A thymoma is a tumor originating from the epithelial cells of the thymus that is considered a rare malignancy. Thymomas are frequently associated with neuromuscular disorders such as myasthenia gravis;[1] thymoma is found in 20% of patients with myasthenia gravis.[2] Once diagnosed, thymomas may be removed surgically. In the rare case of a malignant tumor, chemotherapy may be used.
Thymoma
An encapsulated thymoma (mixed lymphocytic and epithelial type)
A third of all people with a thymoma have symptoms caused by compression of the surrounding organs by an expansive mass. These problems may take the form of superior vena cava syndrome, dysphagia (difficulty swallowing), cough, or chest pain.[1]
One-third to one-half of all persons with thymoma have no symptoms at all, and the mass is identified on a chest X-ray or CT/CAT scan performed for an unrelated problem.[1]
PathologyEdit
Thymoma originates from the epithelial cell population in the thymus, and several microscopic subtypes are now recognized.[1] There are three principal histological types of thymoma, depending on the appearance of the cells by microscopy:
Type A if the epithelial cells have an oval or fusiform shape (less lymphocyte count);
Type B if they have an epithelioid[clarification needed] shape (Type B has three subtypes: B1 (lymphocyte-rich), B2 (cortical) and B3 (epithelial).);[4]
Type AB if the tumor contains a combination of both cell types.
Thymic cortical epithelial cells have abundant cytoplasm, vesicular nucleus with finely divided chromatin and small nucleoli and cytoplasmic filaments contact adjacent cells. Thymic medullary epithelial cells in contrast are spindle shaped with oval dense nucleus and scant cytoplasm thymoma if recapitulates cortical cell features more, is thought to be less benign.
DiagnosisEdit
CT scan of the chest revealing a large necrotic mass in the left anteriormediastinum (indicated by the red line). Histology later established the diagnosis of a thymoma.Another axial slice of a CT scan of the chest showing a small thymoma anterior to the heart (marked with the red line).
When a thymoma is suspected, a CT/CAT scan is generally performed to estimate the size and extent of the tumor, and the lesion is sampled with a CT-guided needle biopsy. Increased vascular enhancement on CT scans can be indicative of malignancy, as can be pleural deposits.[1] Limited[clarification needed] biopsies are associated with a very small risk of pneumomediastinum or mediastinitis and an even-lower risk of damaging the heart or large blood vessels. Sometimes thymoma metastasize for instance to the abdomen.[5]
The diagnosis is made via histologic examination by a pathologist, after obtaining a tissue sample of the mass. Final tumor classification and staging is accomplished pathologically after formal[clarification needed] surgical removal of the thymic tumor.
The Masaoka Staging System is used widely and is based on the anatomic extent of disease at the time of surgery:[6]
I: Completely encapsulated
IIA: Microscopic invasion through the capsule into surrounding fatty tissue
IIB: Macroscopic invasion into capsule
III: Macroscopic invasion into adjacent organs
IVA: Pleural or pericardial implants
IVB: Lymphogenous or hematogenous metastasis to distant (extrathoracic) sites
TreatmentEdit
Surgery is the mainstay of treatment for thymoma. If the tumor is apparently invasive and large, preoperative (neoadjuvant) chemotherapy and/or radiotherapy may be used to decrease the size and improve resectability, before surgery is attempted. When the tumor is an early stage (Masaoka I through IIB), no further therapy is necessary. Removal of the thymus in adults does not appear to induce immune deficiency. In children, however, postoperative immunity may be abnormal and vaccinations for several infectious agents are recommended. Invasive thymomas may require additional treatment with radiotherapy and chemotherapy (cyclophosphamide, doxorubicin and cisplatin).[1][citation needed].[7] Recurrences of thymoma are described in 10-30% of cases up to 10 years after surgical resection, and in the majority of cases also pleural recurrences can be removed. Recently, surgical removal of pleural recurrences can be followed by hyperthermic intrathoracic perfusion chemotherapy or intrathoracic hyperthermic perfused chemotherapy (ITH).
