Precise diagnostic work up of a suspected thymic pathology in patients with
myasthenia gravis (MG) is very important for potential surgical implications and further disease course. In this study the diagnostic value of combined preoperative radiological (CAT scan) and nuclear based imaging (
octreotide and
thallium scintigraphy) in patients with MG was evaluated. Twenty four patients were included. Histopathology revealed
thymoma in nine patients,
thymic carcinoma (TC) in one patient, lymphofollicular
hyperplasia in seven patients, and involuted thymus in another seven patients. Diagnostic sensitivity for detecting
thymoma/TC was 80 % in CAT scan as well as in
somatostatin scintigraphy; the combination of both procedures reached 90 %. However, the diagnostic specifity to exclude
thymoma in CAT scan was 100 % and in
octreotide scintigraphy 85.7 %. Semiquantitative
octreotide uptake significantly correlated with histological grading of
thymoma/TC (r = 0.764) and histological proliferation rate Ki67 (r = 0.894).
Thallium scintigraphy was positive only in one out of four
thymoma cases. In this study,
somatostatin scintigraphy has been shown to be a useful additional diagnostic technique in detecting thymic
malignancies in patients with MG. These results might be especially helpful in patients with late onset MG as these patients are in general no candidates for
thymectomy.