Thyroid sarcoidosis: a rare entity in the differential diagnosis of thyroid cancer

SUMMARY: We present two cases of thyroid sarcoidosis that were misdiagnosed as thyroid cancer. In the first patient, fine needle aspiration cytology (FNAc) of a suspicious thyroid nodule indicated the presence of papillary thyroid cancer, and the patient underwent thyroid surgery. However, histopathology identified a sarcoid granuloma, without any sign of malignancy. The second patient had a history of papillary microcarcinoma with suspicious lymph nodes diagnosed years after the initial diagnosis and was referred for assessment of cervical lymphadenopathy. Fine needle aspiration cytology (FNAc) of the suspicious lymph nodes erroneously indicated metastasis from thyroid cancer, and lateral modified lymph node dissection was performed, based on FNAc and ultrasonographic features. Histopathology excluded malignancy and identified non-caseating granulomas. Sarcoidosis of the thyroid may have a clinical presentation similar to well-differentiated thyroid carcinoma and, although rare, should be considered in the differential diagnosis, especially when other signs of the disease are already present. In these cases, FNAc provided a false diagnosis of papillary thyroid carcinoma and lymph node metastases that led to unnecessary surgery. LEARNING POINTS: Sarcoidosis may share clinical and ultrasonographic features with papillary thyroid carcinoma. Fine needle aspiration cytology is helpful in the diagnosis of both conditions; however, the overlapping cytological characteristics may lead to erroneous diagnosis. The present cases illustrate the importance of cytological identification of these difficult cases. Every piece of information provided by the clinician is essential to the cytologist.