Masaoka staging

Masaoka staging

A system that is used clinically to stage thymomas, and is the most important determinant of survival post surgical resection; it is comprised of four stages (the last of which contains two sub-stages):
▪ Stage I—Intact thymic capsule;
▪ Stage II—Capsular invasion into adjacent mediastinal fat or pleura;
▪ Stage III—Macroscopic invasion into adjacent organs and vessels;
▪ Stage IVa—Dissemination in thoracic cavity (i.e pleural or pericardial implants); and
▪ Stage IVb—Distant metastases.

Stage II and above are regarded as thymic carcinoma.
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In Cox regression analysis [Table 4] and [Figure 4], after controlling variables, such as sex, age, Masaoka staging, and WHO classification, the outcome is the same as that of Kaplan-Meier survival curves.{Table 4}{Figure 4}
Until the 8th edition, no consensus staging system had been agreed upon for thymic epithelial tumors, with numerous systems proposed during the past decades and the revised Masaoka staging system being the most frequently applied.
(4) The thymoma was completely encapsulated without microscopic or macroscopic invasion of the surrounding capsule, tissue, or vessels, so that according to the Masaoka staging system, which is used widely in human medicine, a benign stage was diagnosed.14 However, 1 year later, metastasis of the thymoma to the lung was identified; therefore, the initial diagnosis of a benign stage was corrected to a malignant nodular stage of an epithelioid cortical-type thymoma, according to the recently proposed classification.
The tumor at initial diagnosis presented in stage IVb according to the Masaoka staging system.
According to the Masaoka staging system [20], the present case had advanced disease with haematogenous spread to the bone marrow (stage IVb).
Table 1: World Health Organization classification of thymoma Type Histologic description A Medullary thymoma AB Mixed thymoma B1 Predominantly cortical thymoma B2 Cortical thymoma B3 Well-differentiated thymic carcinoma C Thymic carcinoma Table 2: Masaoka staging system of thymoma Stage 1 Encapsulated tumor with no gross or microscopic invasion Stage 2 Macroscopic invasion into mediastinal fat or pleura Stage 3 Invasion of pericardium, great vessels, or lung Stage 4 Pleural or pericardial metastatic spread Stage 5 Lymphatic or hematogenous spread
In this study, the Masaoka staging system of thymoma was used for the classification of thymic neoplasms.
Thymoma: interrelationships among World Health Organization histology, Masaoka staging and myasthenia gravis and their independent prognostic significance: a single-centre experience.
We have discussed the various histological classifications for thymomas as well as the widely accepted postsurgical Masaoka staging, which is an independent predictor of outcome and survival.
In 1994, Koga et al (33) modified the Masaoka staging, changing invasion into the tumor capsule (Masaoka stage II/2) to microscopic invasion through the capsule (transcapsular; Koga stage IIA) to accommodate the most common point of view of pathologists that a tumor is invasive if it grows through the tumor capsule (Table 6).
The mainstay of treatment for thymomas is surgery for complete removal of the tumor, (7,8) which may be followed by adjuvant radiation or hormone therapy/chemotherapy depending on the histologic type (WHO classification) and the stage of the tumor (Masaoka staging system).
This was done because Masaoka staging alone can miss the true oncologic implications of thymoma; in fact, recurrence may appear in a fairly great percentage of patients with early stage thymoma.