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Cytopathology of insular carcinoma of the thyroid
Author(s) -
Guiter Gerardo E.,
Auger Ma,
Ali Syed Z.,
Allen Elizabeth A.,
Zakowski Maureen F.
Publication year - 1999
Publication title -
cancer cytopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.052
H-Index - 304
eISSN - 1097-0142
pISSN - 0008-543X
DOI - 10.1002/(sici)1097-0142(19990825)87:4<196::aid-cncr6>3.0.co;2-p
Subject(s) - cytopathology , medicine , pathology , thyroid , fine needle aspiration , thyroid neoplasm , thyroid carcinoma , atypia , differential diagnosis , nuclear atypia , follicular cell , carcinoma , metastatic carcinoma , cytology , biopsy , immunohistochemistry
BACKGROUND Insular carcinoma of the thyroid (ICT) first was reported in 1984. To the authors' knowledge, few cytology reports have been published since that time. The authors describe the cytologic features of six tissue‐proven ICTs and propose criteria that suggest its diagnosis. METHODS Four cases were thyroid fine‐needle aspiration (FNA) samples. Two cases were FNAs of metastases. All cases were found to be classic ICT on examination of primary or metastatic surgical specimens. RESULTS Three cases originally were diagnosed as carcinoma, including two FNAs of metastatic sites and one thyroid FNA. Two additional thyroid FNAs were diagnosed as suspicious for malignancy, favor follicular neoplasm. One case was termed a neoplasm, favor follicular type. Smears showed high cellularity and scanty colloid. Three cases were found to contain some microfollicles. One case showed a few papillae. Necrosis and mitosis were rare. Cells were round with pale, poorly defined cytoplasm. Nuclei were round and monomorphic with finely granular chromatin, mild hyperchromasia, smooth nuclear membranes, and small nucleoli. Nuclear grooves and inclusions were rare. CONCLUSIONS Three cases were diagnosed as suspicious for follicular neoplasm, the main differential diagnosis of ICT. Both tumors exhibited high cellularity and scanty colloid. However, ICT showed a predominance of single cells whereas follicular neoplasms reveal microfollicles with more nuclear atypia. There is cytologic overlap between these two neoplasms. Papillary thyroid carcinoma should be distinguished from ICT easily because the latter usually does not reveal the classic cytologic features associated with the former. ICT should be considered in the differential diagnosis of follicular neoplasms. Features favoring ICT are predominance of single cells, small loose nests of cells with few microfollicles, and little nuclear atypia. Cancer (Cancer Cytopathol) 1999;87:196–202. © 1999 American Cancer Society.