July - September 2016, Volume 12, Issue 3

Stefanescu C, Ionescu L, R Danila, Butcovan D, Tibu R, Bilha S, Timofte D, Vulpoi C

99mTc Mibi Thymic Scintigraphy in Diagnosis and Therapeutic Decision Making: What is Behind the Image?

Acta Endo (Buc) 2016, 12 (3): 249-256
doi: 10.4183/aeb.2016.249

Context. Despite CT being generally used in thymic pathology, in the case of regions with the same tissue density, only functional radioisotopic imaging can hint towards malignity. Objectives. To assess the usefulness of 99mTc MIBI scintigraphy for diagnosis and treatment planning in thymoma, in relation with the radiotracer uptake mechanism. Patients and methods. 99mTc MIBI thymic scans for 19 patients diagnosed with thymic disorders were assessed using tumor uptake ratio (UR). Specimens of thymectomies were examined and cytological assessments were correlated with the UR. Results. The UR of all surgical patients was higher than 1.2, with a 1.5 cutoff between lymphoid hyperplasia and thymoma. The UR values were correlated with the histopathologic diagnosis (Pearson correlation 0.91, significant at p<0.01). The highest UR was 3.24, found in the case of an AB thymoma where the rate lymphocytes/ epithelial cells (L/E) was 1.6. In B1 thymoma UR was 1.14 and L/E was 2.46. Conclusion. Phenotype differences between thymoma types correlate with 99mTc MIBI cellular uptake: lower rate L/E corresponds to higher UR, higher malignity potential and invasiveness. A thymic 99mTc MIBI UR higher than 1.5, corresponding to a CT tumoral image, is suggestive for a thymoma, requiring surgical treatment first.

Keywords: Thymoma, Thymic Hyperplasia, 99mTc MIBI scan, Radiotracer Uptake Mechanism

Correspondence: Lidia Ionescu MD, PhD, “Gr.T.Popa” University of Medicine and Pharmacy, Dept. of Surgery, 16th Universitatii Street, Iasi, 700115, Romania, E-mail: lidia.ionescu07@yahoo.com