PrognosisEdit
Prognosis is much worse for stage III or IV thymomas as compared with stage I and II tumors. Invasive thymomas uncommonly can also metastasize, generally to pleura, bones, liver or brain in approximately 7% of cases.[1] A study found that slightly over 40% of observed patients with stage III and IV tumors survived for at least 10 years after diagnosis. The median age of these patients at the time of thymoma diagnosis was 57 years. [8]
Patients who have undergone thymectomy for thymoma should be warned of possible severe side effects after yellow fever vaccination. This is probably caused by inadequate T-cell response to live attenuated yellow fever vaccine. Deaths have been reported.[citation needed]
EpidemiologyEdit
Men and women are equally affected by thymomas. The typical age at diagnosis is 30–40, although cases have been described in every age group, including children.[1]
GalleryEdit
An encapsulated cystic thymoma.
A locally invasive circumscribed thymoma (mixed lymphocytic and epithelial, mixed polygonal and spindle).
Histopathological image of thymoma type B1. Anterior mediastinal mass surgically resected. Hematoxylin & eosin stain.
Histopathological image of thymoma type B1. Anterior mediastinal mass surgically resected. Cytokeratin CAM5.2 immunostain.
Histopathological image representing a noninvasive thymoma type B1, surgically resected. Hematoxylin & eosin.
^ abcdefghijThomas CR, Wright CD, Loehrer PJ (July 1999). "Thymoma: state of the art". Journal of Clinical Oncology. 17 (7): 2280–9. doi:10.1200/JCO.1999.17.7.2280. PMID 10561285.
^Mitchell, Richard Sheppard; Kumar, Vinay; Robbins, Stanley L.; Abbas, Abul K.; Fausto, Nelson (2007). Robbins basic pathology. Saunders/Elsevier. ISBN978-1-4160-2973-1.[page needed]
^Bernard C, Frih H, Pasquet F, Kerever S, Jamilloux Y, Tronc F, Guibert B, Isaac S, Devouassoux M, Chalabreysse L, Broussolle C, Petiot P, Girard N, Sève P (January 2016). "Thymoma associated with autoimmune diseases: 85 cases and literature review". Autoimmunity Reviews. 15 (1): 82–92. doi:10.1016/j.autrev.2015.09.005. PMID 26408958.
^Dadmanesh F, Sekihara T, Rosai J (May 2001). "Histologic typing of thymoma according to the new World Health Organization classification". Chest Surgery Clinics of North America. 11 (2): 407–20. PMID 11413764.
^van Geffen WH, Sietsma J, Roelofs PM, Hiltermann TJ (December 2011). "A malignant retroperitoneal mass--a rare presentation of recurrent thymoma". BMJ Case Reports. 2011: bcr0920114737. doi:10.1136/bcr.09.2011.4737. PMC3229325. PMID 22674945.
^Masaoka A, Monden Y, Nakahara K, Tanioka T (December 1981). "Follow-up study of thymomas with special reference to their clinical stages". Cancer. 48 (11): 2485–92. doi:10.1002/1097-0142(19811201)48:11<2485::AID-CNCR2820481123>3.0.CO;2-R. PMID 7296496.
^Wilkins KB, Sheikh E, Green R, Patel M, George S, Takano M, Diener-West M, Welsh J, Howard S, Askin F, Bulkley GB (October 1999). "Clinical and pathologic predictors of survival in patients with thymoma". Annals of Surgery. 230 (4): 562–72, discussion 572–4. doi:10.1097/00000658-199910000-00012. PMC1420905. PMID 10522726.
