Fine needle aspiration biopsy features with histologic correlation in mediastinal hepatoid yolk sac tumor presenting with sternum metastasis: a case report.
BACKGROUND
The hepatoid variant of yolk sac tumor (H-YST) is an exceedingly rare and highly malignant neoplasm. We present and discuss our experience with cytologic and histopathologic features of a mediastinal H-YST presenting with sternum metastasis, which to the best of our knowledge has not been previously reported.


METHODS
A 38-year-old man presented with a large mass on the sternum. Computed tomography of the thorax showed a large anterior mediastinal mass with sternum metastsis and multiple lung metastases. Laboratory examination revealed elevated serum alpha-fetoprotein (60,000 IU/mL). No tumor was found in the other organ systems. A percutaneous fine needle aspiration biopsy and subsequent open surgical biopsy were performed on the sternum metastasis. Cytologically, the tumor was composed of monotonous, large, round to polygonal hepatoid cells forming solid sheets and trabeculae entrapped with endothelial cells resembling hepatocellular carcinoma. Histopathologic sections of tumor showed tumor cells with eosinophilic to clear cytoplasm arranged in a solid, trabecular growth pattern, with some acinar formations. Immunohistochemical study supported the hepatoid origin.


CONCLUSIONS
Fine needle aspiration cytology, together with the characteristic clinical presentations and specific tumor markers, is crucial to the initial diagnosis of H-YST.
Ceyhan
Koray
K
Division of Clinical Cytology, Department of Pathology, Faculty of Medicine, Ankara University, Turkey. korayceyhan@yahoo.com
Utkan
Güngör
G
Dincol
Dilek
D
Erdogan
Nural
N
Erekul
Selim
S
Umudum
Haldun
H
D000328:Adult; D000906:Antibodies; D044963:Biopsy, Fine-Needle; D018240:Endodermal Sinus Tumor / Q000473:pathology*; D042783:Endothelial Cells / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008479:Mediastinal Neoplasms / Q000473:pathology*; D008875:Middle Aged; D009362:Neoplasm Metastasis; D013249:Sternum / Q000473:pathology*; D000509:alpha-Fetoproteins / Q000378:metabolism
D000906:Antibodies; D000509:alpha-Fetoproteins