In this article, we will discuss medullary thyroid carcinoma (MTC) as it relates to children, with a particular focus on diagnosis and genetic screening. We will base our article on 2 brilliant studies by 2 groups of scientists: Kiriakopoulos and colleagues, who wrote about the current state of play with regards to MTC in children and future perspectives, as well as Graves and Gosnell, who carefully documented the presentation of MTC in children.
Pediatric Presentation
MTC is an exceedingly rare cancer that accounts for only about 5% of thyroid cancers in children. It originates from the parafollicular C cells of the thyroid glands. MTC can be sporadic or inherited, but in children, it is overwhelmingly an inherited disease. Graves and Gosnell wrote, “Though MTC may be either sporadic or inherited, in children, over 95% of MTC is hereditary, as part of the multiple endocrine neoplasia (MEN) syndromes MEN 2A and 2B, and the related variant familial MTC.”
MTC, when detected in children, does carry a better prognosis compared to older patients. “MTC in pediatric patients has a less advanced stage at diagnosis and a significantly better prognosis than adults,” Kiriakopoulos et al wrote.
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However, pediatric MTC does come with its own set of challenges. The researchers continued that “issues that may arise in the management of pediatric MTC include appropriate genetic screening and timely surgical treatment with avoidance of postoperative complications.”
Diagnosis of Pediatric MTC
Usually, the clearest sign of MTC in children (and adults) is a thyroid nodule associated with enlarged neck lymph nodes. Kiriakopoulos et al wrote, “Cutaneous lichen amyloidosis usually manifests with pruritus for many years prior to the occurrence of the skin lesions, and the characteristics of lichenoid papules are present in adult life and rarely in childhood.” In addition, marfanoid characteristics, as well as skeletal manifestations, such as bifid ribs and pectus excavatum, may be present.
Read more about MTC diagnosis
One of the most common preoperative procedures undertaken in MTC patients is a neck ultrasound scan. Kiriakopolous et al wrote, “Preoperatively, ultrasound is the most common imaging technique for detecting neck lesions, thyroid nodules, and regional lymph node metastases. Furthermore, fine-needle aspiration with the examination of calcitonin washout fluid may help in the diagnosis of MTC.” Ultrasound is also useful postoperatively to track the success of thyroidectomy performed.
CT scans are ideal for detecting the involvement of cervical or mediastinal lymph nodes as well as lung parenchyma. It is also excellent for imaging liver metastases.
MRI scans are generally better for detecting any involvement of the spinal cord, bone marrow, or soft tissue. For these reasons, MRI can be a useful imaging modality to evaluate the extent of the disease.
Genetic Testing and Counseling
Graves and Gosnell wrote, “All children who are diagnosed with MTC, or who are at risk of inheriting a RET mutation, should undergo genetic counseling and genetic testing.” Kiriakopolous et al agree, writing that “genetic testing for RET mutations is crucial for the diagnosis of MTC.”
We refer to the guidelines set by the American Thyroid Association (ATA) as quoted by Graves and Gosnell: “The ATA recommends genetic counseling and genetic testing be offered to first-degree relatives of patients with hereditary MTC, infants or young children with the classic phenotype of MEN2B (and their parents), patients with cutaneous lichen amyloidosis, and infants or young children with Hirschsprung’s disease and exon 10 RET germline mutations.”
There is a unique dilemma faced by physicians when treating children with MTC, namely whether and when prophylactic thyroidectomy should be performed. It should be emphasized here that prophylactic thyroidectomy is a surgical procedure done before signs of MTC appear in children who are found to have a RET mutation through genetic testing. The ATA defines it as “removal of the thyroid before MTC develops or while it is clinically unapparent and confined to the gland.”
Read more about MTC patient education
Prophylactic surgery has always been controversial, but it is especially tricky when children are involved (since they are unable to give consent in the same way that adults do). Also, children who have had prophylactic thyroidectomy performed will need to be on lifelong thyroid hormone replacement therapy. In addition, there is an increased risk of complications such as hypoparathyroidism.
There are, however, certain factors that may lead physicians toward or away from performing prophylactic thyroidectomy; among them are:
- The specific RET mutation that was detected
- The basal or stimulated calcitonin levels
- The findings of the neck ultrasound scan.
- The earliest age of MTC diagnosis in the patient’s family.
Hence, it is right when deciding whether prophylactic thyroidectomy should be performed in pediatric patients to take a multidisciplinary approach so that as many expert opinions are taken into consideration before such a permanent decision is made.
Preserving Quality of Life
In this article, we have discussed the unique presentation of MTC in children, especially the fact that most of them are hereditary as opposed to sporadic. Imaging modalities help stage the disease, but genetic screening is most helpful in helping physicians decide whether drastic prophylactic intervention is needed.
Ultimately, what’s most important for physicians is determining how the pediatric patient’s quality of life can be maintained with as little interruption as possible. Hopefully, new solutions in the future will make that decision a little less difficult.
References
Kiriakopoulos, A, Dimopoulou A, Nastos C, et al. Medullary thyroid carcinoma in children: current state of the art and future perspectives. J Pediatr Endocrinol Metab. Published online September 30, 2021. doi:10.1515/jpem-2021-0502
Graves CE, Gosnell JE. Medullary thyroid carcinoma in children. Semin Pediatr Surg. 2020;29(3):150921. doi:10.1016/j.sempedsurg.2020.15092
