Distinguishing the Tall Cell From Classic Subtypes of Papillary Thyroid Carcinoma on FNA: A Cytological and...

Tall cell subtypes of papillary carcinoma thyroid (T-PTC) are defined as tumour cells with a height: breadth ratio of > 3. The tall cell subtype of papillary thyroid carcinoma is known for its poor outcomes and aggressive nature. Its definitive preoperative recognition would be advantageous and would help the surgeon to plan a more effective treatment regimen. We aim to determine if the cytomorphological features are sufficiently characteristic to enable their distinction from classic subtypes of PTC on FNAC.

We compared the cytological features of 20 cases of histologically proven T-PTC with 20 cases of the classic PTC (C-PTC). The presence of tall cells (Height: breadth ratio > 3) was confirmed by image morphometry. Thirty-six parameters, pertaining to architectural, cytological, nuclear and background characteristics, were analysed using a semi-quantitative scoring system. The statistical significance of the data was determined using Fisher's probability test and Chi-square test.

Tall cells, spindle cells, tail-like cells, and isolated tumour cells were seen in a significantly higher number of cases of T-PTC than C-PTC (p value < 0.05). These features' sensitivity, specificity, PPV and NPV in identifying T-PTC range from 90% to 100% and approach 100% when all four features are present in a given case.

The cytomorphological characteristics of T-PTC are distinct. Key features distinguishing T-PTC from C-PTC include tall cells, spindle-shaped cells and tail-like cells with irregular nuclear contours.

These distinctive cytomorphological attributes can aid cytopathologists in differentiating T-PTC from the classic subtype during preoperative FNAC.