Follicular variant of papillary carcinoma of the thyroid. A cytologic study of 15 cases

Ultrasonographic Characteristics of the Follicular Variant Papillary Thyroid Cancer According to the Tumor Size

Follicular variant papillary thyroid cancer (FVPTC) is the second most common subtype after conventional PTC. We compared ultrasonographic (US) features of FVPTC to those of conventional PTC according to tumor size. We reviewed US findings, pathologic reports, and medical charts of 249 PTC patients with surgically proven disease (83 FVPTCs, 166 conventional PTCs) at our institution from January 2007 to December 2012. FVPTCs were divided into PTC-like and follicular neoplasm (FN)-like based on sonographic characteristics. PTC-like features were defined as having at least one malignant feature (taller-than-wide shape, infiltrative margin, marked hypoechogenicity, and micro-calcifications), whereas FN-like cancers showed oval solid features without malignant features. FVPTCs showed a higher rate of FN-like features than conventional PTCs. Of 166 conventional PTCs, 13 (7.8%) had FN-like features and 153 (92.2%) had PTC-like features, whereas of the 83 FVPTCs, 31 (37.3%) had FN-like features and 52 (62.7%) had PTC-like features. Macro-FVPTCs showed a higher rate of FN-like features than micro-FVPTCs (P < 0.001). Of 21 macro-FVPTCs, 18 (85.7%) had FN-like features and 3 (14.3%) had PTC-like features, whereas of the 62 micro-FVPTCs, 13 (21%) had FN-like features and 49 (79%) had PTC-like features. There were no differences in multifocality, extrathyroidal invasion, and lymph node metastasis between PTC-like FVPTCs and FN-like FVPTCs. FVPTCs showed fewer sonographic malignant features than conventional PTCs. In particular, FVPTCs larger than 1 cm had a more frequent benign sonographic appearance. Therefore, if fine-needle aspiration result is suspicious for PTC in a nodule larger than 1 cm with no suspicious US features, the possibility of FVPTC might be considered.

Clinical Presentations and Outcomes of Surgical Treatment of Follicular Variant of the Papillary Thyroid Carcinomas

BACKGROUND

The follicular variant of papillary thyroid carcinoma (FVPTC) presents with biological and morphological features similar to papillary thyroid carcinoma. Pre-operative diagnosis of FVPTC and its clinical course is important in identifying appropriate surgical procedures.

METHODS

This study enrolled 85 patients, 68 females (mean age 41.4+/-13.7 years) and 17 males (mean age 50.1+/-12.3 years) with papillary thyroid carcinomas diagnosed as FVPTC. From the patient database at Chang Gung Medical Center (CGMC), 170 pure papillary thyroid carcinoma cases and 85 with minimally invasive follicular thyroid carcinomas of gender- and age-matched patients were randomly selected as control groups. All patients were categorized into high- and low-risk groups according to AMES criteria.

RESULTS

Of the three groups, 7.1% (follicular), 11.8% (FVPTC) and 34.1% (pure papillary thyroid carcinoma) of patients presented with lymph node or soft tissue invasion (P=0.0001). Additionally, 29.4, 11.8 and 2.4% of patients with follicular carcinoma, FVPTC and pure papillary thyroid carcinoma, respectively, presented with distant metastases at the time of diagnosis. Of the 85 FVPTC cases, 75 underwent pre-operative fine needle aspiration cytology (FNAC) examination at CGMC. Only 11 cases were diagnosed pre-operatively with papillary thyroid carcinomas. Kaplan-Meier survival curves for these three groups demonstrated that follicular thyroid carcinoma had a prognosis worse than both papillary thyroid carcinomas.

CONCLUSIONS

Most FVPTC cases were diagnosed as follicular neoplasm via pre-operative FNAC. In this study, FVPTC patients had a high ratio of distant metastases, few lymph node metastases and soft tissue invasion. Aggressive treatment was indicated for the high-risk FVPTC patients.

