Extramedullary hematopoiesis involving the thyroid: A rare cytologic finding in otherwise healthy patients and review of literature.

BACKGROUND/PURPOSE: The thyroid gland is an uncommon site for the presence of extramedullary hematopoiesis (EMH). We report the cases of four Taiwanese women with hematopoietic elements on the smears of thyroid fine needle aspiration (FNA) samples and compare the findings with those of previously reported cases.

METHODS

We retrieved the data of cases in which thyroid FNA performed between January 2000 and December 2016. The clinical manifestations, laboratory data, and image findings of cases with thyroid EMH were reported. A review of English literature was performed, and the reported cases were compared with our series.

RESULTS

During the study period, 63,361 specimens of thyroid FNAs were identified. Four specimens contained hematopoietic elements from four women. Ultrasound study revealed calcifications in three patients. A review of English literature yielded 18 reports of thyroid EMH involving 29 patients. Twenty-six patients were women, and three were men. Nodule calcifications were found in 13 patients. Four patients had primary myelofibrosis, and one had chronic anemia. None had a thyroid malignancy.

CONCLUSION

Four patients were noted to have bone marrow elements on the smears among 63,361 thyroid FNA samples. These four Taiwanese women presented with nodular goiter and foci of hematopoietic elements by thyroid FNA without any chronic disease of hematopoietic tissue or any evidence of a thyroid malignancy.