Observer variation in the histopathological classification of thymoma: correlation with prognosis

Prognostic factors and outcome in cats with thymic epithelial tumours: 64 cases (1999-2021)

OBJECTIVES

To describe the clinical presentation, treatment and outcomes of cats diagnosed with thymic epithelial tumours and to determine prognostic factors for survival and recurrence.

MATERIALS AND METHODS

Clinical records of cats diagnosed with a thymic epithelial tumour between 1999 and 2021 at three referral institutions were retrospectively reviewed.

RESULTS

Sixty-four cats were included. Paraneoplastic syndromes were present in nine cats and metastatic disease was seen in two cats, one at diagnosis and one at the time of recurrence. Median tumour diameter was 6 cm (range, 2 to 15) and a cystic appearance was described on imaging in 25 cats. Surgical excision was attempted in 54 cats with a perioperative mortality rate of 11%. Median survival time for cats surviving to hospital discharge was 897 days (range, 21 to 3322). The 1-, 2- and 5-year survival rates for surgically treated thymic epithelial tumour were 86%, 70% and 66%, respectively. Survival was longer for cats with Masaoka-Koga stage I and II tumours compared to stages III and IV (1366 days versus 454 days; P=0.002). Masaoka-Koga stage was the only significant prognostic factor detected on multi-variable analysis, with stage III and IV tumours associated with increased risk of death (hazard ratio: 5.67, 95% confidence interval: 1.29 to 24.91, P=.021). Tumour recurrence occurred in 11 cats at a median of 564 days (range, 93 to 1095); no significant prognostic factors for recurrence were identified.

CLINICAL SIGNIFICANCE

Cats with thymic epithelial tumours had a good long-term prognosis following surgery. Tumour recurrence can occur late in the disease course and ongoing monitoring should therefore be considered. Masaoka-Koga stage may influence survival time and could be used to predict outcome.

The impact of thymoma histotype on prognosis in a worldwide database

INTRODUCTION

The rarity of thymomas and lack of multi-institutional studies have hampered therapeutic progress for decades. To overcome this, the members of the International Thymic Malignancy Interest Group created a worldwide retrospective database. This database was analyzed regarding the demographic and geographic distribution of thymomas and the impact of different variables on survival and recurrence.

METHODS

This study analyzed 4221 thymomas diagnosed between 1983 and 2012 with World Health Organization histotype information from the International Thymic Malignancy Interest Group database. Associations to survival and recurrence were studied by univariate and multivariate analyses.

RESULTS

Type B2 thymoma is the most common (28%) and type A the least common (12%) histotypes. They are significantly more frequent in Europe and the United States than Asia. Type A and AB occur at significantly higher age than other thymomas (64 and 57 years, respectively). There are no differences in gender distribution. Stage is lower in type A (90% in stages I-II) and AB than B1 to B3 thymomas (38% of type B3 in stage III). In univariate analysis, recurrence is significantly less frequent among stage I/II tumors, in type A and AB (recurrence rates, 1-2%) than B1 to B3 thymomas (2-7%). Multivariate analysis reveals an impact of age, stage, and resection status on survival and recurrence, whereas for histology there is only a significant impact on recurrence.

CONCLUSION

New findings are (1) geographic differences such as a lower incidence of type A and B2 thymoma in Asia; and (2) impact of stage and histology, the latter partially limited to early stage disease, on recurrence.

Invasive thymoma metastatic to the cavernous sinus

Background:

Thymomas are typically benign tumors of thymic epithelium. Metastases to distal sites, particularly intracranial locations, are extremely rare. Herein, we present the third case of thymoma and the second invasive thymoma to metastasize to the cavernous sinus, adjacent to the pituitary.

Case Description:

A 41-year-old female patient presented with headaches, stuffy nose, and drooping of the right face. A magnetic resonance imaging scan revealed a complex, multilobulated mass centered upon the right cavernous sinus. The mass was removed via transsphenoidal surgery, and histopathological investigation confirmed the diagnosis of metastatic thymoma. A positron emission tomography-computed tomography scan demonstrated a large anterior mediastinal mass. A biopsy confirmed the diagnosis of invasive thymoma morphologically identical to the World Health Organization type B2 sellar region metastasis.

