Fine needle aspiration biopsy for the diagnosis of thymoma metastatic to the breast: a case report.
BACKGROUND
Extrathoracic metastases of thymomas are extremely rare, with only 9 documented cases in the cytologic literature, and a thymoma metastasis to the breast has not been reported before. Here we report the cytologic findings on fine needle aspiration biopsy (FNAB) for the diagnosis of a case of thymoma metastatic to the breast.


METHODS
A 73-year-old woman presented with a palpable mass in the right breast. A sonogram revealed a discrete, hypoechoic nodule in the upper inner quadrant of the breast. She had a history of mediastinal thymoma 2 years earlier, which was treated with chemotherapy because of inoperability. FNAB was performed: the cytologic specimen showed epithelial cell clusters with a few entrapped lymphocytes, suggestive of metastatic thymoma. However, the differential diagnosis also included a primary malignancy such as poorly differentiated ductal carcinoma or medullary carcinoma of the breast. Excisional biopsy with additional immunohistochemical staining confirmed the thymoma metastasis.


CONCLUSIONS
An FNAB-based diagnosis of this rare entity can be an appropriate, simple and minimally invasive procedure in the right clinical setting and with the appropriate patient history.
Department of Pathology, Chung-Ang University College of Medicine, Seoul, Republic of Korea.
Gui Young
GY
Kwon
Soon Auck
SA
Hong
Min Eui
ME
Hong
Eon Sub
ES
Park
Jae Hyung
JH
Yoo
Tae Jin
TJ
Lee
D000368:Aged; D044963:Biopsy, Fine-Needle; D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology / Q000556:secondary*; D017809:Fatal Outcome; D005260:Female; D006801:Humans; D013945:Thymoma / Q000175:diagnosis* / Q000473:pathology*; D013950:Thymus Gland / Q000473:pathology*; D016217:Ultrasonography, Mammary