Diffuse sclerosing variant of papillary carcinoma of the thyroid. Report of three cases.

Three cases of an unusual diffuse sclerosing variant of papillary carcinoma were found among 370 consecutive malignant tumors of the thyroid gland retained in the surgical pathology files of Kanazawa University Hospital over the last 10 years. The tumors were characterized by diffuse involvement of one or both lobes of the thyroid, dense fibrosis, papillary carcinoma with marked squamous metaplasia and abundant psammoma bodies, heavy lymphocytic infiltration and extensive lymphatic permeation. In two cases, the neoplasms showed more aggressive regional lymph node metastases and local invasion; the patient in the first case underwent surgery three times after initial radical surgery because of regional lymph node recurrences, and the second case showed direct invasion of the thyroid tumor to the larynx and distant metastasis to the lungs. Although the number of examined cases was small, the findings suggest that the diffuse sclerosing variant type has a less favorable prognosis and should be differentiated from papillary carcinomas with excellent prognosis.