Conclusion:

Although rare, thymomas can metastasize to the central nervous system. Our case is the second invasive thymoma to metastasize to the cavernous sinus, adjacent to the pituitary.

Management of stage I and II thymoma

With a knowledgeable assessment of the clinical presentation and demographic and radiologic characteristics, most thymomas can be reliably identified preoperatively without the need for a biopsy. Surgery is the mainstay of treatment for stage I and II thymoma. The rate of complete resection is essentially 100% by open techniques, and recurrences are rare. A complete thymectomy via a sternotomy is the standard approach. Adjuvant radiotherapy after a complete resection does not appear to be of benefit. In the rare event of a recurrence, an aggressive approach should be taken with re-resection whenever possible.

Invasive spindle cell thymomas (WHO Type A): a clinicopathologic correlation of 41 cases

We report 41 cases of invasive spindle cell thymomas (World Health Organization type A). The patients were 16 women and 25 men between the ages of 38 and 80 years. Clinically, the patients had diverse symptomatology, including chest pain, cough, and dyspnea. None of the patients had a history of myasthenia gravis. According to the Mazaoka surgical staging system, 34 patients had stage II disease, 6 had stage III, and 1 had stage IV. Follow-up information showed that 30 patients were alive after a period ranging from 12 to 96 months; for 8 patients who are alive, the follow-up was less than 12 months; 1 patient died 10 months after initial diagnosis. For 2 patients, no follow-up information was obtained. This study stresses the fact that histologic features do not correlate with invasion or encapsulation because all thymomas, regardless of their histologic type, are capable of invasion.

The role of a pseudocapsula in thymic epithelial tumors: outcome and correlation with established prognostic parameters. Results of a 20-year single centre retrospective analysis

BACKGROUND

Treatment of thymoma is often based on observation of only a few patients. Surgical resection is considered to be the most important step. Role of a pseudocapsula for surgery, its clinical significance and outcome compared with established prognostic parameters is discussed which has not been reported so far.

METHODS

84 patients with thymoma underwent resection and analysis was carried out for clinical features, prognostic factors and long-term survival.

RESULTS

Fifteen patients were classified in WHO subgroup A, 21 in AB, 29 in B and 19 patients in C. Forty two patients were classified in Masaoka stage I, 19 stage II, 9 stage III and 14 stage IV. Encapsulated thymoma was seen in 40, incomplete or missing capsula in 44 patients. In 71 complete resections, local recurrence was 5%. 5-year survival was 88.1%. Thymomas with pseudocapsula showed a significant better survival (94.9% vs. 61.1%, respectively) (p = 0.001) and was correlated with the absence of nodal or distant metastasis (p = 0.04 and 0.001, respectively). Presence of pseudocapsula as well as the Masaoka and WHO classification, and R-status were of prognostic significance. R-status and Masaoka stage appeared to be of independent prognostic significance in multivariate analysis.

CONCLUSION

Intraoperative presence of an encapsulated tumor is a good technical marker for the surgeon to evaluate resectability and estimate prognosis. Although the presence of a capsula is of strong significance in the univariate analysis, it failed in the multivariate analysis due to its correlation with clinical Masaoka stage. Masaoka stage has a stronger relevance than WHO classification to determinate long-term outcome.

Clinical value of the WHO classification system of thymoma

Since the World Health Organization (WHO) histologic classification system for thymoma was introduced in 1999, several centers have published results using this system. This review of the published experience with the WHO system examines whether the classification is reproducible, whether the WHO system defines clinically distinct patient groups, assesses the independent prognostic value of the WHO type by multivariate analysis, and discusses the impact of the WHO system on clinical management decisions.

Problem areas and inconsistencies in the WHO classification of thymoma

The morphologic classification of thymoma has undergone numerous revisions in recent years and has been under continuous debate for the past several decades. With the introduction of the World Health Organization (WHO) schema for the classification of thymic epithelial neoplasms in 1999, a major step was taken toward achieving uniformity in the nomenclature of these tumors. A more recent iteration of the WHO morphologic classification of thymic epithelial neoplasms has now been published. Although these efforts have certainly contributed to clarifying many issues related to the pathology of thymoma, several problem areas and inconsistencies still remain surrounding this proposed schema. The purpose of this review is to address these problem areas, in particular as it relates to terminology, histopathologic criteria for diagnosis, and the prognostic significance for the various categories of the WHO schema.

