Mediastinal tumors

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Mediastinal tumor
Primitive neuroepithelium intermed mag.jpg
Micrograph of the primitive neuroepithelium of an immature teratoma of the mediastinum. H&E stain.
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A mediastinal tumor is a tumor in the mediastinum, the cavity that separates the lungs from the rest of the chest. It contains the heart, esophagus, trachea, thymus, and aorta.

Contents

The mediastinum has three main parts: the anterior mediastinum (front), the middle mediastinum, and the posterior mediastinum (back). Masses in the anterior portion of the mediastinum can include thymoma, lymphoma, pheochromocytoma, germ cell tumors including teratoma, thyroid tissue, and parathyroid lesions. Masses in this area are more likely to be malignant than those in other compartments. [1] [2]

The most common mediastinal masses are thymoma (20% of mediastinal tumors), usually found in the anterior mediastinum, followed by neurogenic tumor (15–20%) located in the anterior mediastinum. [3] Lung cancer typically spreads to the lymph nodes in the mediastinum.

Masses in the posterior portion of the mediastinum tend to be neurogenic in origin, and in adults tend to be of neural sheath origin including neurilemomas and neurofibromas. [3]

Types

Anterior Mediastinal Masses

50% of mediastinal masses occur in the anterior compartment. The most common anterior masses are commonly known by the '4 T's' which refer to thymomas, teratomas, thyroid tissue and 'terrible' lymphomas. [4]

Thymic carcinoma and thymoma

The thymus is a lymphatic organ in the anterior mediastinum where lymphocytes, immune system cells, are produced and matured. It is most prominent in infants and begins to involute at 1 year of age. Tumors of this organ are the most common primary anterior mediastinal tumor, comprising 20% of all mediastinal cancers. [5] Thymomas and thymic carcinomas most commonly occur between ages 40 and 60 and only rarely occur in children. Patients usually initially present with an incidental finding on imaging, symptoms due to compressive effects or symptoms due to an associated paraneoplastic syndrome such as myasthenia gravis. Half of patients with a thymoma are found to have myasthenia gravis, an autoimmune disorder presenting with diplopia, ptosis, dysphagia, weakness or fatigue. [6]

Both thymic tumors originate from thymic epithelial cells. Under microscope, thymomas have lobulations with bands of fibrous stroma, while thymic carcinomas lack lobulated architecture and have more cystic and necrotic changes. [7] Thymomas can develop into carcinomas, although this only occurs after about a decade. [4] Diagnosis is achieved through CT or MRI of the chest, which can differentiate between other mediastinal masses. Treatment may include chemoradiotherapy, immunotherapy, and/or surgical resection. [7]

Lymphoma

Micrograph of a primary mediastinal large B-cell lymphoma, a rare type of lymphoma that arises in the mediastinum. H&E stain. Primary mediastinal large B-cell lymphoma - very high mag.jpg
Micrograph of a primary mediastinal large B-cell lymphoma, a rare type of lymphoma that arises in the mediastinum. H&E stain.

Lymphomas comprise 15% of primary mediastinal masses and 45% of anterior mediastinal masses in children. The most common are nodular sclerosing Hodgkin lymphoma, primary mediastinal large B-cell lymphoma and lymphoblastic lymphoma. Most are seen in the anterior compartment and rest are seen in middle compartment. Hodgkin's lymphoma usually present in 40–50's with nodular sclerosing type (7), and non-Hodgkin's appears in all age groups. There is also primary mediastinal B-cell lymphoma with exceptionally good prognosis. [8] [9] [10]

Common symptoms of a mediastinal lymphoma of include fever, weight loss, night sweats, and compressaive symptoms such as pain, dyspnea, wheezing, Superior vena cava syndrome, pleural effusions. Diagnosis is usually by CT or MRI showing lobulated mass. Confirmation done by tissue biopsy of accompanying nodes if any, mediastinoscopy, mediastinotomy, or thoracotomy. FNA biopsy is usually not adequate. Treatment of mediastinal Hodgkin's involves chemotherapy and/or radiation. Prognosis is variable and dependent on the lymphoma type and staging. Stage 1 and 2a Hodgkin lymphoma has a good prognosis with 5-year overall survival of 90%.

Germ Cell Tumors

Germ cell tumors comprise 15% of mediastinal masses and usually affect young adult men between the ages of 18 and 29. These are rare tumors that develop from reproductive cells that grow in the chest instead of the gonads during early development. These tumors resemble testicular germ cell tumors and are classified into three types: teratomas, seminomas, and non-seminomatous tumors such as yolk sac tumors or embryonal carcinomas [11] . Teratomas are the most common type to form in the mediastinum.

