Normal preoperative calcitonin levels do not always exclude medullary thyroid carcinoma in patients with large palpable thyroid masses

Diagnosis and management of medullary thyroid carcinoma

Successful treatment of MTC depends heavily on early diagnosis and treatment. Often, this is not possible for sporadic MTC; however, genetic testing for hereditary MTC makes this possible if genetic carriers have surgery before C cells undergo malignant transformation. All patients who have MTC should be tested for RET mutations, including putative sporadic cases. The leukocytes of suspected carriers and sporadic MTC cases should be tested for MEN2-associated germ-line mutations by polymerase chain reaction amplification of the appropriate RET gene exons, including 10, 11,13, 14, 15, and 16 (see Table I). When a RET mutation is found, all first-degree relatives must be screened to determine which individuals carry the gene. If these exons are negative, the other 15 should be sequenced because a small risk of hereditary MTC remains if no germ-line mutation is found. The probability that a first-degree relative will inherit an autosomal dominant gene for MTC from an individual who has sporadic MTC in whom no germ-line mutation is found is 0.18% . Patients who have MEN2B or RET codon 883 or 918 mutation should have a total thyroidectomy within the first 6 months of life, preferably within the first month of life. Patients who have 634 mutations, which account for approximately 70% of all MTC mutations, should undergo thyroidectomy by age 5 years. The recommendations for the timing of prophylactic thyroidectomy are not consistent for the less common mutations (see Table 2). There is a balance between performing prophylactic thyroidectomy earlier than at the youngest age at with MTC has been reported to occur for a specific RET mutation (see Fig. 3 and Table 2) and the complications of thyroidectomy, including permanent hypoparathyroidism and laryngeal nerve damage. Preoperative measurement of plasma free metanephrine and neck ultrasonography always should be done if the diagnosis of MTC is known preoperatively. Initial treatment of MTC is total thyroidectomy, regardless of its genetic type or putative sporadic nature, because surgery offers the only chance for a cure. Treatment with 1311 has no place in the management of MTC. Plasma CT measurements provide an accurate estimate of tumor burden and are especially useful in identifying patients who have residual tumor. Pentagastrin- or calcium-stimulated plasma CT testing is useful in identifying CCH or early MTC in carriers of RET mutations that are associated with late onset MTC. Pheochromocytoma may occur before or after MTC and is an important cause of mortality, even in young patients. HPT is an important aspect of MEN2A and requires surgery according to current guidelines for the management of primary HPT. Early thyroidectomy and appropriate management of pheochromocytoma clearly have modified the course of this disease, but more research is necessary in kindreds who have rare MTC mutations. Moreover, new treatments for widespread MTC are necessary because current chemotherapy agents offer little benefit. New drugs that lock the action of tyrosine kinase offer some hope.

Lack of elevated serum carcinoembryonic antigen and calcitonin in medullary thyroid carcinoma

OBJECTIVE

Medullary thyroid carcinoma (MTC) originates from C-cells. A wide variety of tumor markers including calcitonin (CT), carcinoembryonic antigen (CEA), and chromogranin A are produced by MTC. Surgery remains the only potentially curative therapy, and early detection of the primary remains the most important prognostic factor for a positive outcome for the patient. The following case concerns a 50-year-old woman with histologically proven MTC, who completely lacked serum elevation of both CT and CEA.

METHODS

We performed a total thyroidectomy with lymphadenectomy in the central compartment. Histologic sections were stained for CT, CEA, and chromogranin A. Additionally we examined the patient's blood for mutations in the RET proto-oncogene.

RESULTS

Serum CT and CEA were below the detection level in the serum. The tumor showed weak staining for CT, but strong staining for CEA and chromogranin A. Sequencing of the RET-proto-oncogene revealed no mutations. Five years after the operation, the patient remains well and shows no signs of tumor recurrence.

