Japanese Journal of Clinical Oncology 31:157-161 (2001)
© 2001 Foundation for Promotion of Cancer Research
A Family of Multiple Endocrine Neoplasia Type 2A with the RET Proto-oncogene Mutation in Codon 618 (Cys
Arg)
1First Department of Surgery, Okayama University School of Medicine, Okayama and 2Growth Factor Division, National Cancer Center Research Institute, Tokyo, Japan
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONCASE REPORTDISCUSSIONAcknowledgmentsREFERENCES |
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Multiple endocrine neoplasia type 2 (MEN-2) is a hereditary syndrome characterized by medullary thyroid carcinoma (MTC), pheochromocytoma and hyperplasia or adenoma of the parathyroid gland with hyperparathyroidism. Recent genetic studies have identified the presence of germline missense mutations in the RET proto-oncogene in almost 100% of MEN-2 patients. We report here three generations of one MEN-2 family with rare missense mutation at codon 618 (Cys
Arg) of the RET proto-oncogene. The first patient was surgically treated at the age of 63 years but died of bone metastasis. His two children (29-year-old daughter and 25-year-old son) were treated surgically for MTC and neck lymph node metastasis. Germline mutations of the RET proto-oncogene of these three MTC patients and two children of the 29-year-old daughter (9-year-old female and 7-year-old male) were examined. Three MTC patients and the 9-year-old female possessed the mutation. The phenotype of the family with this rare point mutation of the RET proto-oncogene is reported. |
INTRODUCTION |
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TOPABSTRACTINTRODUCTIONCASE REPORTDISCUSSIONAcknowledgmentsREFERENCES |
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Multiple endocrine neoplasia type-2 (MEN-2) is a hereditary syndrome characterized by medullary thyroid carcinoma (MTC), pheochromocytoma and hyperplasia or adenoma of the parathyroid gland with hyperparathyroidism (1). MEN-2 is usually subdivided into three types: MEN-2A, familial medullary thyroid carcinoma (FMTC) and MEN-2B. All entities are transmitted with variable clinical manifestations. Following the recent discovery of germline missense mutations in the RET proto-oncogene in patients with MEN-2 syndrome (2), direct DNA mutation analysis is now available for identification of individual gene carriers. Such analysis could be conducted before the development and growth of tumors to facilitate subsequent management of members of MEN-2A families and improvement of prognosis (3,4). MTC is found in almost all carriers of mutated RET gene and is usually the first tumor to appear in such individuals (5). The tumor is often aggressive and tends to be associated with extremely poor prognosis and causes death in patients with MEN-2.
We describe three generations of a Japanese family affected by MEN-2A; all family members were examined for RET gene mutation. Three patients and one family member possessed the point mutation at codon 618 (CysArg) of RET gene. Although the codon 618 is the hot spot of RET gene mutation, conversion from Cys to Arg at codon 618 was reported only in three MEN-2A families within our investigation (6,7). Besides presenting this rare case, another purpose of this report is to describe the kindred with MEN-2A, to highlight the significance of DNA analysis of RET mutations in such individuals and to discuss the importance of prophylactic thyroidectomy in carriers of MEN-2A gene. Moreover, analysis of DNA might clarify the genotype–phenotype correlation, which may enhance the clinical management and identify clinical manifestations according to the genotype, thus allowing the development of the best possible treatment strategies for MEN-2A gene carriers.
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CASE REPORT |
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TOPABSTRACTINTRODUCTIONCASE REPORTDISCUSSIONAcknowledgmentsREFERENCES |
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Patients
Proband (Fig. 1; II-1)
A 63-year-old man visited our hospital in November 1995 with a neck tumor. The medical history included hemithyroidectomy at the age of 39 years for thyroid cancer (histology unknown). His mother had died of neck disease at 40 years of age (details unknown). Based on the results of radiological and serological studies, neck and mediastinal lymph node dissection was performed. Pathological examination revealed lymph node metastasis of the thyroid medullary carcinoma. Total thyroidectomy and radical neck dissection was performed soon after pathological diagnosis and germline mutation of the RET proto-oncogene was examined. In spite of surgical treatment, the proband died of multiple bone metastasis at 67 years of age in February 1999. Because MEN-2A was suspected, all family members were screened (Fig. 1).
