Thyroid cancer in familial adenomatous polyposis: A report of 14 cases

Objectives: Recent publications have reported that the histological picture of the thyroid cancers that occur in patients with familial adenomatous polyposis (FAP) is distinctive. The microscopic appearance of such cancers has been described as being sufficiently pathognomonic that FAP can be predicted in such patients prior to the development of colonic polyps. Methods: To test this hypothesis, fourteen cases of thyroid cancer in FAP patients were examined with particular attention to the histology of the neoplasms. Results: All fourteen patients were females, and the age range was 21 to 42 years old. Three patients had multiple thyroid tumors. Ten of the tumors were papillary carcinomas with papillae and distinctive nuclear changes, and they contained solid areas with peculiar aggregates of spindle cells alternating with other areas showing cribriform and trabecular patterns. Their microscopic appearance was very unlike that of ordinary usual papillary carcinomas. In one case the histological pattern mimicked follicular carcinoma, albeit an atypical one. Significantly, in six cases the diagnosis of thyroid cancer was established prior to the onset of colonic polyps. Conclusions: The histology of thyroid cancer in FAP patients is unique, and is sufficiently distinctive to suggest the presence of FAP before the onset of colonic polyps. Even if the prognosis is favorable, total thyroidectomy and regional nodal dissection are recommended.