title: Metastatic medullary thyroid cancer presenting with elevated levels of CA 19-9 and CA 125.
abstract: BACKGROUND
  Calcitonin and carcinoembryonic antigen (CEA) are established markers of medullary thyroid cancer (MTC), used in the diagnosis and monitoring of disease and its progression. In clinical practice, various other tumor markers are utilized in the follow-up of different malignancies, although their utility has not been well described in MTC. CA 19-9 antigen, routinely used in the monitoring of pancreatic cancer, also has been detected in the tissue of approximately 6% of MTCs. However, its presence has never been reported in the serum of these patients. Elevation of CA 125 antigen, utilized as a tumor marker for ovarian cancer, has never been reported in MTC. We report a novel finding of metastatic MTC presenting with elevated CA 19-9 and CA 125 serum levels, with concurrent tissue staining for these antigens.
  
  
  CONCLUSIONS
  A 56-year-old woman with multiple endocrine neoplasia 2B syndrome, post subtotal thyroidectomy for MTC in childhood, presented with extensive metastatic spread of MTC to the lungs and liver, 47 years after the original diagnosis. The patient's calcitonin level decreased from 2950 to 261 pg/mL (reference range: <20 pg/mL) over a 20-year period. The serum CEA level was elevated at 6800 ng/mL (reference range: <5.1 ng/mL). Because of a concern for an alternate malignancy, serum CA 19-9 and CA 125 tumor markers were measured and found to be significantly elevated, at 39,334 U/mL (reference range: <35.1 U/mL) and 96.2 U/mL (reference range: 7-41 U/mL), respectively. Immunostaining of the metastatic MTC tissue showed patchy staining for calcitonin, strongly positive staining for CEA and CA 19-9, and weakly positive staining for CA 125.
  
  
  CONCLUSIONS
  Drawing from experience with CA 19-9 and CA 125 tumor markers in other malignancies, we propose that they may be associated with aggressive forms of MTC with significant metastatic potential.
authors.affiliation: Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York 10467, USA. sofiyamilman@gmail.com
authors.forename: Sofiya
authors.initials: S
authors.lastname: Milman
authors.forename: Kathleen D
authors.initials: KD
authors.lastname: Whitney
authors.forename: Norman
authors.initials: N
authors.lastname: Fleischer
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism; D018394:CA-125 Antigen / Q000096:biosynthesis*; D018395:CA-19-9 Antigen / Q000096:biosynthesis*; D018278:Carcinoma, Neuroendocrine; D003062:Codon; D005260:Female; D006801:Humans; D008875:Middle Aged; D018814:Multiple Endocrine Neoplasia Type 2b / Q000097:blood / Q000150:complications; D009154:Mutation; D009362:Neoplasm Metastasis; D013964:Thyroid Neoplasms / Q000097:blood / Q000150:complications / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor; D018394:CA-125 Antigen; D018395:CA-19-9 Antigen; D003062:Codon