Hürthle cell tumors: using molecular techniques to define a novel classification system.

Area of Science:

• Endocrinology
• Oncology
• Molecular Pathology

Background:

• Hürthle cell tumors (HCTs) present diagnostic challenges, particularly when lacking classic papillary thyroid carcinoma (PTC) features.
• Ret/PTC gene rearrangements are specific markers for PTC, leading to the expanded diagnosis of Hürthle cell PTC (HCPTC).
• This study hypothesizes distinct behaviors for HCPTCs (papillary-like) versus Hürthle cell carcinomas (HCCs) (follicular-like).

Purpose of the Study:

• To discuss Hürthle cell tumors (HCTs).
• To identify Hürthle cell papillary thyroid carcinomas (HCPTCS) using molecular techniques.
• To differentiate Hürthle cell neoplasms based on histopathological and molecular criteria.

Main Methods:

• Retrospective review of 56 Hürthle cell tumors (HCTs).
• Analysis of pathological specimens for ret/PTC gene rearrangements using immunohistochemistry and RT-PCR.
• Classification based on invasion and ret/PTC status: Hürthle cell adenoma (HCA), Hürthle cell carcinoma (HCC), and Hürthle cell papillary thyroid carcinoma (HCPTC).

Main Results:

• Of 56 HCTs, 21 were HCAs, 15 were HCCs, and 20 were HCPTCs.
• No HCAs or HCCs tested positive for ret/PTC rearrangements.
• Five of six patients with lymph node metastasis were in the HCPTC group, indicating molecular analysis correlates with biological behavior.

Conclusions:

• Hürthle cell neoplasms can be classified using both histopathological and molecular criteria.
• The subclassification into follicular (HCC) and papillary (HCPTC) variants identifies two distinct biological groups of malignant HCTs.
• Molecular detection of ret/PTC gene rearrangements is crucial for diagnosing HCPTC and understanding tumor behavior.