Important cytological findings for distinction between follicular variant and conventional papillary thyroid carcinoma, including noninvasive follicular thyroid tumors with papillary-like nuclear features

• Published in: Endocrine Journal Vol. 66; no. 5; pp. 475 - 483
• Main Authors: Koshikawa, Takashi, Fujita, Nao, Ueda, Nanae, Ota, Yuko, Sasaki, Eiichi, Murakami, Yoshiko, Hosoda, Waki, Yatabe, Yasushi, Hanai, Nobuhiro, Higuchi, Miyoko, Hirokawa, Mitsuyoshi, Miyauchi, Akira
• Format: Journal Article
• Language: English
• Published: Japan The Japan Endocrine Society 01.01.2019; Japan Science and Technology Agency
• Subjects: Adenocarcinoma, Follicular - diagnosis; Adenocarcinoma, Follicular - pathology; Adolescent; Adult; Aged; Aged, 80 and over; Chromatin; Colloids; Cytodiagnosis; Cytology; Diagnosis, Differential; Female; Fine-needle aspiration cytology; Follicular variant; Giant cells; Humans; Inclusion bodies; Invasiveness; Male; Middle Aged; Noninvasive follicular thyroid tumor with papillary-like nuclear features (NIFTP); Papillary thyroid carcinoma; Statistical analysis; Thyroid; Thyroid cancer; Thyroid Cancer, Papillary - diagnosis; Thyroid Cancer, Papillary - pathology; Thyroid Gland - pathology; Thyroid Neoplasms - diagnosis; Thyroid Neoplasms - pathology; Tumors; Young Adult; Follicular variant; Papillary thyroid carcinoma; Fine-needle aspiration cytology; Noninvasive follicular thyroid tumor with papillary-like nuclear features (NIFTP)
• DOI: 10.1507/endocrj.EJ18-0525
• ISSN: 0918-8959

We studied cytological specimens of conventional papillary thyroid carcinoma (PTC), follicular variant papillary thyroid carcinoma (FVPTC), and noninvasive follicular thyroid tumor with papillary-like nuclear features (NIFTP) (formerly noninvasive FVPTC) to identify useful cytological parameters for their differentiation. Cytological findings of invasive FVPTC and NIFTP were very similar to each other but differed from those of conventional PTC. Intranuclear cytoplasmic inclusions, true papillary cell clusters, monolayered cell sheets, ropy colloids, multinucleate giant cells, psammoma bodies, and cystic background were the observed characteristic features of conventional PTC. Microfollicular cell clusters and dense globules of colloids were characteristic features of invasive FVPTC and NIFTP. Scoring the eight parameters (intranuclear cytoplasmic inclusions, nuclear grooves, powdery chromatin, true papillary cell clusters, ropy colloids, multinucleate giant cells, psammoma bodies, and cystic background) readily distinguished NIFTP from conventional PTC, but could not distinguish NIFTP from invasive FVPTC. The average total score of NIFTP, invasive FVPTC, and conventional PTC were 2.60 ± 0.55, 2.63 ± 0.62, and 4.57 ± 0.99, respectively. The difference between conventional PTC and NIFTP or invasive FVPTC was statistically significant (p < 0.001, Student’s t-test). Individuals with more than three of the identified parameters likely harbor conventional PTC, rather than NIFTP. In this way, 87.5% (112/128) of conventional PTCs could be differentiated from NIFTP, and definitively diagnosed as malignant by cytology.