Interobserver variation in the classification of thymic tumours--a multicentre study using the WHO classification system.

Department of Pathology, Leeds Teaching Hospital NHS Trust, Leeds, UK.
Histopathology (Impact Factor: 3.3). 09/2008; 53(2):218-23. DOI: 10.1111/j.1365-2559.2008.03088.x
Source: PubMed

ABSTRACT To test the reproducibility of the current World Health Organization (WHO) classification of thymic epithelial tumours and to determine the level of interobserver variation within a group of pathologists, all with experience and expertise in thoracic pathology.
Ninety-five thymic tumours were circulated to a group of 17 pathologists in the UK and The Netherlands over a 1-year period. Participants were asked to classify them according to WHO criteria. The diagnoses were subjected to statistical analysis and kappa values calculated. The overall level of agreement was moderate (kappa 0.45). When the categories were reduced in number by creating two groups, (A + AB + B1 + B2 and B3 + C), the level of agreement increased to 0.62. An alternative grouping (A + AB + B1 and B2 + B3 + C) increased it slightly further. The best agreement was in tumour types A and AB. Difficulties arose in distinguishing B1 tumours from B2 tumours and B2 tumours from B3 tumours.
Although the WHO system describes a number of well-defined tumour types with clear diagnostic criteria, the overall level of agreement was moderate and improved if some groups were amalgamated.

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    • "Thus, from type A to type C, there is a clear deterioration of prognosis; A, AB, B1 and B2 show a progressively worse outcome; B3 (the old 'well-differentiated thymic carcinoma') is more aggressive and shows intermediate survival, while patients with type C lesions present the worse outcome, with poor survival and high recurrence rate. Although the WHO system describes a number of welldefined tumour types with clear diagnostic criteria, the overall level of agreement is moderate with recognised intraand inter-observer discrepancies [64]; however, it could be improved if some groups are amalgamated. A meta-analysis "
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    ABSTRACT: Thymoma and thymic carcinoma are an extremely heterogeneous group of neoplastic lesions with an exceedingly wide spectrum of morphologic appearances. They show different presentations with a variable and unpredictable evolution ranging from an indolent non-invasive attitude to a highly infiltrative and metastasising one. Prognosis can be predicted on the basis of a number of variables, mainly staging, the WHO histological pattern and diameter of the tumour. Complete surgical resection is certainly the gold standard to achieve cure. However, especially in patients with lesions at advanced stage, complete resection may be difficult and recurrence often occurs; at these stages, disease-free long-term survival may be difficult to be accomplished. Chemo- and radiotherapy protocols have been designed to complete surgical treatment and improve results in inoperable patients as well, based on the reported sensitivity of thymic tumours to these treatment modalities. The integration of clinical staging and histology, with the new histogenetic morphological classification, has contributed to design multimodality treatment protocols that help to improve prognosis. Induction therapy can now be applied before surgery in patients with tumours considered inoperable, improving resectability and outcome without adding morbidity and mortality to the surgical procedure. This newly developed approach helps to reduce the recurrence rate and to ameliorate disease-free survival. New therapies are now being evaluated as for many other tumours; however, they still need confirmation in prospective randomised studies. In the future, integrated treatment modality should be incorporated in a standardised approach that goes from a careful assessment of histology, staging and lymph node status, and a constructive and non-empirical co-operation between medical and radiation oncologists, pathologists and thoracic surgeons.
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