Outcome of Treatment for Medullary Thyroid Carcinoma-a Single Centre Experience

We conducted this study to evaluate the demography, clinical presentation, management and outcomes of medullary thyroid carcinoma (MTC) from the Indian context. This was a retrospective study of patients with MTC managed between January 2008 and December 2016. All pertinent data was collected and the results were analysed using STATA (v.13.1). MTC accounted for 90/2022 (4.45%) patients managed with thyroid cancer during the study period. The mean age of presentation was 40 years (range 14-70 years) with 47 males and 43 females. The most common presentation included goitre with cervical lymphadenopathy seen in 60 patients (66.7%). There were 11 patients (12.2%) with systemic metastasis at presentation. Rearranged during transfection (RET) testing was performed in 71 patients and was positive in 25 (35.2%). The mutations among these patients were seen in the following codons: 634 (12), 804 (8), 790 (3) and 618 (2). Persistent hypercalcitoninemia (calcitonin > 50 pg/ml) was observed in 62/80 (77.5%) patients. Forty patients underwent a meta-iodo-benzyl-guanidine (MIBG) scan in the postoperative period, 10 were positive. The mean duration of follow-up was 32 months and 10 patients defaulted from follow-up. Sixteen patients developed metastasis during the period of follow-up while eight patients expired. The mean survival was 85.75 months (95% CI 78.7-92.7). MTC accounted for 4.5% of thyroid carcinomas in this cohort among which 35% were hereditary. Persistent hypercalcitoninemia following surgery is seen in more than 70% of patients but this does not affect survival. RET screening should be performed for all patients with MTC as curative surgery can be offered for mutation positive offspring.

Precursor lesions of endocrine system neoplasms

The concept of precursor lesions of endocrine neoplasms is a new and interesting topic in endocrine pathology. A variety of clinicopathological conditions are associated with a sequence of cellular changes from hyperplasia to neoplasia; dysplasia is, in contrast, quite rare. The majority of precursor lesions is associated with familial genetic syndromes. These include C-cell hyperplasia in thyroid that is associated with familial medullary thyroid carcinoma, adrenal medullary hyperplasia as a precursor of phaeochromocytomas in MEN2 syndrome, rare pituitary adenohypophyseal cell hyperplasia in familial syndromes associated with pituitary adenomas, MEN1-related precursor gastric enterochromaffin-like cell (ECL) hyperplasia, and duodenal gastrin producing (G) and/or somatostatin producing (D) cell hyperplasia that give rise to type II gastric neuroendocrine tumours (NETs) and duodenal NETs, respectively, and MEN1- or VHL-related islet hyperplasia, islet dysplasia and ductulo-insular complexes that are associated with pancreatic NETs. Other hyperplasias are not thought to be associated with genetic predisposition. Some are attributed to inflammation; autoimmune chronic atrophic gastritis-related ECL hyperplasia can progress to type I gastric NETs, and EC (enterochromaffin) cell or L cell hyperplasia associated with inflammatory bowel diseases can progress to colorectal NETs. In the lung, diffuse idiopathic pulmonary neuroendocrine cell hyperplasia can give rise to peripherally-located low grade pulmonary NETs and tumourlets (neuroendocrine microtumours <5  mm). Rarely, secondary hyperplasias develop into autonomous neoplasms, as in tertiary hyperparathyroidism or pituitary thyrotroph adenomas in primary hypothyroidism. While some precursor lesions, such as thyroid C cell hyperplasia, represent frankly premalignant conditions, others may represent a sequence of proliferative changes from hyperplasia to benign neoplasia that may also progress to malignancy.

Hereditary medullary thyroid carcinoma: the management dilemma

Hereditary medullary thyroid carcinoma (hereditary MTC) is a rare malignancy, accounting for 25-30% of all MTC. It occurs as part of multiple endocrine neoplasia type 2 (MEN 2). Autosomal dominant gain-of-function mutations in the RET proto-oncogene is the cause of the disease, in which the common mutations are codons 609, 611, 618, 620, 630, 634 and 918. In recent years, the spectrum of RET gene mutations has changed. The classical mutations reduced, whereas the less aggressive mutations increased. Hereditary MTC is a time-dependent disease. Stages of the disorder at diagnosis can significantly influence survival rates. Based on the genotype-phenotype, RET mutations have been classified into four risk levels by American Thyroid Association (ATA) at 2009. The classification system guides the hereditary MTC management, including risk assessment, biochemical screenings and surgical intervention. Though the application of genetic testing and codon-specific phenotypes in hereditary MTC diagnosis is effective with high accuracy, there are some difficulties in implementing RET gene testing as a routine for MTC diagnosis. And most of carriers with RET mutations did not undergo thyroidectomy at the age recommended by the ATA guidelines. The aim of the study is to review the hereditary MTC and discuss the management dilemma.