Initial Diagnosis of Hematologic Malignancies Identified Through Thyroid Fine‐Needle Aspiration

ABSTRACT Introduction Fine‐needle aspiration (FNA) of the thyroid is crucial in diagnosing thyroid malignancies. While secondary malignancies involving the thyroid constitute only a minority of cases, results from thyroid FNA can offer the initial insight into a systemic process. This retrospective study aims to investigate first‐time diagnoses of hematologic malignancies diagnosed by thyroid FNA within our institution in the past 4 years. Methods We performed a retrospective review of first‐time hematologic neoplasm diagnoses in our pathology database at the University of Colorado Hospital. A total number of 3747 thyroid FNAs were performed during the four‐year period. Malignant categories with hematologic neoplasms were chosen for a thorough chart review. Cases of thyroidal involvement by previously diagnosed systemic hematologic neoplasms were excluded. For this study cohort, demographic data and clinicopathologic findings such as age, clinical impression, final cytologic diagnosis, presence of rapid on‐site evaluation (ROSE), and additional ancillary testing for every case were collected. Results The study included nine cases (four males and five females) with a mean age of 53 ± 14.46 years (range: 27–75 years). Five cases had a history of prior thyroid FNA with no definitive diagnosis. ROSE was performed in each of the nine cases. Five cases of diffuse large B‐cell lymphoma (DLBCL), one case of low‐grade follicular lymphoma (FL), one case of plasma cell myeloma, one case of Langerhans cell histiocytosis (LCH), and one case of chronic myeloid leukemia (CML) were identified on thyroid FNA. Several patients were at a high stage of disease with systemic involvement at presentation. The patients were treated with chemotherapy (DLBCL, FL, and plasma cell myeloma cases) or targeted therapy (LCH and CML cases). Conclusions Hematolymphoid malignancies involving the thyroid gland are challenging to diagnose as they are rare and may mimic other primary thyroid malignancies. However, we find that the thyroid can be the initial and sometimes the only site of presentation of a hematologic malignancy. Thorough cytomorphologic assessment, collaboration with hematopathologists, and ROSE are valuable tools for ensuring appropriate initial testing and facilitating timely, accurate diagnoses.