Tumors are initially asymptomatic but may cause chest pain, cough, or shortness of breath when the size causes compression on surrounding structures. The tumor is diagnosed by CT and MRI scans as well as blood markers like AFP, β-hCG and LDH that help classify the type of germ cell tumor. [11] Most teratomas are benign tumors but require close follow-up and treatment. Teratomas are associated with Klinefelter syndrome.Teratomas are usually noncancerous and treated with surgery, while seminomas and non-seminomatous tumors are more aggressive and treated with chemotherapy and surgery. [12] The outlook depends on the tumor classification, with seminomas and teratomas having excellent prognosis and non-seminomatous tumors having a higher chance of metastasis. [13]

Diagnosis

In several editions of Physical Diagnosis, [14] concerning mediastinal tumors the author writes:

According to Christian1 the mediastinal neoplasms which are neither so rare nor so obscure as to make diagnosis practically impossible are: (1) Sarcoma (including lymphosarcoma, leucaemic growths, and Hodgkins' disease; (2) Teratoma and cyst.

Many signs and symptoms of a mediastinal tumor do not distinguish between these two principal classes of mediastinal tumor. However, on a radiograph usually the former class will have an irregular shape and the latter class will have a smooth spherical or ovoid shape. A large minority of patients with a mediastinal teratoma (including dermoid cyst) will cough up hair. [14] For a differential diagnosis, the key is to exclude aneurysm.[ citation needed ]

See also

References

  1. ↑ Macchiarini P, Ostertag H (February 2004). "Uncommon primary mediastinal tumours". Lancet Oncol. 5 (2): 107–18. doi:10.1016/S1470-2045(04)01385-3. PMID   14761815.
  2. ↑ Davis RD, Oldham HN, Sabiston DC (September 1987). "Primary cysts and neoplasms of the mediastinum: recent changes in clinical presentation, methods of diagnosis, management, and results". Ann. Thorac. Surg. 44 (3): 229–37. doi: 10.1016/S0003-4975(10)62059-0 . PMID   2820323.
  3. 1 2 "Neurogenic Tumors of the Mediastinum" . Retrieved 28 July 2012.
  4. 1 2 Almeida, Patricia T.; Heller, Daniel (2025), "Anterior Mediastinal Mass", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID   31536215 , retrieved 30 October 2025
  5. ↑ Jilani, Talha N.; Killeen, Robert B.; Siddiqui, Abdul H. (2025), "Mediastinal Cancer", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID   30020603 , retrieved 30 October 2025
  6. ↑ Gilhus, Nils E. (29 December 2016). "Myasthenia Gravis". New England Journal of Medicine. 375 (26): 2570–2581. doi:10.1056/NEJMra1602678. ISSN   0028-4793. PMID   28029925.
  7. 1 2 Robinson, Shawn P.; Akhondi, Hossein (2025), "Thymoma", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID   32644717 , retrieved 30 October 2025
  8. ↑ Rosenwald A, Wright G, Leroy K, et al. (September 2003). "Molecular diagnosis of primary mediastinal B cell lymphoma identifies a clinically favorable subgroup of diffuse large B cell lymphoma related to Hodgkin lymphoma". J. Exp. Med. 198 (6): 851–62. doi:10.1084/jem.20031074. PMC   2194208 . PMID   12975453.
  9. ↑ Rodríguez J, Gutiérrez A, Piris M (June 2008). "Primary mediastinal B-cell lymphoma: treatment and therapeutic targets". Leuk. Lymphoma. 49 (6): 1050–61. doi:10.1080/10428190801958994. PMID   18452109. S2CID   24939529.
  10. ↑ Savage KJ (May 2006). "Primary mediastinal large B-cell lymphoma". Oncologist. 11 (5): 488–95. doi: 10.1634/theoncologist.11-5-488 . PMID   16720849.
  11. 1 2 Kang, James; Mashaal, Hyfaa; Anjum, Fatima (2025), "Mediastinal Germ Cell Tumors", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID   33085379 , retrieved 31 October 2025
  12. ↑ Moraru, Liviu; Mitranovici, Melinda-Ildiko; Chiorean, Diana Maria; Coroș, Marius; Moraru, Raluca; Oală, Ioan Emilian; Turdean, Sabin Gligore (23 April 2023). "Immature Teratoma: Diagnosis and Management-A Review of the Literature". Diagnostics (Basel, Switzerland). 13 (9): 1516. doi: 10.3390/diagnostics13091516 . ISSN   2075-4418. PMC   10177811 . PMID   37174909.
  13. ↑ Ozgun, Guliz; Nappi, Lucia (8 February 2023). "Primary Mediastinal Germ Cell Tumors: A Thorough Literature Review". Biomedicines. 11 (2): 487. doi: 10.3390/biomedicines11020487 . ISSN   2227-9059. PMC   9953372 . PMID   36831022.
  14. 1 2 Cabot, Richard C (1919). Physical diagnosis (7th ed.). New York: William Wood and Company. p. 527.

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