Hyperplasia is the excessive production of cells in otherwise normal tissues. In this case, the cells are formed at or near the thyroid, and are referred to as parafollicular or C-cells. These cells release calcitonin and give rise to medullary thyroid carcinoma (MTC). (See Diagnostic Code: 7914 Neoplasm malignant, any specified part of the endocrine system)

Variants that may lead to MTC include:

• Sporadic Type - which accounts for 80% of MTC tumors, and occurs in scattered incidences that peak in the 6th to 7th decades of life, usually presenting with metastases to cervical lymph nodes.

• Familial Forms - which are genetic and make up the remaining 20% of cases. They result from three variants: multiple endocrine neoplasia (MEN-type 2a), involving pheochromocytoma (see Diagnostic Code: 7918 Pheochromocytoma [benign or malignant); and parathyroid adenomas, (MEN-type 2b), involving pheochromocytomas and ganglioneuromas, or (non-MEN type) that involves many tumors.

Patients may have an enlarging thyroid mass and low serum calcium levels causing hyperirritability of muscles or even seizure. In addition, there may be a family history of MEN, a personal history of pheochromocytoma, or no symptoms at all. See signs and symptoms for malignant neoplasms (Diagnostic Code: 7914 Neoplasms Malignant) and pheochromocytoma (Diagnostic Code: 7918 Pheochromocytoma).

In the rare person with medullary cancer that stems from C-cell hyperplasia, calcitonin-related peptides and calcitonin levels are elevated. In addition, x-ray may reveal calcifications of the neck and lymph nodes.

Generally, treatment is to remove the tumor. A more complete thyroidectomy is usually indicated in follicular carcinoma because of the possibility of spread to the lymph nodes. If tumors are inoperable, palliative care is indicated or treatment or both, e.g., chemotherapy and radiotherapy are instituted to control progression.

There may be metastases via circulation of blood and lymphatics to other areas of the body. In addition, thyroidectomy may result in nerve damage to the recurrent laryngeal nerve, tetany, and thyroid storm that may progress to more serious conditions, e.g., delirium, coma, cardiovascular collapse, and death.

• Consider service connection on a presumptive basis as a chronic condition (38 CFR §3.307; §3.309 (a)). 

• Consider service connection on a presumptive basis as a condition associated with ionizing radiation exposure (38 CFR §3.307; §3.309 (d); §3.311 (b)).

None.