An algorithmic approach to overcome diagnostic challenges in FNAC in large-cell poorly differentiated thyroid...

Area of Science:

• Endocrinology
• Cytopathology
• Oncology

Background:

• Poorly differentiated thyroid carcinoma (PDTC) is a rare thyroid cancer with intermediate prognosis, defined by Turin criteria.
• Literature on PDTC histological features is available, but cytological descriptions, especially for the large cell type, are lacking.
• This study focuses on the cytological and clinical characteristics of PDTC with large cells (PDTC-LC) and abundant cytoplasm.

Purpose of the Study:

• To describe the cytological and clinical features of PDTC-LC.
• To identify potential diagnostic challenges in FNAC of PDTC-LC.
• To emphasize the importance of accurate FNAC diagnosis for patient management.

Main Methods:

• Retrospective analysis of 12 PDTC cases with abundant cytoplasm from 2007-2016.
• Review of fine-needle aspiration cytology (FNAC) smears for cytological patterns.
• Correlation of cytological findings with clinical data, including metastasis.

Main Results:

• Cases predominantly affected women (mean age 54.3 years) with a mean tumor size of 4.3 cm.
• FNAC smears showed scattered large cells with abundant cytoplasm, admixed with microfollicular and insular patterns.
• Metastasis to lymph nodes and distant sites (bone, visceral organs) occurred in 7 out of 12 cases.

Conclusions:

• The microfollicular pattern in PDTC-LC can be mistaken for differentiated follicular neoplasms on FNAC.
• Dissociated large cells may mimic Hürthle cell neoplasms.
• Accurate identification of PDTC-LC on FNAC is crucial for appropriate patient management, though immunocytochemistry may not be helpful in differentiating from Hürthle cell neoplasms but can help rule out medullary thyroid carcinoma and metastases.