Proposal of a Novel System for the Staging of Thymic Epithelial Tumors

BACKGROUND

We designed and assessed a new TNM staging system (herein called the INT [Istituto Nazionale Tumori] system) for thymic epithelial tumors in order to overcome the perceived drawbacks of Masaoka's system, which represents the current standard.

METHODS

In all, 123 cases were evaluated. The histologic types according to the World Health Organization (WHO) classification were as follows: subtype A: 5 cases; AB: 40; B1: 16; B2: 29; B3: 16; and C: 17 cases. There were 45 Masaoka's stage I, 33 stage II, 26 stage III, and 19 stage IV cases. A total of 11 INT definitions were grouped into three stages: locally restricted disease (75 cases), which included Masaoka's stage I and selected stage II cases (no pleural invasion); locally advanced disease (37 cases), which included Masaoka's stage III cases plus those staged II owing to pleural invasion and those staged IV owing to intrathoracic nodal or limited pleuropericardial involvement; and systemic disease (11 cases), which included the remaining Masaoka's stage IV cases.

RESULTS

Completeness of resection, WHO types, and both staging systems were significant prognostic factors (p < 0.0001) on univariate analysis. The 95-month progression-free survival rates according to Masaoka's system were stage I: 100%; II: 93.6%; III: 46.3%; and IV: 23.2%. The INT system corresponding figures were as follows: locally restricted disease: 98.6%; locally advanced disease: 46.9%; and systemic disease: 11.7%. The INT system was the prognostic factor with the greatest impact (p = 0.0218) on multivariate analysis (Masaoka's system: p = 0.2012; completeness of resection: p = 0.6855; histology: p = 0.9386).

CONCLUSIONS

The INT system allows finer disease descriptions than Masaoka's system, resulting in a stage grouping with higher prognostic distinctiveness.

Prognostic and Clinical Relevance of the World Health Organization Schema for the Classification of Thymic Epithelial Tumors

STUDY OBJECTIVES

Controversy has ensued about the prognostic relevance of the new World Health Organization (WHO) schema for the classification of thymoma. In this study, we present the clinical and histologic features of 108 thymomas and evaluate the usefulness of this histologic schema in view of the prognosis.

DESIGN

Retrospective, clinicopathologic analysis of our experience and a review of recent literature.

SETTING

Department of Thoracic and Cardiovascular Surgery of a university hospital.

METHODS

A series of 108 thymomas were reviewed and classified by the new WHO schema. The clinical characteristics and the survival outcome were investigated in reference to the WHO subtypes. The Cox proportional hazards model was applied to determine the factors affecting the tumor-related survival. Recent literature on the prognostic relevance of the WHO schema was reviewed.

RESULTS

There were 7 type A tumors, 25 type AB tumors, 12 type B1 tumors, 32 type B2 tumors, 20 type B3 tumors, and 12 type C tumors. The histologic subtype closely correlated with the Masaoka stage (p = 0.00). The tumor-related survivals at 5 years and 10 years were 88.0% and 77.9%, respectively. Stage III and IV tumors had a significantly worse prognosis than stage I or II tumors (p < 0.05). Type B3 tumors had an intermediate prognostic ranking in comparison with the carcinomas and with the other groups. On multivariate analysis, the WHO subtype (A-B2 vs B3 vs C) could predict the tumor-related survival, but the Masaoka stage was the most important prognostic factor affecting the postoperative survival (p = 0.026).

CONCLUSION

The Masaoka stage is the most important determinant of survival in surgically resected cases of thymoma. To clarify the prognostic relevance and clinical usefulness of the WHO schema, consistent parameters reflecting the surgical outcome and development of the diagnostic tools that could improve the interobserver agreement within type B are needed.

Microthymoma

We report 2 cases of microscopic-sized thymoma, which probably represents the earliest phase of thymoma development. The 2 patients presented with pure red cell aplasia and myasthenia gravis, respectively. The thymectomy specimens did not reveal tumor on gross examination, but histologically each contained small thymomas measuring 5 mm and 7 mm in largest dimension, respectively. One of the tumors was unencapsulated and involved a single lobule only, and the other was encapsulated and comprised two lobules. The tumors consisted of ovoid epithelial cells with pale nuclei and distinct nucleoli, scattered in a background of small lymphocytes. Foci of medullary differentiation and perivascular space were identified in the 2 cases, respectively. The lymphocytes were confirmed to be immature T cells on immunohistochemical studies (CD3+, TdT+). Except for the microscopic size, the morphology of the two tumors conforms to conventional type B1/B2 and type B2 thymoma, respectively. We propose calling such incidental small tumor "microthymoma" to distinguish it from the so-called microscopic thymoma, which is composed of small thymic epithelial nests and probably more appropriately termed "nodular hyperplasia" of the thymic epithelium.