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Patient 2 (Fig. 1; III-2)
A 29-year-old Japanese female, the daughter of the proband, was asymptomatic and had a negative medical history. Laboratory data showed elevated levels of serum calcitonin (540 pg/ml; normal range, 8.3–69.9) and serum carcinoembryonic antigen (CEA, 5.53 ng/ml; normal range, <5.0). High levels of urinary adrenaline (29 µg/l; normal range, 3–23), noradrenaline (143 µg/l; normal range, 25–131) and dopamine (1520 µg/l; normal range, 150–1000 ) were detected. Serum samples at left renal vein (0.43 ng/l; normal range, 0.05–0.4) vena cava of suprarenal vein (1.3 ng/l; normal range, 0.05–0.4) were elevated. Ultrasonography and computed tomography (CT) revealed a low-density mass measuring 2.5 x 3.0 cm in the left lobe of the thyroid gland (Fig. 2), which was diagnosed as MTC by cytological examination of needle aspirated samples. CT also demonstrated a round, low-density mass in the left adrenal gland measuring 1.2 x 1.0 cm (Fig. 3). A [123I]MIBG (m-iodobenzylguanidine) scintigram showed a high uptake at the position of the left adrenal gland. The case was diagnosed as MTC and pheochromocytoma and total thyroidectomy with neck lymph node dissection and left adrenalectomy were performed. Pathological findings of the resected specimens showed nests of small polygonal cells in the thyroid tumor, which was diagnosed as medullary carcinoma. The adrenal tumor was located in the medullary substance and was positively stained with chromogranin A, confirming the diagnosis of pheochromocytoma. Mutation of the RET proto-oncogene was examined after surgery. Her two children were also screened for the mutation because she possessed the germline mutation. The postoperative course was uneventful and no recurrence was noted during a follow-up period of 14 months.
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Patient 3 (Fig. 1; III-3)
A 25-year-old male, the son of the proband, was asymptomatic and had no significant past medical history. Laboratory data showed elevated levels of serum calcitonin (540 pg/ml; normal range, 8.3–69.9) and serum CEA (5.53 ng/ml; normal range, < 5.0). Ultrasonography and CT revealed a low-density mass measuring 1.0 x 0.8 cm in the left thyroidal lobe, which was subsequently diagnosed as MTC by cytological examination of needle aspirated samples. Further investigations showed no adrenal tumor by CT scan and normal catecholamine levels in both serum and urine. Total thyroidectomy with neck lymph node dissection was performed based on the diagnosis of MTC. Pathological findings of the resected specimens showed medullary carcinoma. Mutation of the RET proto-oncogene was examined after surgery. The postoperative course was uneventful and no recurrence was noted during a 14-month follow-up period.
Family member 4 (Fig. 1; IV-1)
A 9-year-old female, the granddaughter of the proband, was examined for MTC because of the presence of germline mutation of the RET proto-oncogene. Ultrasonography and CT scan showed no tumor in the thyroid gland and blood samples showed normal levels of calcitonin and CEA. The calcitonin challenge test was negative. She is being carefully and regularly observed in the outpatient clinic.
Family member 5 (Fig. 1; IV-2)
No screening examination has so far been performed of this 7-year-old male, the grandson of the proband, owing to the absence of the mutation of the RET proto-oncogene mutation.
Genetic Studies
All subjects gave informed consent for mutation analysis of the RET proto-oncogene. Serum samples were frozen at –20°C until DNA extraction. Genomic DNA was extracted from whole blood of the proband and his family members and subjected to mutational analysis for the RET proto-oncogene as described previously (7). First, the analysis was performed for proband using polymerase chain reaction–single strand conformation polymorphism (PCR–SSCP) and direct sequencing, resulting in the presence of a codon 618 mutation (TGCCGC) (Fig. 4). The mutation, which creates HhaI site (GCGC), was confirmed by digestion analysis with restriction enzyme HhaI. Screening for the presence of the codon 618 mutation in the family members was done by direct sequencing and digestion analysis with restriction enzyme HhaI (Fig. 5). Three patients with MTC and the 9-year-old family member exhibited missense mutations at codon 618 of the RET proto-oncogene (Table 1).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONCASE REPORTDISCUSSIONAcknowledgmentsREFERENCES |
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Approximately 30% of medullary thyroid carcinoma (MTC) arising from thyroid C cells is hereditary, which is divided into three clinically distinct entities: MEN-2A, familial MTC and MEN-2B. MEN-2A is a family with MTC and either pheochromocytoma or parathyroid disease or both. The MEN-2B form is the additional presence of Marfanoid habitus and multiple systemic neurinomas without parathyroid disease. Familial MTC syndrome is defined as families with a minimum of four members with MTC and without evidence of pheochromocytoma and parathyroid disease on screening of living affected and at-risk individuals (8). According to these classifications, we diagnosed our patients as familial MEN-2A.
The calcitonin provocation test was previously used for early detection of MTC in an affected patient through stimulation by either pentagastrin alone or a combination of calcium and pentagastrin (4). However, this test is associated with a high incidence of false-positive cases and it is often difficult to differentiate abnormal from borderline cases, especially in children. Another drawback of the test is that it is often used too late in the disease process as children with MTC have been found positive in the calcitonin test for the first time who already had microscopic MTC with distant metastasis (9,10).
On the other hand, the International RET Mutation Consortium (11) reported only four out of 203 MEN-2A kindred to be negative for RET mutation. The accuracy of the RET gene analysis for diagnosis of MEN-2A is very high, hence this assay seems to be suitable for the early diagnosis of MEN-2A gene carriers at the time prior to the development of tumors or symptoms. Early diagnosis may offer some help and overcome problems related to the late detection of tumors in other members of MEN-2A families (3). The mutations are found mainly within exons 10 and 11 in MEN-2A and FTMC and in exon 16 in MEN-2B (2,3). Genetic analysis in the present study was performed on all five first-degree relatives extending through three generations and revealed four RET gene carriers and one non-carrier. This single base alteration was considered to be a pathological mutation because three of the four carriers had phenotype of MEN-2A syndrome. Identification of these mutations allowed early treatment of the carrier at a younger age, in anticipation of a reduction in MTC-related morbidity and mortality. Moreover, a negative result also frees non-carriers from regular examinations for MEN-2A. Recent studies have demonstrated the phenotype–genotype relationship in patients with multiple neoplasm syndrome type 2 (7). Further analysis and accumulation of the data will provide a better understanding of the long-term clinical outcome in these patients and, hence, help in clinical decision making with respect to the most suitable age for surgery and priority of surgical treatment in patients with MEN-2A.
