Affected patients are typically in the fourth or fifth decades of life. There is a recognized male predominance with M:F ratios around 3:1 2,7.
The majority of patients present with symptoms related to mass effect or invasion of mediastinal and other thoracic structures 7. Carcinoid syndrome is uncommon 1,4.
Up to 50% of affected patients have hormonal abnormalities 2. Approximately 40% of patients have Cushing syndrome as a result of adrenocorticotropic hormone secretion by the tumor; these patients tend to have smaller lesions at the time of diagnosis since they present early with signs of corticosteroid excess. Up to 30% of patients with have advanced-stage disease at presentation 6.
Neuroendocrine tumors of the thymus are rare and believed to arise from thymic cells of neural crest origin (Kulchitsky cells).
Thymic carcinoid tumors are similar to lesions arising within the bronchi, ranges in differentiation and behavior from typical carcinoid to atypical carcinoid to small cell carcinoma 1,3.
Approximately 50% of thymic carcinoids are functionally active 6-7.
They generally tend to be large masses at the presentation that range in size from 6-20 cm.
- non-functioning thymic carcinoids may be seen in association with multiple endocrine neoplasia syndrome type 1 2,6
Radiologically, these tumors typically manifest as large masses with a propensity for local invasion. Focal areas of necrosis and punctate calcification may be present 2,5.
On CT or MRI the masses are usually of heterogeneous attenuation or signal intensity, respectively.
The FDG uptake of carcinoid tumors on CT-PET is variable, with a tendency for the uptake to be low.
On cross-sectional imaging, thymic carcinoids may be indistinguishable from a thymomas 6. However, increased uptake has been reported to correlate with aggressive behaviors such as local invasion and distant metastases 2.
In-111–diethylenetriaminepentaacetic acid (DTPA)-D-Phe1]-octreotide
- accumulates in thymic carcinoids but is not specific as it also accumulated in thymomas and metastatic thymic tumors 7
Treatment and prognosis
They are generally thought to carry a poor prognosis due to high rates of recurrence and metastases. Follow up after resection (if resectable) if often recommended 10.
History and etymology
They are thought to have been initially described by Rosai and Higa in 1972 as a distinct entity from thymomas 11.
- 1. Brant WE, Helms CA. Fundamentals of diagnostic radiology. Lippincott Williams & Wilkins. (2007) ISBN:0781765188. Read it at Google Books - Find it at Amazon
- 2. Haaga JR, Boll D. CT and MRI of the whole body. Mosby. (2009) ISBN:0323053750. Read it at Google Books - Find it at Amazon
- 3. Rubin R. Rubin's Pathology, clinicopathologic foundations of medicine. Philadelphia : Wolters Kluwer/Lippincott Williams & Wilkins, c2008. (2008) ISBN:0781795168. Read it at Google Books - Find it at Amazon
- 4. Nishino M, Ashiku SK, Kocher ON et-al. The thymus: a comprehensive review. Radiographics. 26 (2): 335-48. doi:10.1148/rg.262045213 [pubmed citation]
- 5. Brown LR, Aughenbaugh GL. Masses of the anterior mediastinum: CT and MR imaging. AJR Am J Roentgenol. 1991; 157(6): 1171-80. AJR Am J Roentgenol [pubmed citation]
- 6. Scarsbrook AF, Ganeshan A, Statham J et-al. Anatomic and functional imaging of metastatic carcinoid tumors. Radiographics. 2007;27 (2): 455-77. Radiographics (full text) - doi:10.1148/rg.272065058 - Pubmed citation
- 7. Rosado De Christenson ML, Abbott GF, Kirejczyk WM et-al. Thoracic carcinoids: radiologic-pathologic correlation. Radiographics. 1999;19 (3): 707-36. Radiographics (full text) - Pubmed citation
- 8. Wang DY, Chang DB, Kuo SH et-al. Carcinoid tumours of the thymus. Thorax. 1994;49 (4): 357-60. Free text at pubmed - Pubmed citation
- 9. Fukai I, Masaoka A, Fujii Y et-al. Thymic neuroendocrine tumor (thymic carcinoid): a clinicopathologic study in 15 patients. Ann. Thorac. Surg. 1999;67 (1): 208-11. Pubmed citation
- 10. Sugiura H, Morikawa T, Itoh K et-al. Thymic neuroendocrine carcinoma: a clinicopathologic study in four patients. Ann Thorac Cardiovasc Surg. 2001;6 (5): 304-8. Pubmed citation
- 11. Economopoulos GC, Lewis JW, Lee MW et-al. Carcinoid tumors of the thymus. Ann. Thorac. Surg. 1990;50 (1): 58-61. Pubmed citation
- 12. Luh SP, Kuo C, Liu WS et-al. Carcinoid tumor of the thymus: a clinicopathologic report of two cases with a review of the literature. Int Surg. 2006;90 (5): 270-4. Pubmed citation
- 13. Moran CA, Suster S. Neuroendocrine carcinomas (carcinoid tumor) of the thymus. A clinicopathologic analysis of 80 cases. Am. J. Clin. Pathol. 2000;114 (1): 100-10. doi:10.1309/3PDN-PMT5-EQTM-H0CD - Pubmed citation