Haemorrhagic brain metastasis from a thymic carcinoma

Brain metastasis from thymic carcinoma is extremely rare, and there is still no consensus regarding the best management of thymic metastasis to the central nervous system. Here, we report the first-known Australian case. A review of the current literature and the characteristics of thymic tumours with brain metastasis indicate that aggressive management may be able to improve long-term outcomes for these patients. A 49-year-old man presented 2 weeks after thoracotomy for thymic carcinoma resection with a 2-day history of headache, right-sided weakness and expressive dysphasia. CT and MR scans revealed two metastatic brain lesions, one within the left frontal lobe with cystic necrosis and haemorrhage, the other deep in the parietal lobe adjacent to the left ventricle with a lesser degree of haemorrhage. The patient underwent frameless stereotactic craniotomy for excision of the frontal lesion. Histopathology confirmed poorly differentiated thymic carcinoma. Post-operatively his weakness and speech improved dramatically, and he was discharged home within a week, with radiotherapy and chemotherapy to follow. However, he represented with rapidly worsening symptoms and died within a week. Thymic carcinoma is a rare tumour, displaying malignant features clinically and histopathologically with local invasion to adjacent organs. Metastasis is predominantly to lung, bone, liver and kidney, with less predilection for the central nervous system. Treatment for thymic carcinoma is multimodal, but outcome remains poor and life expectancy is very short when brain metastasis with haemorrhage is present.

Interobserver variation in histopathological assessment of Helicobacter pylori gastritis

AIM

Because the presence or absence of H pylori infection has important implications for therapeutic decisions based on histological assessment, the reproducibility of Sydney system is important. The study was designed to test the reproducibility of features of Helicobacter pylori gastritis, using the updated Sydney classification.

METHODS

Gastric biopsies of 40 randomly selected cases of H pylori gastritis were scored semiquantitatively by three pathologists. Variables analysed included chronic inflammation, inflammatory activity, atrophy, intestinal metaplasia, H pylori, surface epithelial damage. Kappa values below 0.5 represented poor, those between 0.5 and 0.75 good and values over 0.75 excellent interobserver agreement.

RESULTS

The best interobserver agreement (kappa=0.62) was present for intestinal metaplasia. The agreement was the poorest for evaluating atrophy (kappa=0.31).

CONCLUSION

Although the results of this study were in accordance with some previous studies, an excellent agreement could not be reached for any features of H pylori gastritis. This low degree of concordance is assumed to be due to the personal evaluation differences in grading the features, the lack of standardized diagnostic criteria, and the ignorance to reach a consensus about the methods to be used in grading the features of H pylori gastritis before initiating the study.

Thymoma: a review of the clinical and pathological findings in 65 cases

INTRODUCTION

Although rare, thymoma is the most common tumour of the anterior mediastinum. In an effort to assess the clinical and pathologic characteristics of this tumour and to determine whether clinicopathologic stage or histopathologic classification correlates with clinical outcome, in the Department of Pathology and the Department of Surgery at the University of Saskatchewan we reviewed all cases of thymoma registered in the province of Saskatchewan using the database of the Saskatchewan Cancer Centre.

METHODS

In 65 patients with a diagnosis of thymoma or thymic carcinoma identified from the Saskatchewan Cancer Centre database between Jan. 1, 1960, and Dec. 31, 2000, we studied the presentation, diagnostic investigations, therapeutic interventions, tumour size, postoperative course, clinical stage, histopathologic classification, disease recurrence and mortality.

RESULTS

Of the 65 patients, 17 (26%) were asymptomatic and 11 (17%) had symptoms consistent with myasthenia gravis. Surgical resection is most commonly performed through a median sternotomy and frequently requires en bloc resection of one or more adjacent structures. The overall survival of patients with thymomawas found to correlate with the clinical stage as described by Masaoka and colleagues and with complete tumour resection. A trend to clinicopathologic correlation was observed when applying the histologic classification systems of Suster and Moran and the World Health Organisation, but this trend was not statistically significant.

