Lymphocytic thyroiditis in fine-needle aspirates: differential diagnostic aspects

Area of Science:

• Pathology
• Cytopathology
• Endocrinology

Background:

• Lymphocytic thyroiditis encompasses several conditions, including Hashimoto's thyroiditis and focal thyroiditis.
• Accurate diagnosis of thyroiditis subtypes is essential for appropriate clinical management.
• Fine-needle aspiration (FNA) is a primary diagnostic tool for thyroid lesions.

Purpose of the Study:

• To evaluate the morphological criteria for diagnosing various types of lymphocytic thyroiditis in FNA samples.
• To differentiate Hashimoto's thyroiditis from focal thyroiditis, particularly when adjacent to thyroid neoplasms.
• To establish guidelines for surgical intervention in ambiguous cases.

Main Methods:

• Retrospective analysis of 950 thyroid FNA cases.
• Identification and classification of 121 cases with lymphocytic thyroiditis.
• Correlation of cytological findings with serological and histological data where available.
• Assessment of diagnostic challenges in differentiating thyroiditis subtypes.

Main Results:

• Hashimoto's thyroiditis was readily diagnosed in FNA with adequate cellularity and oxyphilic cells.
• The fibrous variant of Hashimoto's thyroiditis presented diagnostic difficulties.
• Focal thyroiditis adjacent to neoplasms mimicked Hashimoto's thyroiditis, posing a diagnostic challenge.
• 121 out of 950 aspirates (12.7%) showed lymphocytic thyroiditis.

Conclusions:

• Morphological assessment in FNA is key for diagnosing lymphocytic thyroiditis.
• Distinguishing focal thyroiditis from Hashimoto's thyroiditis requires careful evaluation, especially in neoplastic contexts.
• Surgical exploration is recommended for severe lymphocytic thyroiditis with negative antibody titers to rule out neoplasm.