Fine-needle aspiration biopsy of monophasic variant of spindle epithelial tumor with thymus-like differentiation of the thyroid: report of one case and review of the literature.
Spindle epithelial tumor with thymus-like differentiation (SETTLE) is a rare biphasic tumor of the thyroid with approximately 20 well-documented cases reported in the English literature. Although a monophasic variant of SETTLE is conceivable, the majority of the reported cases were truly biphasic tumors. A minimal amount of epithelial component was present in the reported cases of so-called spindle-cell predominant SETTLE. Here, we report an apparently monophasic case of SETTLE in a 16-yr-old girl, in which no epithelial cells were identified in either fine-needle aspiration biopsy (FNAB) or the subsequent hemithyroidectomy specimen. The FNAB smears were moderately cellular and composed of single and loosely grouped spindle cells with homogenous metachromatic material, which could be mistaken as amyloid, erroneously suggesting medullary thyroid carcinoma. The compact nodules of uniform spindle cells in histology sections raised the possibility of monophasic synovial sarcoma. The spindle cells stained positive for both cytokeratin and vimentin, but were negative for thyroglobulin and calcitonin as well as neuroendocrine markers, confirming the diagnosis of SETTLE.
Tong
Guo-Xia
GX
Department of Pathology, Columbia University Presbyterian Hospital, New York, NY, USA. gt2125@columbia.edu
Hamele-Bena
Diane
D
Wei
Xiao-Jun
XJ
O'Toole
Kathleen
K
D000293:Adolescent; D044963:Biopsy, Fine-Needle; D002454:Cell Differentiation; D005260:Female; D006801:Humans; D009375:Neoplasms, Glandular and Epithelial / Q000473:pathology*; D013950:Thymus Gland / Q000473:pathology*; D013961:Thyroid Gland / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000473:pathology*