Role of CT/111 In-octreotide SPECT digital fusion imaging in the localization of locoregional recurrence of medullary thyroid carcinoma.

The case of a female patient affected by a sporadic medullary thyroid carcinoma (pT1N1aM0 at the onset) is reported. The patient had been initially treated by total thyroidectomy and lymphadenectomy of the central and lateral portions of the neck. During the following 30 years of follow-up, the patient experienced 3 consecutive loco-regional tumoral relapses. At the moment of each relapse, an increase of serum calcitonin levels has anticipated the subsequent detection of tumor deposits at clinical and radiological examination (ultrasound, CT scan). It is well known that, after multiple operations, the structures of the neck can present anatomical distortion and fibrosis that can interfere with ultrasound and CT scan interpretation. In the present patient, a scintigraphic examination with 111In-octreotide, that is a specific radio-tracer for somatostatin receptors, allowed to correctly visualize a tumoral relapse in the left thyroid bed, located in deep para-tracheal planes: in that site the CT scan only showed an unspecific solid mass. Furthermore, the utilization of a digital image fusion technique for CT scan and 111In-octreotide SPECT, furnished useful information for the purpose of planning an accurate re-intervention, both morphologic information (mass size, precise site of the mass and their relationship with the surrounding anatomical structures) and functional information (biological characterization of the mass that was classified as a neuroendocrine tumoral deposit with high density of somatostatin receptors