CA19-9 (sialyl Lewis[a] antigen) was originally described as a gastrointestinal system and pancreas specific tumour marker. Immunohistochemical studies have demonstrated that CA19-9 is expressed in both differentiated and anaplastic thyroid carcinomas. Increased serum levels of CA 19-9 were reported in few patients with anaplastic thyroid cancer; however, to the best of our knowledge, there is no previous report about serum levels of CA 19-9 in differentiated thyroid cancer. Sixty-eight years old man underwent low anterior resection for the adenocarcinoma of rectum and after the subsequent chemotherapy he was in the remission of the disease. An increase in serum CA 19-9 from 11 to 53 kIU/l (normal values <39; ECLIA Roche) was detected during regular check-up 6 years after initial treatment. The only remarkable pathological finding was the focus of hypermetabolism in the upper mediastinum on PET scan. Ultrasonography of the thyroid and CT confirmed 95 ml nodule in right thyroid lobe. FNAB was performed with the cytological finding of oncocytic tumour. Total thyroidectomy followed. Histological examination confirmed oncocytic variant of minimally invasive follicular cancer together with lymphocytic thyroiditis. Immunohistochemistry revealed the dispersed positivity of CA 19-9. Two months after operation, patient underwent the diagnostic iodine scan with the finding of 2 foci of isotope accumulation in mediastinum suspected for lymph node metastasis. Therapeutic dose 5.5 GBq of 131 I was immediately applied. CA 19-9 levels normalised during 1 month. The patient is now, 14 months after thyroidectomy, in the complete remission of both thyroid cancer (undetectable serum thyroglobulin, negative ultrasound of the neck and negative diagnostic radioiodine scan) and of rectosigmoid cancer.
Conclusion: Serum levels of CA-19-9 could be increased also in differentiated thyroid cancer and could lead to a false suspicion of GIT tumour.
Prague, Czech Republic
24 - 28 Apr 2010
European Society of Endocrinology