[Pathological and clinical features of malignant thyroid tumors: classification, immunohistology, prognostic criteria].

Abstract

In a retrospective analysis of 433 surgical specimens of malignant thyroid tumours, the prognostic efficiency of different morphological methods (conventional light microscopy, immunohistology, cytophotometric and flow cytometric DNA-estimations) was demonstrated. The clinical behaviour of the different forms of thyroid malignancy was predominantly determined by the histological type of neoplasia. High global values of significance were obtained when comparing the prognoses of follicular, papillary, medullary and anaplastic thyroid carcinomas as classified by the WHO. Their respective estimated survival curves are shown in Figure 37. As compared with the remaining thyroid carcinomas, papillary neoplasm altogether showed the significantly best long-term prognosis (p less than 0.001). Almost identical survival rates were recorded for patients with follicular and medullary carcinomas, which lay intermediate between the more favourable papillary and the in all cases fatal anaplastic tumours. Differences between these groups each time proved to be statistically significant (p less than 0.001). In addition, large differences also existed regarding the mode of tumour propagation for these carcinomas: papillary tumours usually showed lymphatic metastases while follicular carcinomas showed haematogenous spread. In contrast to the other types of carcinomas, medullary tumours frequently exhibited a prolonged clinical course. In the latter case, local recurrences were the most frequent cause of death, while patients with follicular carcinomas primarily died of distant blood-borne metastases. For the differentiated thyroid carcinomas the estimation of prognosis was improved by sub-typing the neoplasias according to their mode of growth. Encapsulated and occult papillary carcinomas and the majority of encapsulated follicular carcinomas showed an excellent biological behaviour. They should not be confused with the respective widely invasive tumours of follicular and papillary type and accordingly less aggressive surgical treatment should be employed. In addition, presence of oxyphilic cytodifferentiation was prognostically relevant among follicular and papillary carcinomas. The worse survival rate for such tumours could partly be explained by the lack of radioiodine uptake, this being caused by special ultrastructural features typical for these tumours. In contrast, the evidence of clear-cell differentiation was rather of differential diagnostic (in typing of metastatic renal cell carcinomas) than of prognostic value.(ABSTRACT TRUNCATED AT 400 WORDS)