Cytological and molecular diagnosis of solid variant of papillary thyroid carcinoma: a case report

Solid variant of papillary thyroid carcinoma: an under-recognized entity

Solid variant of papillary thyroid carcinoma (SVPTC) is a rare morphological variant of papillary thyroid carcinoma (PTC). SVPTC is histologically characterized by predominant solid, trabecular and insular nests of tumor cells while cytological features of PTC such as nuclear grooves and nuclear inclusions are preserved. In fine needle aspiration cytology smears, tumor cells of SVPTC may be presented in cohesive, syncytial or trabecular clusters accompanied by some discohesiveness in the absence of necrosis. Although SVPTC and poorly differentiated thyroid carcinoma (PDTC) share similar histological findings of solid nests, SVPTC can be differentiated from PDTC in the lack of tumor necrosis, severe nuclear atypia, and a higher mitotic index. Immunohistochemical expression of CK19 and HBME-1, common markers of PTC, is decreased in solid nests of SVPTC. In pediatric patients exposed to radiation after the Chernobyl nuclear accident, there was a higher prevalence of SVPTC with RET/PTC3 type rearrangement. BRAF mutations are also reported in a small number of adult patients with SVPTC without any prior radiation exposure. Patients with SVPTC may have a slightly higher incidence of metastasis and recurrence of the tumor compared to conventional PTC, although overall survival rate is comparable. In this article, the current knowledge of SVPTC will be reviewed and discussed with an emphasis on the histopathological feature.

Solid papillary thyroid carcinoma with Hashimoto's thyroiditis: description of a further case with challenging cytological features

Solid papillary thyroid carcinoma (SV-PTC) is a rare variant which is mainly observed in young patients with a history of exposure to ionising radiations. Neoplasms belonging to such category generally carry RET-PTC (REarranged during Transfection- Papillary Thyroid Carcinoma) fusions and seem to have a slightly worse prognosis with respect to classical and follicular variants of papillary thyroid carcinoma (PTC), though consistent prognostic and survival data are scarce. SV-PTC should be differentiated from trabecular-insular poorly differentiated thyroid carcinomas, which occur in a different age group and carry a dismal prognosis. These latter tumours do not show the typical nuclear features of PTC and show tumour necrosis with an high mitotic activity. In this report a further case of SV-PTC is described which was associated to Hashimoto's thyroiditis, a finding never described in the cytological literature up to now for SV-PTC; this association created further differential diagnostic problems. The neoplasm displayed RET-PTC1 fusion.

Cytopathology of Solid Variant of Papillary Thyroid Carcinoma: Differential Diagnoses with other Thyroid Tumors

OBJECTIVES

Solid variant of papillary thyroid carcinoma (SVPTC) is rare, differing from classical PTC (cPTC) in architecture and outcome. We evaluated the cytomorphology of SVPTC cases to assess the feasibility of a preoperative diagnosis.

STUDY DESIGN

SVPTC cases were evaluated for architecture, nuclear features, and Bethesda category and were compared with noninvasive follicular thyroid neoplasm with papillary-like nuclear features/follicular variant of PTC (NIFTP/FVPTC), cPTC, and poorly differentiated thyroid carcinoma (PDTC).

RESULTS

Nine SVPTCs, 29 NIFTP/FVPTCs, 12 cPTCs, and 4 PDTCs were included. The predominant architecture in most SVPTCs was solid fragment, which is helpful in differentiating them from NIFTP/FVPTC (p < 0.001) and cPTC (p = 0.006) but not from PDTC. The presence of microfollicles led to misinterpretation as NIFTP/FVPTC/follicular neoplasm in 4 patients. All but 1 SVPTC showed diffuse nuclear features. Intranuclear pseudoinclusions (INIs) were seen in 67% of SVPTCs as compared to 83% of cPTCs, 14% of NIFTP/FVPTCs (p = 0.005), and none of PDTCs. SVPTC cases were commonly (78%) categorized as intermediate/suspicious.

CONCLUSIONS

The presence of solid fragments and lack of true papillae are helpful in differentiating SVPTC from cPTC. Solid fragments, trabeculae, the extent of nuclear features, and INIs should be looked for in cases with prominent microfollicles for distinguishing SVPTC from NIFTP/FVPTC. None of the features were helpful in differentiating SVPTC from PDTC.

Fine needle aspiration cytology of the papillary thyroid carcinoma with a solid component: A cytological and clinical correlation

BACKGROUND

Solid variant of papillary thyroid carcinoma is a rare subtype of papillary thyroid carcinoma (PTC) containing a solid component (SC), and thus its cytological and clinicopathological features remain elusive. We examined fine needle aspiration (FNA) cytological features of PTC with variable degrees of SC (20-80% of the tumor)(PTCSC) in comparison to well-differentiated PTC (WPTC).

