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Chapter 38: Thymic Malignancies

Chul Kim; Giuseppe Giaccone

INTRODUCTION

Epidemiology

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Epidemiology
Incidence: 0.13 cases per 100,000 (0.2–1.5% of all malignancies) Stage at presentation: (Masaoka Staging System)
Median age: 40–60 years
Male to female ratio: 1:1 Stage I: 32%

Engels EA, Pfeiffer RM. Int J Cancer 2003;105:546–551

Schmidt-Wolf IGH et al. Ann Hematol 2003;82:69–76

Tomiak EM, Evans WK. Crit Rev Oncol Hematol 1993;15:113–124

 Stage II: 23%
Stage III: 34%
Stage IV: 11%

Pathology

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Pathology

Several histologic classifications of thymomas have been proposed. There is general agreement that the epithelial cells represent the malignant cells in this tumor type and the lymphocytic cells are considered benign

Classification of Thymic Epithelial Tumors
Muller-Hermelink WHO Type Levine and Rosai
Thymoma Thymoma Thymoma
Medullary type Type A Encapsulated
Mixed type Type AB —
Predominantly cortical Type B1 Malignant type I (invasive)
Cortical type Type B2 —
Well-differentiated carcinoma Type B3 —
Thymic carcinoma Type C Malignant type II

Levine GD, Rosai J. Hum Pathol 1978;9:495–515

Müller-Hermelink HK, Marx A. Curr Opin Oncol 2000;12:426–433

Okumura M et al. Cancer 2002;94:624–632

Work-up

  1. CT scan of the thorax

  2. Extrathoracic disease such as metastases to the kidney, bone, liver, and brain are rare. Consequently, an extensive work-up for disease outside the thorax is not indicated in the absence of symptoms

  3. Pleural or pericardial dissemination represents the most common form of metastatic involvement

  4. Proper intrathoracic staging is surgical

 

Ströbel P et al. Blood 2002;100:159–166

Thomas CR Jr et al. J Clin Oncol 1999;17:2280–2289

Five-Year Survival

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Five-Year Survival
Stage I 96–100%
Stage II 86–96%
Stage III 56–69%
Stage IV 11–50%
Schneider PM et al. Ann Surg Oncol 1997;4:46–56

Expert Opinion

  • Despite their rarity as a group of cancers, thymic epithelial tumors (TETs) are among the most common cancers of the anterior mediastinum in adults

  • The clinical course can vary from relatively indolent in the case of some thymomas to highly aggressive in the case of thymic carcinomas

  • Thymomas are often associated with a variety of autoimmune conditions; myasthenia gravis is the most common

  • Complete surgical resection should be attempted whenever feasible

  • Multimodality treatment is frequently required for locally advanced TETs

  • Chemotherapy is offered to patients with advanced stages III to IV TETs. The evidence for these recommendations is derived from small phase 2 studies in either the neoadjuvant or refractory/recurrent disease setting

  • Platinum-based combination chemotherapy is the standard of care for unresectable, advanced disease. A combination of cisplatin, doxorubicin, and cyclophosphamide (PAC) or cisplatin and etoposide (EP) are usually used as first-line regimens. More recently, the combination of carboplatin and paclitaxel has been introduced and appears to have reasonable activity in thymic carcinomas in particular1–3

  • The molecular pathogenesis of TETs is gradually being unraveled. Sunitinib demonstrated anti-tumor activity in thymic carcinomas

  • The role ...

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