[Cytological diagnostic challenge: two hyalinizing trabecular tumor case reports]

Area of Science:

• Endocrinology
• Cytopathology
• Surgical Pathology

Background:

• Hyalinizing trabecular tumors (HTT) are rare thyroid neoplasms.
• Accurate preoperative diagnosis of HTT is challenging due to cytological similarities with papillary thyroid carcinoma (PTC).
• Similarities include nuclear overlapping, intranuclear inclusions, and nuclear grooves, leading to frequent misdiagnosis in preoperative cytology.

Observation:

• This study reports two cases of HTT initially diagnosed as PTC on preoperative cytology.
• Both patients underwent total thyroidectomy and lymph node dissection based on the initial misdiagnosis.
• A literature review was conducted to identify diagnostic criteria for improving HTT diagnosis in thin-layer cytology.

Findings:

• The fibrillar and hyaline material within cellular clusters of HTT is the most discriminating feature compared to PTC.
• However, identifying this material in thin-layer cytology remains challenging.
• Typical membranous and cytoplasmic MIB-1 immunostaining may aid diagnosis, but its utility in thin-layer smears requires further investigation.

Implications:

• Improved diagnostic criteria for HTT in thin-layer cytology are needed to reduce misdiagnosis rates.
• Distinguishing HTT from PTC preoperatively can prevent unnecessary extensive surgeries.
• Further research on MIB-1 immunostaining in thin-layer smears is warranted to enhance diagnostic accuracy for rare thyroid tumors.