Lymphomas Involving the Thymus

Definition

• A small number of lymphomas appear to have a propensity to arise in or involve the thymus

Diagnostic Criteria

• Follow links for full description of types of lymphoma
• B lineage
  • Mediastinal large B cell lymphoma
    • Sclerosis may obscure the diagnosis
  • Extranodal marginal zone lymphoma
    • Rare
    • May be associated with cyst formation
    • Frequently associated with autoimmune disorders
• T lineage
  • Precursor T lymphoblastic leukemia/lymphoma
    • Phenotype is identical to normal cortex and to thymomas
• Hodgkin lymphoma
  • Nodular sclerosing type is most common
  • Frequently associated with cyst formation

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Classification / Lists

Non-Thymic Neoplasms that May Arise Primarily in the Thymus

• Hematopoietic
  • Primary mediastinal large B cell lymphoma
  • Extranodal marginal zone lymphoma
  • Precursor T lymphoblastic lymphoma/leukemia
• Germ cell tumors
  • Seminoma (Germinoma)
  • Embryonal carcinoma
  • Yolk sac tumor
  • Teratoma
  • Choriocarcinoma
  • With associated somatic type malignancy
    • Embryonal rhabdomyosarcoma
    • Angiosarcoma
    • Others
  • With associated hematologic malignancy
    • Acute myelogenous leukemia
    • Acute megakaryoblastic leukemia
    • Others

Miscellaneous Thymic Lesions and Conditions

• Atrophy
• Cysts
  • Most are non-specific
  • Neoplasms most commonly associated with cysts
    • Thymoma
    • Seminoma
    • Hodgkin lymphoma
    • Extranodal marginal zone lymphoma
    • Basaloid carcinoma
• Castleman disease
• Dysplasia
• Hyperplasia
  • B cell/lymphoid/germinal center
  • Rebound
  • True thymic
• Microscopic thymoma / nodular hyperplasia of thymic epithelium
• (Ectopic hamartomatous thymoma)

Intrinsic Tumors of the Thymus

• Thymoma
  • Type A
  • Type AB
  • Type B1
  • Type B2
  • Type B3
  • Other types
    • Micronodular with lymphoid stroma
    • Metaplastic
    • Sclerosing
• Thymic carcinoma
  • Low grade
    • Well differentiated squamous
    • Basaloid
    • Adenocarcinoma
    • Adenosquamous
    • Low grade mucoepidermoid
  • High grade
    • Lymphoepithelial-like
    • Large cell undifferentiated
    • Clear cell
    • Sarcomatoid
    • Midline carcinoma with t(15;19)
• Thymic neuroendocrine carcinoma
  • Well differentiated (carcinoid)
  • Poorly differentiated
    • Small cell
    • Large cell
• Miscellaneous
  • Thymolipoma
  • Microscopic thymoma / nodular hyperplasia of thymic epithelium

Bibliography

• See specific lymphoma types for additional references
• Shimosato Y, Mukai K, Matsuno Y. Tumors of the Mediastinum, Atlas of Tumor Pathology, AFIP Fourth Series, Fascicle 11, 2010
• den Bakker MA, Oosterhuis JW. Tumours and tumour-like conditions of the thymus other than thymoma; a practical approach. Histopathology. 2009 Jan;54(1):69-89
• Kuroki S, Nasu K, Murakami K, Hayashi T, Sekiguchi R, Nishida H, Miyagawa K, Kuroki Y, Nawano S. Thymic MALT lymphoma: MR imaging findings and their correlation with histopathological findings on four cases. Clin Imaging. 2004 Jul-Aug;28(4):274-7
• Isaacson PG, Chan JK, Tang C, Addis BJ. Low-grade B-cell lymphoma of mucosa-associated lymphoid tissue arising in the thymus. A thymic lymphoma mimicking myoepithelial sialadenitis. Am J Surg Pathol. 1990 Apr;14(4):342-51
• Lorsbach RB, Pinkus GS, Shahsafaei A, Dorfman DM. Primary marginal zone lymphoma of the thymus. Am J Clin Pathol. 2000 Jun;113(6):784-91
• Lamarre L, Jacobson JO, Aisenberg AC, Harris NL. Primary large cell lymphoma  of the mediastinum. A histologic and immunophenotypic study of 29 cases. Am J Surg Pathol. 1989 Sep;13(9):730-9
• Nakagawa A, Nakamura S, Koshikawa T, Nakayama A, Nagasaka T, Motoori T, Kojima M, Hosomura Y, Ueda R, Mori S, et al. Clinicopathologic study of primary mediastinal non-lymphoblastic non-Hodgkin's lymphomas among the Japanese. Acta Pathol Jpn. 1993 Jan-Feb;43(1-2):44-54
• Cazals-Hatem D, Lepage E, Brice P, Ferrant A, d'Agay MF, Baumelou E, Brière J, Blanc M, Gaulard P, Biron P, Schlaifer D, Diebold J, Audouin J. Primary mediastinal large B-cell lymphoma. A clinicopathologic study of 141 cases compared with 916 nonmediastinal large B-cell lymphomas, a GELA ("Groupe d'Etude des Lymphomes de l'Adulte") study. Am J Surg Pathol. 1996 Jul;20(7):877-88
• Davis RE, Dorfman RF, Warnke RA. Primary large-cell lymphoma of the thymus: a diffuse B-cell neoplasm presenting as primary mediastinal lymphoma. Hum Pathol. 1990 Dec;21(12):1262-8