Spindle epithelial tumor with thymus-like differentiation (SETTLE) of the thyroid.
BACKGROUND
Tumors of the so-called intrathyroidal epithelial thymoma type are a rare group of thyroid neoplasm tumors. Of this type of tumor, spindle epithelial tumor with thymus like differentiation (SETTLE) has been reported only 17 times in English literature.


METHODS
An 18-year-old woman was initially seen with a 6-cm left thyroid mass that was resected with a left thyroidectomy. Histopathologic features of the excised left thyroid tumor together with an immunohistochemistry and electron microscopy led us to a diagnosis of SETTLE.


RESULTS
Most of the specimen was composed of highly cellular spindle cells that formed intersecting and streaming fascicles. The spindle cells showed both vimentin immunoreactivity and cytokeratin immunoreactivity but no immunoreactivity for thyroglobulin or calcitonin. Electron microscopic examination of the spindle cells demonstrated prominent cytoplasmic tonofilaments, desmosomes, and basal lamina consistent with epithelial cell origin. DNA content analysis by flow cytometry revealed DNA diploidy.


CONCLUSIONS
SETTLE of thyroid gland is an extremely rare entity. A review of the literature reveals that SETTLE has distinctive morphologic features and an immunohistochemical profile.
Iwasa
Kazunori
K
Department of Surgery, Kouseiren Namerikawa Hospital, 119 Tokiwamachl, Namerikawa, Toyama, 9368585 Japan. tomkazu@mx1.fctv.ne.jp
Imai
Miwa Akasofu
MA
Noguchi
Masakuni
M
Tanaka
Shigehiro
S
Sasaki
Tadashi
T
Katsuda
Shogo
S
Kawahara
Ei
E
Mizukami
Yuji
Y
D000293:Adolescent; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007633:Keratins / Q000032:analysis; D009375:Neoplasms, Glandular and Epithelial / Q000473:pathology* / Q000601:surgery / Q000648:ultrastructure; D011379:Prognosis; D013950:Thymus Gland / Q000473:pathology* / Q000601:surgery / Q000648:ultrastructure; D013964:Thyroid Neoplasms / Q000473:pathology* / Q000601:surgery / Q000648:ultrastructure; D014746:Vimentin / Q000032:analysis
D014746:Vimentin; D007633:Keratins