No abstract

The relationship between histologic type and survival of 258 thyroid malignancies has been analysed. A new clinicopathologic entity, poorly differentiated carcinoma of the thyroid, is proposed. Papillary and follicular carcinomas of the thyroid showed no significant difference in survival rates. Both tumors were histologically separated into well differentiated and poorly differentiated carcinomas, so that thyroid cancer, deriving from follicular cells, was divided into well differentiated, poorly differentiated, and anaplastic carcinomas. The characteristic histology of poorly differentiated carcinoma was the presence of solid, trabecular and/or scirrhous patterns. Poorly differentiated carcinoma was found in 13.6% of all thyroid malignancies, and its prognosis was worse than that of well differentiated carcinoma. The differences of survival rates among well differentiated, poorly differentiated and anaplastic carcinomas were statistically significant. Prognostic data support the suggestion that the clinicopathologic entity of poorly differentiated carcinoma is of value in determining management and survival of thyroid cancer patients.

Although anaplastic thyroid carcinoma (ATC) is one of the most aggressive malignancies, a few patients survive for a fairly long time after modern intensive treatment. We tried to identify prognostic factors of ATC to assist in deciding on the proper therapeutic strategy in individual patients. Of 47 patients with ATC (1976-1999), 3 patients with "incidental" ATC (largely differentiated thyroid carcinoma with a small region of ATC) were excluded because they had a favorable outcome. The 1-year survival rate of the remaining 44 patients with clinically distinct ATC was 16%. The presence of acute symptoms, large tumor (> 5 cm), distant metastasis, and leukocytosis (white blood cell count > or = 10,000/mm3) proved to be significant risk factors. Multivariate analysis by the Cox proportional hazard model showed that these four factors were independent factors for predicting death from ATC. We devised a novel prognostic index (PI) based on the number of these four unfavorable characteristics the patient possessed. Patients with a PI of < or =1 had a 62% survival rate at 6 months, whereas no patients with a PI of > or =3 survived longer than 6 months. All patients with a PI of 4 died from their disease within 3 months. Nine patients received multimodal treatment with a combination of surgery, external irradiation, and chemotherapy and had a long survival (mean 333 +/- 68 days; one patient is still alive and tumor-free), with a mean PI of 0.6. Our PI is useful as a means of selecting patients for aggressive therapy. When the PI is low, multimodal treatment should be attempted to obtain the best survival results; if it is high most patients are too seriously ill to tolerate intensive treatment and palliative therapy is recommended.

Clinicopathologic findings on small thyroid carcinomas measuring 10 mm or less in diameter were analyzed in 78 thyroidectomied cases. The authors divided small thyroid tumors into two subgroups according to diameter: 0 less than or equal to 5 mm (classified as minute carcinoma) and 5 less than 0 less than or equal to 10 mm (classified as tiny carcinomas). Characteristics including sex, age, histologic type, extrathyroid invasion, and lymph node metastasis were examined in each subgroup. In patients with minute carcinoma, very few incidences of extrathyroid invasion and lymph node metastasis were found. However, these involvements, especially lymph node metastasis, were found more frequently in patients with tiny carcinoma. The incidence of cervical lymph node metastasis was 13% in minute carcinoma and 59% in tiny carcinoma. (P less than 0.01). These findings suggest the need for more careful observation and treatment of tiny carcinomas, especially with respect to lymph node metastasis. In accordance with World Health Organization (WHO) classification, the histologic types of thyroid carcinoma were classified into papillary and follicular carcinomas. The papillary carcinoma and follicular carcinoma ratios were compared between the two subgroups. The discovery rate of follicular carcinoma was significantly higher in minute carcinoma than in tiny carcinoma (P less than 0.005). This suggests that the papillary carcinoma/follicular carcinoma ratio (p/f) increases as the size of the carcinoma increases, and that follicular carcinoma is the "seed," or initial form, of thyroid cancer. The female-male ratio in small thyroid cancer suggests that there is no sex difference in carcinogenesis but that there is more probability for cancer development in the thyroid in women.

Squamous differentiation of thyroid carcinoma was studied clinicopathologically and immunohistochemically i n 29 autopsy cases. Tumor cell nests with squamous differentiation (CNSD), which histologically resembled squamous cell carcinoma, were found i n 6 cases (20.7%). All of these 6 cases with CNSD had areas of undifferentiated carcinoma, representing 31.6% of 19 cases with undifferentiated carcinoma, and all but one case also showed coexisting papillary carcinoma. The CNSD were histologically associated with undifferentiated carcinoma in 5 cases, and with papillary carcinoma in one case; the CNSD were occasionally intermingled with these types of carcinoma, and there were findings suggesting a histological transition between the CNSD and undifferentiated carcinoma or papillary carcinoma. lmmunohistochemistry revealed that all the CNSD were reactive with antibodies for keratin and vimentin, whereas thyroglobulin and desmin were not expressed. It was concluded that the CNSD examined here were most probably due to extensive squamous differentiation (squamous metaplasia) i n undifferentiated carcinoma and papillary carcinoma. I n addition, the present results may explain the fact that cases diagnosed solely as squamous cell carcinoma sometimes show a prognosis similar to that of undifferentiated carcinoma, and may well represent extensive squamous differentiation i n such tumors rather than true squamous cell carcinoma of the thyroid. Acta Pathol Jpn 39: 306 -312, 1989.