Abstract
Poorly differentiated thyroid carcinomas (PDTCs) are a rare subtype of thyroid carcinomas that are biologically situated between well-differentiated papillary/follicular thyroid carcinomas and anaplastic thyroid carcinomas (ATCs).The diagnosis of conventional as well as oncocytic poorly differentiated thyroid carcinoma is difficult and often missed in daily routine. The current WHO criteria to allow the diagnosis of PDTCs are based on the results of a consensus meeting held in Turin in 2006. Even a minor poorly differentiated component of only 10%of a given carcinoma significantly affects patient prognosis and the oncocytic subtype may even have a worse outcome. Immunohistochemistry is not much help and is mostly used to exclude a medullary thyroid carcinoma with calcitonin and to establish a follicular cell of origin via thyroglobulin staining.Due to the concept of stepwise dedifferentiation, there is a vast overlap of different molecular alterations like BRAF, RAS, CTNNB1, TP53 and others between different thyroid carcinoma subtypes. A distinctive molecular tumor profile is therefore currently not available.PDTCs have a unique miRNA signature, which separates them from other thyroid carcinomas. The average relapse free survival is less than one year and about 50% of patients die of the disease. Modern tyrosine kinase inhibitors offer in conjunction with powerful molecular diagnostic new chances in these difficult to treat carcinomas.
Highlights
Theodor Langhans described a malignant thyroid carcinoma in 1907, which he termed “rampantly goiter” or “wuchernde Struma” in German [30]. While this entity was well received in the German literature and textbooks [41], the term “poorlydifferentiated thyroid carcinoma” (PDTC) was first introduced by Granner and Buckwalter in the early 1960s to the English-speaking audience
2004 [13] and since it has been a recognized entity [33]. Both of the aforementioned groups recognized the concept of a thyroid tumor that is placed biologically between well-differentiated thyroid carcinomas like papillary thyroid carcinomas (PTC) or follicular thyroid carcinomas (FTC) with an excellent prognosis and the extremely aggressive anaplastic thyroid carcinomas (ATC; [36])
FTC follicular thyroid carcinomas, PTC papillary thyroid carcinomas, STI solid, trabecular, or insular growth, PD poorly differentiated, HPF high power field carcinomas, which corresponds to 240 new cases in Germany each year
Summary
Theodor Langhans described a malignant thyroid carcinoma in 1907, which he termed “rampantly goiter” or “wuchernde Struma” in German [30]. The two schools of thought remained: While one school placed more emphasis on the growth pattern of the lesion (trabecular, insular, or solid), the other group used typical features of high-grade lesions like atypia, tumor necrosis, or a high mitotic index [1, 12, 38, 44, 49, 54] It took another 20 years for this entity to be accepted and introduced in the World Health Organization (WHO) series of malignant human neoplasms in. Both of the aforementioned groups recognized the concept of a thyroid tumor that is placed biologically between well-differentiated thyroid carcinomas like papillary thyroid carcinomas (PTC) or follicular thyroid carcinomas (FTC) with an excellent prognosis and the extremely aggressive anaplastic thyroid carcinomas (ATC; [36]) Both groups offered significant different diagnostic approaches to allow for such a diagnosis. Single cell necrosis does not count, and it is essential to exclude tumor necrosis followed by fine-needle aspiration (FNA), which happens frequently especially in oncocytic nodules
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