CONCLUSIONS

We hereby report of a patient with neither plasma elevation of CT nor CEA. From the clinical standpoint, it is important to determine how this subgroup of MTC should be followed because CT and CEA are of no clinical use.

Potential Absence of Prognostic Implications of Severe Preoperative Hypercalcitoninemia in Medullary Thyroid Carcinoma

OBJECTIVE

To evaluate preoperative hypercalcitonine-mia further as a marker of prognosis in patients with medullary thyroid carcinoma (MTC).

METHODS

We reviewed the clinical and laboratory data in six patients (four men and two women, 39 to 76 years old)--three with sporadic MTC, one with familial MTC, and two with multiple endocrine neoplasia type 2A--who had preoperative basal serum calcitonin levels of 400 to 16,000 pg/mL (normal, 0 to 19). Pentagastrin stimulation was performed in patients who had preoperative basal calcitonin levels less than 1,000 pg/mL, and responses ranged from 2,600 to 8,500 pg/mL. Thyroidectomy revealed intrathyroidal MTC in four patients; MTC and nodal metastatic lesions were present in two. The tumor cells were immunoreactive with anti-calcitonin immunoperoxidase staining.

RESULTS

Serum calcitonin and carcinoembryonic antigen levels were normal postoperatively. In serial postoperative evaluation during a follow-up period of 2 to 9 years, stimulated peak plasma calcitonin levels after pentagastrin or calcium infusion were normal (in five patients) or near normal (in one patient), without clinical evidence of recurrent disease. The two patients with nodal metastatic disease have had normal calcitonin levels during a mean duration of follow-up of approximately 3 years.

CONCLUSION

Pronounced preoperative hypercalci-toninemia does not necessarily preclude a favorable short-term outcome in patients with MTC.

Thyroid carcinoma

Thyroid carcinomas are fairly uncommon and include disease types that range from indolent localised papillary carcinomas to the fulminant and lethal anaplastic disease. Several attempts to formulate a consensus about treatment of thyroid carcinoma have resulted in published guidelines for diagnosis and initial disease management. Multimodality treatments are widely recommended, although there is little evidence from prospective trials to support this approach. Surgical resection to achieve local disease control remains the cornerstone of primary treatment for most thyroid cancers, and is often followed by adjuvant radioiodine treatment for papillary and follicular types of disease. Thyroid hormone replacement therapy is used not only to rectify postsurgical hypothyroidism, but also because there is evidence to suggest that high doses that suppress thyroid stimulating hormone prevent disease recurrence in patients with papillary or follicular carcinomas. Treatment for progressive metastatic disease is often of limited benefit, and there is a pressing need for novel approaches in treatment of patients at high risk of disease-related death. In families with inherited thyroid cancer syndromes, early diagnosis and intervention based on genetic testing might prevent poor disease outcomes. Care should be carefully coordinated by members of an experienced multidisciplinary team, and patients should be provided with education about diagnosis, prognosis, and treatment options to allow them to make informed contributions to decisions about their care.

Medullary thyroid cancer

Medullary thyroid cancer is a rare neoplasm that arises from the parafollicular C cells. It occurs in a sporadic form, or less commonly as a hereditary form, as part of multiple endocrine neoplasia syndromes types 2A and 2B. The RET proto-oncogene is currently the primary factor that is implicated in the hereditary forms of this neoplasm. The knowledge about the genetic makeup of the neoplasm impacts upon management as it allows for screening, early detection, and prophylactic treatment. Surgery is the main modality that offers a cure. This entails a total thyroidectomy and vigilant management and surveillance of the neck. Prognosis of patients with MTC is variable, but the more constant factors that affect it are the stage of disease and the age of the patient. The emerging molecular genetic understanding of this malignancy will provide the foundation for prognostic and therapeutic decision-making in the future. Interdisciplinary management by surgeons, endocrinologists, pathologists, radiotherapists, radiologists, and medical oncologists should be sought.