External linksEdit
August 29, 2023
thymoma, thymoma, tumor, originating, from, epithelial, cells, thymus, that, considered, rare, malignancy, frequently, associated, with, neuromuscular, disorders, such, myasthenia, gravis, thymoma, found, patients, with, myasthenia, gravis, once, diagnosed, th. A thymoma is a tumor originating from the epithelial cells of the thymus that is considered a rare malignancy Thymomas are frequently associated with neuromuscular disorders such as myasthenia gravis 1 thymoma is found in 20 of patients with myasthenia gravis 2 Once diagnosed thymomas may be removed surgically In the rare case of a malignant tumor chemotherapy may be used ThymomaAn encapsulated thymoma mixed lymphocytic and epithelial type SpecialtyOncology cardiothoracic surgeryUsual onsetAdulthoodTreatmentsurgical removal chemotherapy in malignant cases Contents 1 Signs and symptoms 2 Pathology 3 Diagnosis 3 1 Staging 4 Treatment 5 Prognosis 6 Epidemiology 7 Gallery 8 See also 9 References 10 External linksSigns and symptoms EditA third of all people with a thymoma have symptoms caused by compression of the surrounding organs by an expansive mass These problems may take the form of superior vena cava syndrome dysphagia difficulty swallowing cough or chest pain 1 One third of patients have their tumors discovered because they have an associated autoimmune disorder As mentioned earlier the most common of those conditions is myasthenia gravis MG 10 15 of patients with MG have a thymoma and conversely 30 45 of patients with thymomas have MG Additional associated autoimmune conditions include thymoma associated multiorgan autoimmunity pure red cell aplasia and Good syndrome thymoma with combined immunodeficiency and hypogammaglobulinemia Other reported disease associations are with acute pericarditis agranulocytosis alopecia areata ulcerative colitis Cushing s disease hemolytic anemia limbic encephalopathy myocarditis nephrotic syndrome panhypopituitarism pernicious anemia polymyositis rheumatoid arthritis sarcoidosis scleroderma sensorimotor radiculopathy stiff person syndrome systemic lupus erythematosus and thyroiditis 1 3 One third to one half of all persons with thymoma have no symptoms at all and the mass is identified on a chest X ray or CT CAT scan performed for an unrelated problem 1 Pathology EditThymoma originates from the epithelial cell population in the thymus and several microscopic subtypes are now recognized 1 There are three principal histological types of thymoma depending on the appearance of the cells by microscopy Type A if the epithelial cells have an oval or fusiform shape less lymphocyte count Type B if they have an epithelioid clarification needed shape Type B has three subtypes B1 lymphocyte rich B2 cortical and B3 epithelial 4 Type AB if the tumor contains a combination of both cell types Thymic cortical epithelial cells have abundant cytoplasm vesicular nucleus with finely divided chromatin and small nucleoli and cytoplasmic filaments contact adjacent cells Thymic medullary epithelial cells in contrast are spindle shaped with oval dense nucleus and scant cytoplasm thymoma if recapitulates cortical cell features more is thought to be less benign Diagnosis Edit CT scan of the chest revealing a large necrotic mass in the left anterior mediastinum indicated by the red line Histology later established the diagnosis of a thymoma Another axial slice of a CT scan of the chest showing a small thymoma anterior to the heart marked with the red line When a thymoma is suspected a CT CAT scan is generally performed to estimate the size and extent of the tumor and the lesion is sampled with a CT guided needle biopsy Increased vascular enhancement on CT scans can be indicative of malignancy as can be pleural deposits 1 Limited clarification needed biopsies are associated with a very small risk of pneumomediastinum or mediastinitis and an even lower risk of damaging the heart or large blood vessels Sometimes thymoma metastasize for instance to the abdomen 5 The diagnosis is made via histologic examination by a pathologist after obtaining a tissue sample of the mass Final tumor classification and staging is accomplished pathologically after formal clarification needed surgical removal of the thymic tumor Selected laboratory tests can be used to look for associated problems or possible tumor spread These include full blood count protein electrophoresis antibodies to the acetylcholine receptor indicative of myasthenia electrolytes liver enzymes and renal function 1 Staging Edit The Masaoka Staging System is used widely and is based on the anatomic extent of disease at the time of surgery 6 I Completely encapsulated IIA