MEN-2A is characterized by the presence of MTC in almost 100% of gene carriers (4), which influences the mortality in these patients. Therefore, many investigators advocate prophylactic thyroidectomy for gene carriers. However, the age at which such treatment should be conducted is still debatable. For example, Wells et al. (12) and Gill et al. (9) suggested thyroidectomy without lymph node dissection at 5 years of age in carriers diagnosed by molecular genetic tests, because none of the carriers in this group had positive nodes. However, other groups have argued against such early thyroidectomy, citing possible anesthesia-related complications, hypoparathyroidism, possible damage of the recurrent laryngeal nerve and hypothyroidism (4). Lips et al. (3) recommended postponement of total thyroidectomy until the age of 12 or 13 years to avoid the aforementioned risks. Other investigators advocated prophylactic thyroidectomy at 2 years of age in childhood MEN-2A, because a number of patients showed an advanced stage MTC at first surgery (5). Egawa et al. (7) reported that codon 618 mutation of RET gene is associated with a slow growth of MTC and recommended surgery only after 20 years of age, compared with other hot spots of codon 634 and 918 mutations. Considered together, the above studies indicate that further investigation is warranted to define the phenotype–genotype relationship and evaluate the histological and prognostic significance of prophylactic surgery. These steps may allow standardization of the appropriate timing and type of surgery for individual genotypes. We believe it is also important to classify the aggressiveness of MTC according to age and genotype.
The 9-year-old granddaughter (family member 4) in this family is being carefully monitored at the time of preparation of this report to determine the appropriate timing of thyroidectomy. Such surgery has not been conducted yet because of the potential risks of complications associated with thyroidectomy, the lack of radiological signs of development of MTC and possible slow growth of MTC associated with codon 618 mutation.
In conclusion, we have reported the clinical phenotype of one MEN-2A family with codon 618 (CysArg) of RET proto-oncogene, which is rarely reported. We have also reported the successful management of MEN-2A patients at an early age relative to their parents.
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Acknowledgments |
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TOPABSTRACTINTRODUCTIONCASE REPORTDISCUSSIONAcknowledgmentsREFERENCES |
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This research was supported in part by a Grant-in-Aid from the Ministry of Health and Welfare for the Second-term Comprehensive 10-year Strategy for Cancer Control and by Grants-in-Aid for Cancer Research (8–33 and 10–28) from the Ministry of Health and Welfare.
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FOOTNOTES |
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+ For reprints and all correspondence: Masafumi Kataoka, First Department of Surgery, Okayama Medical School, 2–5–1 Shikata-Cho, Okayama, Okayama 700-8558, Japan. E-mail: mkataoka@med.okayama-u.ac.jp
Abbreviations: MEN-2, multiple endocrine neoplasia type 2; MTC, medullary thyroid carcinoma; FMTC, familial medullary thyroid carcinoma; CT, computed tomography; MIBG, m-iodobenzylguanidine; PCR–SSCP, polymerase chain reaction–single strand conformation polymorphism
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REFERENCES |
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TOPABSTRACTINTRODUCTIONCASE REPORTDISCUSSIONAcknowledgmentsREFERENCES |
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1 Gardner DG. Recent advances in multiple endocrine neoplasia syndromes. Adv Intern Med 1997;42:597–627.[Web of Science][Medline]
2 Mulligan LM, Kwok JB, Healey CS, Elsdon MJ, Eng C, Gardner E, et al. Germ-line mutations of the RET proto-oncogene in multiple endocrine neoplasia type 2A. Nature 1993;363:458–60.[Medline]
3 Lips CJ, Landsvater RM, Hoppener JW, Geerdink RA, Blijham G, van Veen JM, et al. Clinical screening as compared with DNA analysis in families with multiple endocrine neoplasia type 2A. N Engl J Med 1994;331:828–35.
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11 Eng C, Clayton D, Schuffenecker I, Lenoir G, Cote G, Gagel RF, et al. The relationship between specific RET proto-oncogene mutations and disease phenotype in multiple endocrine neoplasia type 2. International RET mutation consortium analysis. J Am Med Assoc 1996;276:1575–9.
12 Wells SA Jr, Chi DD, Toshima K, Dehner LP, Coffin CM, Dowton SB, et al. Predictive DNA testing and prophylactic thyroidectomy in patients at risk for multiple endocrine neoplasia type 2A. Ann Surg 1994;220:237–50.[Web of Science][Medline]
Received August 30, 2000; accepted January 10, 2001.
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