Review Question - QID 104392

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Thyroid Cancer QID: 104392 (M2.ON.14.67)

QID 104392 (Type "104392" in App Search)

A 28-year-old girl presents to clinic with a noted change in her voice and difficulty swallowing solids. On physical exam there is a palpable, nontender swelling in the front of her neck. There is no cervical lymphadenopathy. An ultrasound examination of the neck is shown in Figure A. After a non-diagnostic fine-needle aspiration biopsy of the mass, she is taken to the operating room for a hemi-possible total-thyroidectomy. Pathology of the specimen diagnoses this patient with medullary thyroid carcinoma. If this patient's cancer was secondary to an inherited germline mutation, what gene should be sequenced in this patient's family members?

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RAS

1/48

RET

88%

42/48

c-MYC

0/48

BRAF

1/48

NF2

2/48

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This patient has medullary thyroid cancer (MTC), which can be seen as part of multiple endocrine neoplasia (MEN) type 2. Appropriate screening in families of an affected person is genetic testing for the RET-proto-oncogene germline mutation.

Medullary thyroid cancer is derived from calcitonin-synthesizing C cells. As a result, the clinical presentation may be with hypocalcemia. 10-25% of the cases are familial and associated with MEN 2A or 2B as a result of a RET gene mutation, with the remaing medullary thyroid cancer cases are sporadic, with an important risk factor being previous irradiation to the neck.

Cohen discusses genodermatoses with malignant potential. Included genodermatoses are nevoid basal cell carcinoma syndrome, Cowden's disease, multiple endocrine neoplasia syndromes, neurofibromatosis, and Peutz-Jeghers syndrome, all of which have increased risk of malignancy in combination with skin abnormalities. In these conditions, appropriate evaluation of the patient's family potentially at risk, as well as genetic counseling, should be performed.

Cui et al. present a case of multiple endocrine neoplasia type 2A (MEN2A), a subtype of MEN2. MEN2A is characterized by MTC, pheochromocytoma, and primary hyperparathyroidism. They detected a RET gene mutation in 3 family members, including the proband. Elevated serum calcitonin level was present at initial presentation and all 3 members had medullary thyroid carcinoma.

Figure A demonstrates a solid mass on ultrasound in the right thyroid lobe.

Incorrect Answers:
Answer 1: RAS is a known oncogene but not inherited with MEN2/FMTC.
Answer 3: c-MYC is a known inducible stem cell linage driver and has no role in MEN2/FMTC.
Answer 4: BRAF mutations are seen with melanoma and papillary as well as follicular neoplasms but have no role in MEN2/FMTC.
Answer 5: NF2 mutations are seen in neurofibromatosis type 2.