Thyroid Follicular Carcinoma
Female patient 67 year old with a history of follicular thyroid carcinoma treated with radioiodine and surgery a year ago. She was operated on due to recurrency 6 months ago, performing bilateral neck dissection. Currently, presents elevated thyroglobulin levels with negative whole body scan with 131I. Correlative studies: Biopsy: follicular carcinoma with solid pattern with adjacent tissue and extensive venous invasion and lymph node metastases. Thyroglobulin: 1260 ng / mL (N <1).
A PET F18FDG scan was requested and done with a 12 mCi dose , injected with glucose of 84 mg / dL. PET F18FDG volumetric image, showed two intense foci of increased FDG uptake in the right lung, one in the middle third towards the anterior portion and the other posterior in the basal region. In the left lung, there is a large focus on posterobasal region more medial and a small one on its upper part. Also, there is a marked focus of increased activity in anterolateral upper left rib cage and one on the periphery of the left hepatic lobe with protrusion into adjacent diaphragm, posteriorly.
Furthermore, thyroid bed, displays a somewhat elongate and irregular mass of intense accumulation of the tracer, with a focus adjacent lower left of midline, of lesser intensity. Likewise, there is focus on acromioclavicular joints, greater at left, and in hip-degenerative inflammatory aspect. In the rest of the study, usual distribution is observed in brain, spleen, colon, kidney, pyelocalicial systemsand bladder . In conclusion, neck hypermetabolic tissue, bilaterally in the lungs, left ribcage and left hepatic suggestive of malignant tumor activity.
Papillary and follicular thyroid carcinoma may have different characteristics on PET/CT imaging and so should be investigated individually. Combined sensitivity of PET and PET/CT for papillary thyroid carcinoma was 77% by the fixed effect model and 82% by the random-effects model, specificity was calculated as 85% and 84%, respectively. PET and PET/CT are useful modalities in surveillance of papillary thyroid carcinoma (1).
Prestwich RJ et al studied differentiated thyroid carcinoma and concluded that rTSH PET-CT is a useful imaging technique for detecting disease recurrence in patients with iodine-resistant differentiated thyroid cancer (papillary or follicular). Low stimulated thyroglobulin levels are potentially useful in identifying patients unlikely to benefit from a PET-CT scan. PET-CT directly influenced patient management in 17/58 (29%) scans. No positive scans with a stimulated thyroglobulin <8 µg l(-1) was detected (2).
References:
1 Miller ME, Chen Q, Elashoff D, Abemayor E, St John M. Positron emission tomography and positron emission tomography-CT evaluation for recurrent papillary thyroid carcinoma: meta-analysis and literature review.Head Neck. 2011 Apr;33(4):562-5.
2 Prestwich RJ, Viner S, Gerrard G,
Patel CN, Scarsbrook AF. Increasing the yield of recombinant thyroid-stimulating
hormone-stimulated 2-(18-fluoride)-flu-2-deoxy-D-glucose positron emission
tomography-CT in patients with differentiated thyroid carcinoma. Br J Radiol.
2012 Oct;85(1018):e805-13.