Considerations regarding the role of 99m Tc-tetrofosmin thymic scintigraphy in thymomas

1. Considerations regarding the role of 99mTc-tetrofosminthymicscintigraphyin thymomas Lidia Ionescu, Cipriana Stefanescu, Carmen Vulpoi, C. Diaconu, Cr. Dragomir

2. CT –mainstay of thymic investigation • Thoracic CT scan has a reliable sensitivity and specificity in detecting thymic lesions • Elective method of diagnosis • One major difficulty is to differentiate for certain between thymic lymphoid hyperplasia and thymoma. • But in equivocal cases, other investigations can add suplimentary informations.

3. MV, male, 46 years old, 6w. history of MG- Oss. III, CT suspicious for thymoma,Op. 2004, pathology- thymic lymphoid hyperplasia + mediastinal ectopies, post. op.- complete remission

4. GE, 19 years old man Hashimoto’s thyroiditis - apr. 2005- L-thyroxine, Hemolytic anemia – oct .2005 (Hb-3,8g/dl, LDH-1444 u/l)-Treatment- steroizi, transfuzii repetate.CT- thymoma, op.dec 2005 Pathology- thymic lymphoid hypertrophy, Result- complete remission of hemolytic anemia

5. PF, female, 21 years old, MG- OSS III, CT- thymic hyperplasia, op. 1997Pathology - lymphocitic thymoma Result - farmacologic remission

6. Imaging investigations • Equivocal cases - thymic scintigraphy can add supplimentary informations to CT aspects. • Equivocal cases: • Association of thyro-thymic lesions • Tumor recurrence • Type of thymic lesions • Ectopic thymomas

7. Scintigraphy with 99mTc-tetrofosmin • Frequently used in the assessment of myocardial perfusion, conducted to incidental extracardiac uptake and detection of a mediastinal mass as it showed in few reported cases in the literature (Kotsalou I, Hawkins M) • This investigation is not yet included in the algorithm of diagnosis for mediastinal mass • But it must be considered a valuable alternative when conventional investigations fail to confirm a clinical suspicion, resulting in adequate decision making.

8. Thymic scintigraphy • Pathological uptake of 99mTc tetrofosmin appears in benign and malignant tumors through an incomplete understood mechanism. • But the increased number of mitochodrias and the degree of perfusion of the lesion seem to play an important role.

9. Thymic scintigraphy • Thymic scintigraphy can asses after the degree of up-take of the radiotracer on the early and late images • Normal thymus, • Hyperplasia • Thymoma • Tumor recurrence • Ectopic thymomas

10. The 99m-Tc Tetrofosmin scintigraphy • Performed with standard doses, according to the worldwide accepted protocol. • An informed consent for the investigation is obtained from all the patients. • An AXIS Gamma camera (Philips), Siemens double-head detection and SPECT was used and acquired data were analyzed with an IBM specialized software.

11. 99m TcTetrofosmin • Lipophile molecule that crosses the cellular membranes according to electrochemical gradient and fluidity of the membrane. • It accumulates mainly in the mitochondria, which explains the fixation in cells with intense metabolism.

12. Equivocal cases • The association hyperthyroidy-myasthenia gravis is present mainly in autoimmune thyropathies such as Hashimoto’s thyroiditis or Grave’s disease • Usually myasthenia gravis is secondary to hyperthyroidy due to thymus hyperplasia and an adequate antithyroid drug treatment or surgery result in remission of thymic hyperplasia.

13. Associated lesionsGrave’s disease-myasthenia gravis • Murakami, Yasuhiro Hosoi demonstrated the presence of thymic hyperplasia in Grave’s disease patients, calculating on CT scan images the size and density of the thymus on untreated and treated Grave’s disease patients. • The conclusion was that thymic hyperplasia regresses in treated patients either with antithyroid drugs or total thyroidectomy

14. Thyro-thymic lesions • Yamanaka K, Nakayama H. reported a case of Grave's disease associated with a mediastinl mass in whom CT scan RMI were suggestive for a thymoma. • The patient underwent total thyroidectomy and thymectomy at the same stage. • Pathology report showed a thymic hyperplasia.

15. AM, 46-year-old woman, 2007 multinodular goitre and myasthenia gravis Thyroid profile (TSH-0.1 µUI/ml, fT4-1.2ng/dl), Thyroid total volume of 65.9 ml. (Prof. dr. C. Vulpoi) Compressive goiter Retrosternalgoiter

16. Total thyroidectomy for MNG-2007,Myasthenia gravis aggravated Normal Chest Normal thymus

17. Thymic scintigraphyHypercaptation of 99mTc-tf. consistent with a thymoma

18. Repeat CT scanAntero- inferior mediastinal massThymectomy, 6 months following TT, june 2008 Paramedian low retrosternal mass Well-encapsulated mass

19. Hyperthyroidism+ectopic thymoma • The thyroid lesion more obvious, was first treated and myasthenia gravis considered wrongly to be secondary and remitting after total thyroidectomy. • On thymic scintigraphy was evident the high uptake of Tc-TF in lower anterior mediastinum with a high suspicion of thymoma. • Pathology report of the specimen was mixt thymoma with capsular microscopic invasion-Masaoka II stage.

20. Equivocal case • Tumour recurrence or postoperative mediastinal scar in patients with recurrent myasthenia gravis??

21. CT, 64 years old, thymoma+MG, Oss.IV, op. 2002, Lymphocitic thymoma (type I malignant thymoma)-Masaoka II ( well encapsulated but microscopic capsular invasion), adhesions to left M. pleura which was resected

22. Radiotherapy 44 Gy, chemotherapy, 1 year CP+PDNPericarditis at 1 year postRxTRemission of MG 5 years, 2008- AChE

25. CT aspects-2009Retrosternal postoperative scar tissue, pericarditis

26. 2009Inflammatory pericarditis

27. 2009- POSTOPERATIVE THYMIC SCINTIGRAPHYLACK OF RADIOTRACER UPTAKE IN THE ANTERIOR MEDIASTINUM

28. Conclusion • The thymic 99mTc tetrofosmin scintigraphy can be efficient in diagnosing and therapeutic decision making when conventional imaging investigations fail to confirm a clinical suspicion.