20 FSs, 10 with primary lung adenocarcinoma and 10 with metastatic breast cancer. A differential diagnosis model composed of significant pathologic features that favor the diagnosis of primary lung adenocarcinoma (acini, lepidic growth, nuclear pseudoinclusions, and scar) or metastatic breast carcinoma (comedonecrosis, solid nests, trabecular architecture, and cribriform growth) was identified. The external validity of this model was successfully tested by challenging 19 pathologists and trainees with a test set of 20 unknown FSs, supporting the clinical applicability of the diagnostic model.