CONCLUSIONS

Thymoma is a rare tumour with a variable clinical presentation. Clinical outcome correlates with clinical stage and the ability to achieve complete tumour resection.

Correlation of the WHO schema for the classification of thymic epithelial neoplasms with prognosis: a retrospective study of 90 tumors

A series of 90 thymic epithelial tumors were reviewed and classified by histopathologic characteristics into the three major categories (A, B, and C) recognized by the WHO schema. Each tumor type was correlated with patient characteristics and clinical data (age, sex, presence of myasthenia gravis, tumor size and invasiveness, and completeness of resection), and with outcome (survival, recurrence, and metastasis). All tumors were categorized by the WHO schema. Myasthenia gravis was present in 32 patients, mostly young and with type B thymic epithelial tumors. Tumors were invasive in 56% of cases, but resection was total in 67% of patients and only partial in the rest. Five factors were shown by univariate analysis to be associated with a favorable prognosis: presence of myasthenia gravis (p = 0.0389), younger age (p = 0.0022), completeness of resection (p = 0.0001), noninvasiveness (p = 0.0138), and tumor type A or B, as opposed to type C (p = 0.0001). Prognosis for types A and B was not significantly different, suggesting that the subtypes of types A and B thymic epithelial tumors should be regarded as a morphologic continuum rather than as distinct histologic variants.

Histologic classification of thymic epithelial tumors: comparison of established classification schemes

The object of our multicenter retrospective study was to compare the new histologic World Health Organization (WHO) classification and the classical histologic Bernatz classification in terms of interobserver agreement and prognostic importance. The influence of coexisting diseases was also analyzed using the Charlson score. We evaluated 218 patients from 5 different hospitals who were treated between 1967 and 1998. The statistical methods of analysis included Kaplan-Meier estimates of survival curves and the application of Cox proportional hazards models to identify sets of prognostic factors for survival. Interobserver agreement was assessed by kappa coefficients. For both WHO and Bernatz classifications, interobserver agreement was good (weighted kappa > 0.87). However, the subdiversification of the "bioactive" WHO subgroup (B1, B2, B3) resulted in an interobserver agreement of only 0.49 within this group. In multivariable models, both the WHO classification and the Bernatz classification including carcinomas showed similar prognostic capabilities. The B3 type in the WHO classification and the predominantly epithelial type in the Bernatz classification had an intermediate prognostic ranking in comparison with the carcinomas and with the other subgroups. For both classifications, further simplification and subclassification into 3 subgroups led to classes with good discriminative power in respect to survival. In addition, very good interobserver agreement was observed in the simplified classifications. Comorbidity, sex, age of the patient and lymphofollicular hyperplasia had no major influence on overall survival. Both classifications showed similar prognostic power. Interobserver agreement of the type B subgroups was only moderate. By simplification of the classifications, subgroups with distinct survival could be identified.

Thymoma: trends over time

BACKGROUND

This is a review of a series of patients who presented with thymoma over the most recent 20-year period. Changes and trends in disease patterns were documented.

METHODS

Data were collated retrospectively but all pathology slides were reviewed. Survival functions were estimated using the Kaplan-Meier method.

RESULTS

Seventy-one patients had a partial or total thymectomy during this period for a thymoma. Average age was 55 years. Twenty-three patients (32%) had myaesthenia gravis. Eighteen patients (25%) were asymptomatic. Thirty-three patients (47%) had stage 1 disease. Complete resection was achieved in 60 patients (85%). Five-year survival was 88%. Fifty percent of patients with myesthenia gravis showed improvement in symptoms.

CONCLUSIONS

Five- and 10-year survival rates in this study are better than in other series. We attribute this to an increasing number of patients with stage 1 and stage 2 disease, particularly those with myasthenia gravis who now have screening computer tomography, and also to the surgical intent of aiming to achieve complete resection even if excision of adjacent tissue is required.