METHODS

Twenty-six cases of PTCSC were histologically stratified into major-SC (SC >50% of the tumor) and minor-SC (<49%) groups. Pre-operative FNA smears were compared between major-SC (n = 11) and minor-SC (n = 15) groups, and between PTCSC and WPTC (n = 39) groups.

RESULTS

In FNA smears of PTCSC, the presence of cohesive solid nests, trabecular patterns, overlapping, enlarged nuclei, pleomorphism, and distinct nucleolus, and the absence of colloid and psammoma bodies were noted more often than in WPTC, while classical cytological features of PTC, such as nuclear grooves and/or pseudo-nuclear inclusions, were preserved. There was no significant difference in FNA findings between the major-SC and minor-SC groups. The presence of either solid nests or trabecular patterns, and overlapping in FNA smears of PTCSC was associated with a higher recurrence rate of the tumor (P = 0.007 and P < 0.001, respectively).

CONCLUSION

PTCSC may pre-operatively be identified by detecting its characteristic cytological features in FNA smears, regardless of the proportion of SC within the tumor. Because clinical outcomes of PTCSC remain undetermined, it is imperative to postulate PTCSC as a differential diagnosis, even when classical nuclear features of PTC are present. Diagn. Cytopathol. 2017;45:391-398. © 2017 Wiley Periodicals, Inc.

Cytological features of solid variants of papillary thyroid carcinoma: a fine needle aspiration cytology study of 18 cases

OBJECTIVE

Solid variants of papillary thyroid carcinoma (SV-PTC) are rare, and there have been few reports describing the cytological findings of such variants.

METHODS

The cytological features of cellular specimens aspirated from 18 histologically confirmed SV-PTC cases were evaluated, retrospectively.

RESULTS

Solid and small papillary clusters were observed in 14 (77.8%) and 13 (72.2%) cases, respectively. The incidences of large papillary clusters (11.1%) and sheet-like arrangements (11.1%) were low. Nuclear features were consistent with conventional PTC. The background was clean, and there were no colloid materials, foamy histiocytes, multinucleated giant cells, psammoma bodies, or necrotic materials.

CONCLUSIONS

Solid clusters and small papillary clusters in conjunction with a clean background are diagnostic clues that indicate SV-PTC cytologically. It is thought that small papillary clusters reflect the micropapillary growth pattern seen within the lumen of middle-sized follicular structures. The presence of nuclear findings typical of conventional PTC and the absence of mitotic figures and necrotic materials are important for distinguishing SV-PTC from poorly differentiated carcinoma.

A 3-bp Deletion VK600-1E in the BRAF Gene Detected in a Young Woman with Papillary Thyroid Carcinoma

Papillary thyroid cancer (PTC) derived from follicular cells is a frequent thyroid tumor. The incidence of this type of malignancy is still growing worldwide. Several major genetic causes are recognized to cause PTC-mutations in the BRAF and RAS genes or rearrangements with the RET proto-oncogene. The most common genetic change found in PTC is a V600E mutation in the BRAF gene presented in 36-69 % of all PTC cases. For routine purposes, several methods were developed to selectively detect only this mutation. However, these methods miss other mutations in the BRAF gene located elsewhere. We focused on the analysis of the exon 15 of the BRAF gene by next-generation sequencing. Here we report a three nucleotide deletion VK600-1E in one patient and present this finding in the context of 13 previously described PTC cases with this deletion. Our patient is the second youngest one among the reported cases. Clinical features of PTC patients with VK600-1E are summarized. For the future, it is important to evaluate genotype-phenotype characteristics of patients with rare BRAF mutations and to follow up them for years.

Fine-needle aspiration cytology of the solid variant of papillary thyroid carcinoma: a study of 13 cases with clinical, histologic, and ultrasound correlations

BACKGROUND

The solid variant of papillary thyroid carcinoma (SVPTC) comprises approximately 3% of thyroid cancers, and there are conflicting reports about its behavior in the literature. The cytology of SVPTC is limited to 3 single case reports, a review article, and a monograph. We present the first cytologic study of SVPTC.

METHODS

Fine-needle aspiration smears obtained with ultrasound guidance from 13 patients with histologically pure SVPTC were reviewed, and the cytologic features recorded. Ultrasound images were retrieved from radiology and were correlated with low-power histology images. Intratumor vascularity on Doppler imaging was correlated with cellularity in cytology samples.