Role of Fine-needle Aspiration Biopsy and Frozen Section in the Management of Papillary Thyroid Carcinoma Subtypes

Since fine-needle aspiration biopsy (FNAB) was introduced, the value of frozen section (FS) has been questioned. This study compares FNAB and FS sensitivities among the usual form of papillary thyroid cancer (uPTC) and variants of PTC such as tall cell (tcPTC), follicular (fPTC), and Hurthle cell (HcPTC). A total of 257 patients who underwent preoperative FNAB, intraoperative FS, and thyroidectomy for PTC were, randomly selected from a database of a university teaching hospital in Toronto. There were 218 females (84.8%) and 39 males (15.2%), from 19 to 89 years of age (mean of 44 years), having uPTC (n = 212), fPTC (n = 24), HcPTC (n = 14), and tcPTC (n = 7). Data were analyzed using chi2 test. Sensitivities were calculated by division of true positives and by the sum of true positives and false negatives. True positives had to reflect a conclusive diagnosis of cancer. The FNAB sensitivities were uPTC (39.2%), fPTC (25%), HcPTC (42.9%), tcPTC (85.7%), similar to FS sensitivities (p = 0.497) for uPTC (44.3%), fPTC (16.7%), HcPTC (42.9%), and tcPTC (71.4%). Use of FS following FNAB increased sensitivities for uPTC to 56.1%, fPTC to 29.2%, and tcPTC to 100%. In addition, FS did not increase FNAB sensitivity in HcPTC. Combination FNAB plus FS failed in 43.9% of uPTC, 70.8% of fPTC, and 57.1% of HcPTC. We concluded that FNAB and FS sensitivity vary with PTC subtype and are still necessary for selection and treatment. The recognition of morphologic subtypes of PTC from the FNAB could optimize the selection of patients for intraoperative FS, enhance the preoperative assessment of prognosis, facilitate the surgical planning, and simplify the preparation of postoperative adjuvant therapy.

Follicular variant of papillary thyroid carcinoma - a cytological study

The cytological diagnosis of classical papillary carcinoma is easily established based on the characteristic architectural and nuclear features. However, the follicular variant of papillary thyroid carcinoma(FVPTC) poses a diagnostic challenge. In this study we analysed the cytological features of 14 histopathologically proven cases of FVPTC. We inferred that a combination of architectural features such as follicles and syncytial clusters and nuclear features, viz grooves, pseudoinclusions and enlarged nuclei with fine chromatin, were helpful in establishing the diagnosis. It is hence suggested that based on the combination of the aforesaid features a diagnosis of FVPTC be offered whenever it is possible. This helps in patient management, obviating the need for a second surgical intervention.

[Diagnostic relevance of multinucleated giant cells in papillary thyroid cancer. A cytological and histological study]

Cytological smears of 17 papillary carcinomas (PC) of the thyroid as well as histological slides of 58 PC and 50 follicular adenomas (FA) and 50 follicular carcinomas (FC) were reviewed to assess the presence of intrafollicularly located multinucleated giant cells. In accordance with the data published, such giant cells were found in 70% of PC but in only 8% of FA and FC. The presence of giant cells, which probably represents a foreign body reaction to, in case of PC, physicochemically altered colloid, is a useful additional criteria for the cytological and histological diagnosis of PC.

Fine needle aspiration cytology of follicular variant of papillary carcinoma of thyroid

In this retrospective study, we tried to ascertain the fine needle aspiration cytology (FNAC) features of six histopathologically proven cases of the follicular variant of papillary carcinoma of thyroid (FVPCT). These proven cases were diagnosed from 1998-2000. May-Grunwald-Giemsa and haematoxylin & eosin stained FNAC smears were studied independently by two observers (MP and PD) for detailed cytological features. A comparison of the cytological features was undertaken with those reported in the literature. There were six cases of which only one case was diagnosed as FVPCT while the other five cases were diagnosed as follicular neoplasm (four cases) and neoplasm unclassifiable (one case) on FNAC smears. All these cases showed abundant cellularity with a prominent follicular pattern. No papillae were identified in any of the cases. Syncytial clusters (five cases), nuclear grooves (six cases), nuclear inclusions (one case) and chewing gum colloid (three cases) were noted in variable proportions. We suggest that a differential diagnosis of FVPCT should be considered if the cytology smears show abundant cellularity, syncytial clusters and follicular arrangement along with thick colloid.