Thymic malignancies

Thymomas and thymic carcinomas are unique tumors of the anterior mediastinum. The association of a variety of different paraneoplastic syndromes with such lesions has fascinated physicians and researchers for years. Most recently, it has been demonstrated by numerous authors that thymomas are chemosensitive tumors. Their indolent nature and relative rarity have made evaluation through prospective randomized clinical trials extremely difficult. Further information regarding the molecular nature of these neoplasms and immunologic aspects is needed in future investigation.

Current status of the diagnosis and treatment of thymoma

Although thymomas are rare neoplasms, they are the most common tumor of the anterior mediastinum in adults. Preferred therapy for these neoplasms is complete surgical resection. If a thymoma cannot be completely resected, postoperative radiotherapy may produce satisfactory results in controlling the tumor. Significant 5- and 10-year survival rates have been recorded for patients with advanced thymomas who have been treated by radiation therapy alone. Chemotherapy may be used in patients with unresectable thymomas as well, but the results are less promising than with radiotherapy. Combinations of radiotherapy and chemotherapy used on patients with unresectable thymomas have produced encouraging results. Surveillance of patients with thymoma should be prolonged because late recurrence (more than 5 years after initial therapy) can be expected in a significant minority of patients. Aggressive therapy of late recurrence, including resection of new tumor masses and pleural metastases, has yielded successive disease-free intervals that validate persistent treatment.

Histologic estimation of coronary artery stenoses: reproducibility and the effect of training

Histologic estimation of coronary artery stenoses (CAS) provides the 'gold-standard' for clinicopathologic correlations and medicolegal investigations, yet little evidence supports histology as a reproducible diagnostic measure, and none addresses the effect of training on its use. To study these questions, 20 randomly selected Movat-stained coronary artery cross-sections were reviewed 3 times, at 3-month intervals, by six clinical pathologists (CPs), six pathology residents (Res), seven anatomic pathologists (APs), and two cardiovascular pathologists (CVPs). Before the third iteration, a guide to CAS assessment with illustrations was provided. Inter- and intraobserver reproducibility were determined using interclass correlation coefficients (ICC) (0.40-0.75 = fair-good; > or = 0.76 = excellent agreement beyond chance). Surprisingly, all study groups had excellent interobserver reproducibility. Before training, at Time 1, the scores were CPs, 0.77; Res, 0.89; APs, 0.93; and CVPs, 0.93. After training, at Time 3, the results were CPs, 0.81; Res, 0.91; APs, 0.86; and CVPs, 0.88. Intraobserver reproducibility for CPs overall was good (ICC, 0.74), and excellent for Res, APs, and CVPs (0.89, 0.94, and 0.97, respectively). In conclusion, statistical analysis failed to demonstrate any significant effect of training or experience on observer reproducibility.

Thymic tumours in Denmark. A retrospective study of 213 cases from 1970-1993

Histological slides of 213 thymic tumours were reviewed twice and classified according to Kirchner and Müller-Hermelink into 122 thymomas (syn. organotypic thymic epithelial tumours (TET)), 58 thymic carcinomas (syn. non-organotypic TET) and 16 lymphomas. Tumour heterogeneity (i.e. features of two subtypes in one tumour) appeared in 38% of the organotypic TET. The overall diagnostic correspondence between the reviews of the 122 organotypic TET was 48%. By reducing the five diagnostic groups to three: organotypic TET benign (medullary and mixed thymomas), organotypic TET low-grade (organoid and cortical thymomas and well-differentiated thymic carcinoma (WDTC)) and non-organotypic TET (usually high-grade thymic carcinomas), and minimising the effect of tumour heterogeneity in this way, the diagnostic correspondence increased to 82%. Correlating histological type with stage, we found that 80% of medullary and 87% of mixed thymomas were stage I, that 85% of cortical and 81% of WDTC were stage II or III, and that non-organotypic TET were stage II or III (86%) or stage IV (14%), respectively. It is suggested to report on the heterogeneity of a given case of thymic epithelial tumour in the pathology reports and give the approximate percentage of each component, telling the clinician which component may determine the prognosis.

Thymoma: state of the art

Thymoma is the most common tumor of the anterior mediastinum. This tumor is associated with unique paraneoplastic syndromes, such as myasthenia gravis, hypogammaglobulinemia, and pure red cell aplasia. The rarity of this tumor, however, has somewhat obscured the optimal treatment for this disease. For the majority of patients who present with localized tumor, surgical extirpation remains the standard of choice. Adjuvant radiotherapy seems to improve local control and survival. In more advanced disease, systemic therapy has been demonstrated to produce a 50% to 80% objective response rate. These observations have led to the development of multimodality therapy for the treatment of patients with advanced thymoma. In this article, we will review the current perspectives on the management of early stage and advanced thymoma.

