Recommendations for reporting C cell pathology of the thyroid.

BACKGROUND: Calcitonin screening programs have proved to be effective in early detection of medullary thyroid carcinoma, not only in patients with known risk factors for the development of hereditary tumors. Thus, more thyroidectomies, based on an abnormal pentagastrin test, can be expected. Here we give summarizing recommendations for reporting C cell pathology.

METHODS: All patients underwent total thyroidectomy and were tested for germ-line mutations in the RET-Protooncogene. The entire surgical specimens were blocked and C-cell disorders were assessed using conventional histology and immunohistochemistry.

RESULTS: Among 110 patients with an abnormal pentagastrin test, 60 (55%) had medullary thyroid carcinoma (T1 34% [n = 37], T2 14% [n = 16], T4 6% [n = 7]), and 50 (45%) had C cell hyperplasia only. C cell hyperplasia accompanying medullary thyroid carcinoma was found in 13 of 15 familial and in 28 of 45 sporadic patients. All C cell changes were found in the upper two thirds of the thyroid lobes and 83% of the medullary thyroid carcinomas could be identified with frozen sections.

CONCLUSION: 1. Abnormal pentagastrin stimulation is always associated with either medullary thyroid carcinoma or C cell hyperplasia. 2. Blocking of the entire upper two thirds of the thyroid lobes is essential for reliable detection of C cell hyperplasia and small medullary thyroid carcinomas. 3. Most medullary thyroid carcinomas can be detected with intraoperative frozen sections. 4. The presence of C cell hyperplasia should always be reported; however its usefulness for indicating familial risk is limited and its role as a preneoplastic condition in patients without RET-protooncogene mutations remains to be elucidated.