Thyroid cytology and the risk of malignancy in thyroid nodules: importance of nuclear atypia in indeterminate specimens

Fine needle aspiration (FNA) cytology is the best test for malignancy in thyroid nodules. However, cytologic interpretation of FNA specimens is often difficult, especially in the presence of indeterminate microfollicular cytologic patterns, which are thought to suggest follicular neoplasm (adenoma or carcinoma). To assess the risk of malignancy associated with specific cytologic patterns, we correlated preoperative FNA cytologic patterns (n = 484 reports including repeat aspirations) with final histological diagnoses for 368 surgical thyroid specimens obtained during the period 1994-1998. The overall prevalence of malignancy in the surgical specimens was 31% (113 cancers, including 96 papillary and 9 follicular carcinomas). For nodules with benign FNA cytologic diagnoses of nodular goiter and chronic thyroiditis there was a low risk of malignancy (6/99, or 6.1%). Nodules with indeterminate cytologic patterns in the absence of nuclear atypia (i.e., microfollicles without nuclear atypia) had a similarly low malignancy risk (3/46, or 6.5%). In contrast, 31/52 nodules with cytologic nuclear atypia consistent with follicular neoplasm were malignant (60%), including specimens with or without microfollicular cytology. Nodules with frankly malignant cytologic patterns were almost invariably cancer (54/55), and cytologic diagnoses of papillary carcinoma were confirmed at surgery in all 49 cases. These results indicate that indeterminate microfollicular cytologic patterns in the absence of nuclear atypia are associated with a low risk of malignancy, at least in this series. This finding suggests that many nodules with such microfollicular cytology might be managed conservatively with observation. In contrast, cytologic nuclear atypia consistent with a follicular neoplasm confers a high risk of cancer. In addition, frankly malignant cytologic diagnoses, especially papillary carcinoma, are highly reliable, and thus may be used as a guide for planning surgery appropriate for thyroid cancer.

[Immunodetection of thyroid peroxidase in the diagnosis of follicular variants of thyroid papillary cancer]

STUDY AIM

The aim of this retrospective study was to assess the role of thyroid peroxidase immunodetection in the cytological diagnosis of follicular variants of thyroid papillary cancer (FVTPC) which are difficult to identify by standard cytology.

PATIENTS AND METHODS

Between 1991 and 1998, 3,505 thyroid fine needle aspiration biopsies were performed by thyroid peroxidase immunocytochemistry and 1,576 patients were operated on. Out of a total of 227 thyroid papillary cancers (TPC), 42 (18.5%) were diagnosed as FVTPC. The results of standard cytology and thyroid peroxidase immunodetection were compared with the histological findings.

RESULTS

The rate of false negatives for TPC in standard cytology was 11% (25/227 cases), with 40% of these false negatives being FVTPC; ten out of 42 (23.8%) cases of FVTPC were not identified by standard cytology. However, cytology with thyroid peroxidase immunodetection diagnosed 224 out of the 227 TPC (99%), and all the FVTPC were correctly identified (100%).

CONCLUSION

FVTCP are the most frequent source of false negatives in standard cytology. Thyroid peroxidase immunodetection allows most of these errors to be avoided, and correctly identifies 99% of TPC including FVTPC.

Follicular variant of papillary carcinoma: the diagnostic limitations of preoperative fine-needle aspiration and intraoperative frozen section evaluation

OBJECTIVE

Fine-needle aspiration (FNA) and frozen section (FS) have been widely reported in the literature as having high sensitivity in the diagnosis of papillary carcinoma. With the increased recognition of the follicular variant of papillary thyroid carcinoma (FVPTC), several reports have pointed out the difficulty in diagnosing this variant of papillary carcinoma owing to its overlapping cytomorphological features with benign and malignant follicular lesions. We undertook this study to determine the sensitivity of FNA and FS in the diagnosis of FVPTC.

METHODS

Retrospective review of patients who underwent thyroidectomy from June 1994 to June 1999. Of the 63 patients found with a final pathological diagnosis of papillary thyroid carcinoma, only 47 had an adequate FNA and FS and were included in the study. These patients were divided into two groups, the usual type (n = 23) and the follicular variant (n = 24) of papillary carcinoma. Sensitivities of FNA and FS for these two groups of papillary carcinoma were then determined.

RESULTS

The sensitivity of the FNA was 25% and of the FS was 29% for the follicular variant of papillary thyroid carcinoma. This is in contrast to the sensitivity of FNA and FS for the usual papillary carcinoma, which were 74% and 87%, respectively.

CONCLUSION

FNA and FS have low sensitivity in the diagnosis of the FVPTC. High degree of suspicion may increase the accuracy in the diagnosis of this variant of papillary carcinoma before or during surgery. However, the thyroid surgeon needs to realize that, like follicular carcinoma, FVPTC is often diagnosed only on final pathological examination.