BACKGROUND: Fine-needle aspiration (FNA) sensitivity in discriminating between phyllodes tumor and its benign mimicker fibroadenoma (FA) remains low. Because a preoperative categorization of phyllodes tumor is crucial for their appropriate management, the authors undertook this study in an effort to improve the outcome of FNA by identifying reliable distinguishing features. METHODS: FNA smears from 15 and 12 histologically proven cases of phyllodes tumor and FA, respectively, were reviewed. The stromal and epithelial components were qualitatively and quantitatively analyzed. A group of cytological features that may distinguish between phyllodes tumor and FA were identified. Their value and reproducibility in categorizing phyllodes tumor cases were tested. RESULTS: Three major cytological features were exclusively seen in all of, or the vast majority of, the phyllodes tumor cases; fibromyxoid stromal fragments with spindle nuclei (90%), fibroblastic pavements (93%), and appreciable number of spindles cells of fibroblastic nature among dispersed cell population (100%). The identification of these features improved the pickup rate of phyllodes tumor from 40% to 100% and had substantial (j ¼ 0.56-0.73) interobserver and almost perfect (j ¼ 0.83) intraobserver reproducibility. There was no significant difference in the epithelial component characteristics between phyllodes tumor and FA. The frequency and degree of atypia in the dispersed cell population correlated well to the histological grade of phyllodes tumor. CONCLUSIONS: FNA has proven to be a reliable test in differentiating between phyllodes tumor and FA with high sensitivity and good reproducibility. The importance of training and continuing education is emphasized. Cancer (Cancer Cytopathol) 2010;118:33-40.

Our objectives were to study the types and incidence of thyroid follicular lesions coexisting with Hashimoto's thyroiditis (HT), the pitfalls in their cytodiagnosis, and the effect on management. All cases of HT diagnosed by fine-needle aspiration (FNA) and/or histology over a 7-yr period were retrospectively studied. HT coexisted with follicular adenoma (FA) in 6 cases, follicular variant of papillary carcinoma (FVPC) in 1 case, and goitrous nodule (GN) in 2 cases. The overall incidence rates of thyroid neoplasm and goitrous nodules coexistent with HT were 15% and 3.5%, respectively. A preoperative FNA diagnosis was available in 10 histologically proven cases of HT. A false-positive diagnosis of follicular neoplasm (FN) that led to unnecessary thyroidectomies was given in 3 cases. In 2 of these, the cytological diagnosis was HT with the possibility of coexisting FN, and in the third case, the cytological finding of HT was misinterpreted as FN. The main causes of these diagnostic pitfalls were the presence of hyperplastic follicular cells with nuclear pleomorphism, a paucity of lymphoid cells in burned-out HT, and lack of ones exposure. Nuclear pleomorphism was observed in none of the follicular adenomas. FNA diagnosed accurately the coexisting lesions in 6 cases; 3 FA, 1 FVPC, and 2 GN, but it did not sample HT. In one case, FNA diagnosed correctly both HT and the coexisting FA. Therefore, the presence of a coexistent neoplasm or goitrous nodule reduced the chances of sampling HT by 85.7%, with no false-negative results. Indeed, aspiration on and around the thyroid nodule helps in sampling HT. However, HT may dominate the smear and obscure neoplasia. This can be avoided if the procedure is performed by the pathologist and the aspiration is done on the nodule only. The overlapping cytological features of FN and HT were the main causes of false-positive results. This can be reduced by avoiding the diagnosis of FN in the presence of follicular-cell pleomorphism and/or moderate to excessive numbers of lymphoid cells, provided proper aspiration technique is maintained.

FNA was a highly sensitive method for the diagnosis of fibroadenoma. Current cytological criteria were reliable and gave high inter- and intra-observer reproducibility.

Fine needle aspiration (FNA) cytology plays a major role in the diagnosis of the thyroid lesions in university hospitals and tertiary referral institutions. Our aim was to find out if this was possible in small district hospitals with limited resources. Over a 7-year period, from October 1994 to April 2002, 303 patients with thyroid swellings underwent FNA with an overall adequacy rate of 97.7%. FNAs were performed specifically by the pathologists, so that our inadequacy rate, 2.3% was far lower than 11-29% reported elsewhere. The FNA findings were compared with subsequent histology results in 67 cases. The diagnosis of benign and neoplastic lesions was predicted accurately by FNA in 93% and 94.7% of cases, respectively. The latter reached 100% if results of FNA in follicular neoplasms were excluded. Sensitivity and specificity were 85.6% and 97.6%, respectively, which is comparable with results from tertiary institutions. The commonest thyroid lesions in our hospital were nodular goitre (52.4%), followed by thyroiditis (17.6%) and neoplasia (13.9%). We conclude that, with the availability of appropriate personnel, FNA is feasible as the major modality in district general hospitals. FNA in follicular lesions remains challenging but could be overcome in part by recognizing the criteria to differentiate follicular variant of papillary carcinoma and other follicular proliferations. Aspiration, smearing, staining and interpretation should be left to pathologists or other well-trained personnel to ensure good quality and consistency.

Differentiation between benign and malignant follicular lesions is one of the difficult diagnostic areas in thyroid fine needle aspiration (FNA). Nuclear criteria are usually used to distinguish between them. In this study the microarchitectural pattern of common benign follicular lesions, namely nodular hyperplasia (NH) and follicular adenoma (FA) were analysed in comparison with those of follicular variant of papillary carcinoma (FVPC) in order to aid in their differentiation. The FNA smears of histologically proven cases of FVPC, NH and FA were reviewed and compared. The microarchitectural features of FVPC, NH and FA were described. Three cytological features--multi-layered rosettes, branching monolayered sheets and balls of thick pinkish colloid--were exclusively observed in FVPC. Hyperplastic papillae with intact follicles and colloid were frequently seen in NH, 83% and 100%, respectively. Albeit less frequently, they were also noted in FVPC, 25% and 75% of cases, respectively. These overlapping features make the distinction between FVPC and NH sometimes difficult; however, assessing the smears for the specific features of FVPC may help in their differentiation. None of the aforementioned microscopic findings with the exception of the seldom presence of colloid were documented in FA. The crowded clusters of follicular cells were seen both in FA and FVPC; however, they were complex and branching in the latter and round to oval in the former. Finally, smears with good recovery of material are indispensable for the identification of these helpful microarchitectural patterns.