J Pathol Transl Med.  2018 Jul;52(4):252-256. 10.4132/jptm.2018.04.28.

Hyalinizing Trabecular Tumor of the Thyroid Gland, a Diagnostic Challenge in Fine-Needle Aspiration Cytology: Case Report

• Rhee YY
• Jung HK
• Kim SH
• Kim SH

• KMID: 2417811
• DOI: http://doi.org/10.4132/jptm.2018.04.28

Abstract

Hyalinizing trabecular tumor (HTT) is a rare thyroid tumor with low to minimal malignant potential. HTT is often misinterpreted as other thyroid tumors, including papillary thyroid carcinoma (PTC) and medullary thyroid carcinoma (MTC), on fine-needle aspiration (FNA) cytology, because of its overlapping cytologic features, such as nuclear grooves and intranulcear pseudoinclusions. Although cytopathologists cannot definitely conclude HTT by FNA cytology, suspicion of HTT is necessary to avoid misdiagnosing HTT as PTC or MTC and to avoid unnecessary aggressive treatment. Here, we report a case of HTT with novel cytologic features in CellPrep liquid based cytology that was diagnosed as suspicious for papillary carcinoma by FNA and finally diagnosed as HTT in the surgical specimen.

Keyword

Hyalinizing trabecular tumor; Thyroid gland; Liquid-based cytology

MeSH Terms

Biopsy, Fine-Needle*
Carcinoma, Papillary
Hyalin*
Thyroid Gland*
Thyroid Neoplasms

Figure

• 

  Fig. 1. Radiologic findings. (A) Ultrasonography shows a 0.6 cm hypoechoic nodule in the left lobe (longitudinal). (B) Computed tomography reveals a 0.6 cm low density nodule with no evidence of extracapsular invasion and no significant lymph node enlargement.

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  Fig. 2. Gross specimen, microscopic findings (hematoxylin and eosin), and immunohistochemical staining of Ki-67 in the surgical specimen. (A) Gross specimen showing well circumscribed yellow to tan mass. (B, C) Histologic image shows trabecular pattern with oval to elongated tumor cells and intratrabecular hyalinization. (D) Ki-67 immunostaining using MIB1 monoclonal antibody shows characteristic peripheral membranous and cytoplasmic staining.

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  Fig. 3. Liquid based cytology (LBC; CellPrep) findings of hyalinizing trabecular tumor (HTT) (Papanicolaou). Cohesive aggregates or syncytial fragments of tumor cells around hyaline material. (A, B) Although oval to polygonal and occasionally elongated spindle-shaped tumor cells shows enlarged nuclei with hyperchromasia and occasional intranuclear pseudoinclusion as in papillary carcinoma, tumor cells in HTT shows dispersed fine chromatin rather than pale and clear chromatin, and had infrequent nuclear membrane irregularity. (C, D) Tumor cells were arranged in a more stratified trabecular pattern than in papillary carcinoma. Columnar character of tumor cells is observed in peripheral rims of clusters.

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