Controversies in the management of malignant thymoma

The management of most thymomas is relatively straightforward: surgical resection remains the primary mode of therapy. However, the literature contains many contradictory points of view regarding histology and pathology, staging and its usefulness, the need for adjuvant therapy, and recently, the place of video-assisted surgery in the treatment of this tumor. This article is not a comprehensive guide to management but rather explores several of these controversial areas. Conclusions include the following: invasiveness remains the single most consistent factor in predicting outcome; surgery is the treatment of choice for thymoma whenever a complete resection can be accomplished; and incomplete resection may have some advantage over biopsy alone. The preponderance of evidence indicates that all thymomas except completely encapsulated stage I tumors should be treated with postoperative adjuvant radiation therapy in the hope of reducing the incidence of local relapse. Myasthenia can no longer be considered an adverse prognostic factor in thymoma; it may even confer a survival advantage, but this may be due to the preponderance of early-stage tumors discovered incidentally in myasthenic patients. Other associated autoimmune diseases confer a survival disadvantage. Demonstrating the equivalence of minimally invasive thoracoscopic approaches to standard thymectomy will take many years of investigation. Some promising reports on response to chemotherapy have led to the development of a phase II intergroup study to assess the value of chemotherapy in advanced thymoma.

Interobserver variation in the histopathological assessment of Helicobacter pylori gastritis

The histopathologic detection of Helicobacter pylori in gastric biopsy specimens is considered the gold standard for the diagnosis of H pylori infection. However, few studies have addressed the pathologists' reliability to detect the organism and to assess the degree of the related inflammatory changes. The objectives of this study were to determine the degree of agreement among the findings of four gastrointestinal pathologists in the semiquantitative evaluation of H pylori infection and gastritis. Three slides from specified areas of the stomach of 99 patients with and without H pylori infection were stained with the triple stain, coded, and examined independently by four pathologists. For each specimen, a visual analogue scale graded from 0 (absent/normal) to 5 (maximal intensity) was used to score (1) H pylori (2) neutrophils, and (3) atrophy. Data were analyzed using kappa-statistics. The kappa-coefficient for the detection of H pylori (present vs absent) was approximately .9 (excellent); for the intensity of infection, it was considerably lower on the 6-point scale (approximately .61) and improved slightly on an amalgamated 4-point scale (approximately .71). The agreement on presence or absence of neutrophils was excellent (kappa = .8) in antral biopsies and good (kappa = .67) in corpus biopsies. The kappa for the semiquantitative scoring of neutrophils was poor on the 6-point scale (approximately .43) and fair on the amalgamated scale (approximately .54). The interobserver agreement was the poorest in the evaluation of atrophy (presence, absence, categories, or group categories) with kappa coefficients varying from .08 and .29. This group of pathologists had a high level of concordance on the diagnosis of H pylori infection in any particular patient and a high index in the assessment of the intensity of infection. The agreement was less in the semiquantitative evaluation of active inflammation. When the evaluation concerned a loosely defined feature, such as atrophy, there was essentially no agreement among the pathologists. This study suggests the need for further assessments of pathologists' ability to provide reproducible diagnoses. These results also indicate that more stringent criteria for the diagnosis of "soft" histopathologic features (such as atrophy) are urgently needed.

Thymoma--a study of 60 cases in Singapore

Of 60 cases of thymomas studied in Singapore between 1988 and 1992, the histogenetic classification proposed by Müller-Hermelink was successfully applied to subtype 58 cases. There were 20 (33%) cortical, six (10%) predominantly cortical, three (5%) medullary and 12 (20%) mixed thymomas. Twelve (20%) cases were well differentiated thymic carcinomas and five (8%) were classified as other thymic carcinomas. The pathological and clinical features are presented in detail. These subtypes showed significant correlation with invasive behaviour (stage) and myasthenia gravis. We conclude that the Müller-Hermelink classification has predictive utility and represents a major step towards the understanding of the biology of thymic epithelial tumours.