Microscopic invasion through the capsule into surrounding fatty tissue IIB Macroscopic invasion into capsule III Macroscopic invasion into adjacent organs IVA Pleural or pericardial implants IVB Lymphogenous or hematogenous metastasis to distant extrathoracic sitesTreatment EditSurgery is the mainstay of treatment for thymoma If the tumor is apparently invasive and large preoperative neoadjuvant chemotherapy and or radiotherapy may be used to decrease the size and improve resectability before surgery is attempted When the tumor is an early stage Masaoka I through IIB no further therapy is necessary Removal of the thymus in adults does not appear to induce immune deficiency In children however postoperative immunity may be abnormal and vaccinations for several infectious agents are recommended Invasive thymomas may require additional treatment with radiotherapy and chemotherapy cyclophosphamide doxorubicin and cisplatin 1 citation needed 7 Recurrences of thymoma are described in 10 30 of cases up to 10 years after surgical resection and in the majority of cases also pleural recurrences can be removed Recently surgical removal of pleural recurrences can be followed by hyperthermic intrathoracic perfusion chemotherapy or intrathoracic hyperthermic perfused chemotherapy ITH Prognosis EditPrognosis is much worse for stage III or IV thymomas as compared with stage I and II tumors Invasive thymomas uncommonly can also metastasize generally to pleura bones liver or brain in approximately 7 of cases 1 A study found that slightly over 40 of observed patients with stage III and IV tumors survived for at least 10 years after diagnosis The median age of these patients at the time of thymoma diagnosis was 57 years 8 Patients who have undergone thymectomy for thymoma should be warned of possible severe side effects after yellow fever vaccination This is probably caused by inadequate T cell response to live attenuated yellow fever vaccine Deaths have been reported citation needed Epidemiology EditMen and women are equally affected by thymomas The typical age at diagnosis is 30 40 although cases have been described in every age group including children 1 Gallery Edit An encapsulated cystic thymoma A locally invasive circumscribed thymoma mixed lymphocytic and epithelial mixed polygonal and spindle Histopathological image of thymoma type B1 Anterior mediastinal mass surgically resected Hematoxylin amp eosin stain Histopathological image of thymoma type B1 Anterior mediastinal mass surgically resected Cytokeratin CAM5 2 immunostain Histopathological image representing a noninvasive thymoma type B1 surgically resected Hematoxylin amp eosin Thymoma FNA specimen Field stain See also EditMediastinal tumorReferences Edit a b c d e f g h i j Thomas CR Wright CD Loehrer PJ July 1999 Thymoma state of the art Journal of Clinical Oncology 17 7 2280 9 doi 10 1200 JCO 1999 17 7 2280 PMID 10561285 Mitchell Richard Sheppard Kumar Vinay Robbins Stanley L Abbas Abul K Fausto Nelson 2007 Robbins basic pathology Saunders Elsevier ISBN 978 1 4160 2973 1 page needed Bernard C Frih H Pasquet F Kerever S Jamilloux Y Tronc F Guibert B Isaac S Devouassoux M Chalabreysse L Broussolle C Petiot P Girard N Seve P January 2016 Thymoma associated with autoimmune diseases 85 cases and literature review Autoimmunity Reviews 15 1 82 92 doi 10 1016 j autrev 2015 09 005 PMID 26408958 Dadmanesh F Sekihara T Rosai J May 2001 Histologic typing of thymoma according to the new World Health Organization classification Chest Surgery Clinics of North America 11 2 407 20 PMID 11413764 van Geffen WH Sietsma J Roelofs PM Hiltermann TJ December 2011 A malignant retroperitoneal mass a rare presentation of recurrent thymoma BMJ Case Reports 2011 bcr0920114737 doi 10 1136 bcr 09 2011 4737 PMC 3229325 PMID 22674945 Masaoka A Monden Y Nakahara K Tanioka T December 1981 Follow up study of thymomas with special reference to their clinical stages Cancer 48 11 2485 92 doi 10 1002 1097 0142 19811201 48 11 lt 2485 AID CNCR2820481123 gt 3 0 CO 2 R PMID 7296496 NCCN Thymoma Guidelines 2016 NCCN Thymoma Guidelines PDF NCCN Guidelines PDF a href Template Cite web html title Template Cite web cite web a Check archive url value help CS1 maint url status link Wilkins KB Sheikh E Green R Patel M George S Takano M Diener West M Welsh J Howard S Askin F Bulkley GB October 1999 Clinical and pathologic predictors of survival in patients with thymoma Annals of Surgery 230 4 562 72 discussion 572 4 doi 10 1097 00000658 199910000 00012 PMC 1420905 PMID 10522726 External links Edit Retrieved from https en wikipedia org w index php title Thymoma amp oldid 1106155102, wikipedia, wiki, book, books, library,
