Mediastinum
Cytopathology Competency Assessment
Thymus

Author: Gordon H. Yu, M.D. (see Authors page)

Revised: 28 April 2016, last major update September 2012

Copyright: (c) 2003-2016, PathologyOutlines.com, Inc.

Cite this page: Cytology/Competency Assessment - Thymus. PathologyOutlines.com website. http://pathologyoutlines.com/topic/mdstnmcytcompthymus.html. Accessed March 24th, 2017.
Medical Knowledge, Practice Based Learning and Systems Based Practice
  1. Understand anatomic features of the thymus gland and its normal histology
  2. Understand the embryologic development of the thymus and its physiologic role
  3. Understand the normal evolution of the thymus gland as the normal adult ages
  4. Recognize the broad range of diseases which may involve the thymus gland and the incidence of thymic neoplasia
    1. Thymic Hyperplasia
      1. Follicular hyperplasia
        • Recognize the histologic features of follicular hyperplasia and its associated conditions (primarily autoimmune diseases)
      2. True hyperplasia
        • Understand the definition of true hyperplasia
        • Recognize the age range in which true hyperplasia most commonly occurs and its differentiation from “rebound” hyperplasia in adults
        • Recognize the FNA findings of true hyperplasia and understand the difficulty in separating this entity from thymoma on the basis of cytologic findings alone
    2. Thymoma
      1. Learn the incidence of thymoma and its histologic features
      2. Identify its expected anatomic location (compartment) within the mediastinum as well as other possible locations, based on the embryologic development of the thymus
      3. Recognize the age range of patients with thymoma and possible associated clinical findings due to mechanical compression and paraneoplastic syndromes
      4. Become familiar with the classification systems for thymoma and the histologic differences between different tumor subtypes within each system
      5. Identify histologic subtypes which are associated with aggressive clinical behavior and poor prognosis
      6. FNA features of thymoma
        • Recognize typical cytologic features encountered in FNA of thymoma
        • Identify immunohistochemical stains which may be of use in the diagnosis of thymoma, provided cell block material is available
        • Become familiar with cytologic features which allow the recognition of lesional cells as lymphoid, epithelial, epithelioid (cortical) and spindle (medullary)
        • Recognize the difficulty of precise subclassification of thymomas on the basis of cytomorphology alone
      7. Become familiar with the differential diagnosis of mediastinal lesions containing both lymphoid and epithelial cells, including thymic carcinoid, germ cell tumors, Castleman disease and lymphoma
      8. Recognize helpful cytomorphologic features which may allow the distinction of thymoma from other potential mediastinal lesions, as well as the role of immunohistochemical stains when adequate cell block material is available
    3. Invasive Thymoma
      1. Recognize histologic features which define the diagnosis of invasive thymoma
      2. Recognize cytologic features observed in FNA material which may be more commonly associated with invasive thymoma
      3. Recognize that the critical morphologic features diagnostic of invasive thymoma cannot be identified or excluded on the basis of cytomorphology alone
    4. Thymic Carcinoma
      1. Identify the age range of patients with thymic carcinoma as well as typical signs and symptoms associated with this tumor
      2. Recognize the cytomorphologic features seen in FNA of thymic carcinoma and its differential diagnosis
      3. Recognize the use of immunohistochemical stains in the differential diagnosis of thymic carcinoma (i.e. cytokeratin, CD5, CD70, CD117)
    5. Paraneoplastic associations with Thymic Disease
      1. Recognize the frequent association of thymic disease (including follicular hyperplasia and thymoma) with myasthenia gravis
      2. Recognize the proposed pathogenesis of myasthenia gravis as it relates to thymoma, and the expected clinical course of neurologic symptoms following thymectomy
      3. Recognize the incidence of development of myasthenia gravis in patients with thymoma, and vice versa
      4. Recognize the most frequent subtype of thymoma seen in patients with myasthenia gravis
      5. Identify other conditions which have been observed in association with thymic diseases (hypogammaglobulinemia, erythroid hypoplasia, connective tissue diseases)
    6. Thymic Neuroendocrine Tumors
      1. Carcinoid tumors
        • Identify the typical patient population and clinical presentation of carcinoid tumor of the mediastinum
        • Recognize expected FNA findings of carcinoid in Romanowsky and Papanicolaou stained preparations
        • Recognize the differential diagnosis of carcinoid and the utility of immunohistochemical staining
      2. Small cell carcinoma
        • Recognize the typical cytologic features of small cell carcinoma, its similarity to those occurring in the lung and its differential diagnosis
      3. Large cell neuroendocrine carcinoma
        • Recognize the rarity of this tumor in the mediastinum and its differential diagnosis