The clinical course after definitive operation for medullary thyroid carcinoma.

Thorough family studies that used the radioimmunoassay procedure for calcitonin (CT) during the past 12 years have provided data on 70 patients from 12 kindreds with hereditary medullary thyroid cancer (hereditary group) and 28 patients with sporadic or nonhereditary medullary thyroid cancer (sporadic group). Serum CT elevations after total thyroidectomy as evidence of residual tumor have been encountered in 21 of 25 patients in the hereditary group with palpable tumors preoperatively (84%) and in 13 of 24 in the sporadic group (54%). However, none of 26 patients with hereditary nonpalpable lesions found by family screening studies have been found to have postoperative CT elevations. Both cervical lymphadenectomy in patients with lymph node involvement at initial operation and reexploration in those with CT elevations after total thyroidectomy have been unsuccessful in the eradication of metastatic disease. These data emphasize the value of thorough family studies that use stimulated CT measurements in the detection of early and curable neoplasms. Involvement of the parathyroid glands or the adrenal medulla that occurred in the hereditary multiple endocrine neoplasia syndromes varied from family to family; it influenced the clinical course and required regular surveillance with calcium and catecholamine studies. Separation of hereditary from sporadic cases has practical value in the identification of family members at risk and also in the provision of prognostic data.

Phenotype mapping of the multiple endocrine neoplasia type II syndrome.

The multiple endocrine neoplasia (MEN) IIb syndrome has been differentiated from MEN IIa by the presence of various phenotypic characteristics such as mucosal neuromas, marfanoid habitus, congenital skeletal anomalies, and prominent corneal nerves, as well as the lack of parathyroid involvement. Analysis of a kindred with some characteristics of both syndromes (including an associated chromosomal deletion) tends to unify the MEN II syndromes as a single disorder with variable expressivity. The linear map of the genetic determinants is postulated to conform with the following phenotype order: parathyroid tumors, medullary thyroid cancer, pheochromocytomas, skeletal changes, prominent corneal nerves, mucosal neuromas, and marfanoid habitus. Appreciation of this sequence can allow earlier identification and treatment of affected individuals.

Pheochromocytoma in multiple endocrine neoplasia type II: an example of the two-hit theory of neoplasia.

Six kindreds in which pheochromocytomas were present as manifestations of the autosomal dominantly inherited multiple endocrine neoplasia (MEN) type II were studied. The patients underwent bilateral total adrenalectomy with the finding that the pheochromocytomas were bilateral, multifocal, and associated with distinct medullary hyperplasia and reduction in the normal corticomedullary ratio-- features not usually seen in patients with sporadic pheochromocytoma. These findings were exemplified in recent cases of a 34-year-old woman and a 40-year-old man who both had undergone total thyroidectomy for medullary carcinoma of the thyroid. Diagnoses of pheochromocytoma were made by catecholamine studies, computerized tomography, and 131I meta-iodobenzylguanidine (MIBG) scan. Bilateral adrenalectomy was performed with the finding of multiple bilateral pheochromocytomas and adrenal medullary hyperplasia. As in hereditary medullary carcinoma of the thyroid, the histologic findings in pheochromocytomas of the MEN II syndrome are consistent with Knudson's two-mutational-event theory for the initiation of neoplasia, with adrenal medullary hyperplasia representing the manifestation of the first or genetic mutational event and being present invariably in the hereditary cases.

Clinical characteristics distinguishing hereditary from sporadic medullary thyroid carcinoma. Treatment implications.

Distinctive differences between the hereditary and sporadic varieties of medullary thyroid carcinoma include the uniform bilaterality, consistent association of C cell hyperplasia, and the frequent association with other endocrine lesions as characteristics of the hereditary type. Total thyroidectomy is required for hereditary medullary thyroid carcinoma. Lateral cervical lymph node dissections do not appear necessary for the hereditary type when not palpable, detected only by family screening, and when biopsy of midjugular lymph nodes shows no evidence of metastasis. For palpable medullary thyroid carcinoma, the eradication of all cervical locations is unlikely to result in normal or undetectable levels of serum calcitonin postoperatively, even though such appears more likely for the sporadic variety.