RESULTS

Three cytomorphologic patterns of SVPTC were identified: cohesive, syncytial-type tissue fragments; microfollicles/trabeculae; and dyshesive single cells. All 3 SVPTCs in the first group were encapsulated without invasion. Two of 6 SVPTCs in the second group had a single lymph node metastasis; 4 were encapsulated, and 2 had pushing borders. Ultrasound images in the first and second SVPTC groups were similar, with the majority revealing a well defined, solid nodule with minimal intranodular vascularity. All 4 SVPTCs in the third group had infiltrative borders; and, with the exception of one 0.8-cm tumor, all had multiple lymph node metastases. Ultrasound in the third group revealed irregular borders. RET/PTC1 and RET/PTC3 mutations were found in 2 cases of the third group.

CONCLUSIONS

SVPTCs are heterogeneous tumors. The cohesive, syncytial tissue-fragment pattern can be recognized as SVPTC in smears and is associated with encapsulation and indolent behavior. The microfollicular/trabecular pattern is indistinguishable from that of the follicular variant of papillary thyroid carcinoma and has intermediate behavior. The dyshesive single-cell pattern correlates with infiltrative tumor growth and may not be unique to SVPTC.

Aggressive variants of follicular cell-derived thyroid carcinomas: a cytopathologist's perspective

Follicular cell-derived carcinomas of the thyroid gland comprise a heterogeneous group of malignant neoplasms of the thyroid gland with varied histologic appearance and molecular profiles. In most patients, these tumors represent relatively indolent neoplasms; however, certain subtypes/variants behave in an aggressive manner, and the recognition of this subset of tumors is essential because of their variable response to therapy and significant morbidity and mortality. Fine-needle aspiration is considered an essential tool for the diagnosis of suspicious thyroid nodules. In this review, the authors discuss the clinical, histologic, and molecular findings and the prognostic implications of aggressive thyroid neoplasms with emphasis on the characteristic cytomorphologic features on fine-needle aspiration smears.

Utility of molecular tests in cytopathology

With the popularity of interventional radiology, diagnostic material obtained can be limited requiring critical decisions on making the best use of it. Molecular testing using nanogram amounts of tissue can add useful diagnostic information by improving sensitivity and/or specificity of the diagnosis. This review examines the use of molecular tests in cervical cytology, "indeterminate" thyroid cytology specimens, pancreatic cyst fluid, urinary tract and pulmonary adenocarcinoma cytologic material. Molecular human papillomavirus (HPV) testing combined with cervical cytology increases sensitivity of detection of high grade lesions. In cytologically negative cases, the HPV negative predictive value endorses longer screening intervals. With the high prevalence of benign thyroid nodules, cytology plays a vital role in screening. However, 10-40% of the specimens obtained are cytologically indeterminate. Molecular analysis of these specimens can predict the malignant risk in these cases. Increased detection of pancreatic cysts has necessitated accurate pre-operative diagnosis delineating non-mucinous from mucinous cysts, which have a potential for progression to adenocarcinoma. Multimodal diagnosis of pancreatic cysts and molecular analysis help to clarify neoplastic risk; and in cases of limited fluid, may be the only available diagnostic information. Urothelial carcinoma (UC) of the bladder, a common cancer with frequent recurrences, requires lifelong surveillance. The UroVysion ™ test kit can increase the sensitivity of detection of UC especially in cases of residual/recurrent carcinoma after therapy. Subsets of lung adenocarcinomas are now commonly targeted by therapies based on molecular mutation results of epidermal growth factor receptor, KRAS or echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase re-arrangements. The move toward standardization of reporting of cytology specimens commencing with cervical smears and more recently, thyroid cytology specimens is also changing the practice of cytopathology. Combining the stringent cytology criteria with ancillary molecular testing is expected to yield more discrete and diagnostic categories for research and reporting. The profession is at an exciting point of implementing novel molecular markers to refine diagnostic criteria and create clinically relevant classification systems.

PAX8 is expressed in anaplastic thyroid carcinoma diagnosed by fine-needle aspiration: a study of three cases with histological correlates

OBJECTIVE

It is difficult to diagnose anaplastic thyroid carcinoma (ATC) in a fine-needle aspiration (FNA) sample because, given the loss of morphological and immunophenotypical follicular thyroid features, its cytology resembles that of other undifferentiated neoplasms. Recent studies have shown that immunostaining for paired box gene 8 (PAX8), a transcription factor expressed in normal thyroid, is effective for diagnosing ATCs on histology. The aim of this study was to evaluate whether PAX8 could be used to identify ATCs on cytology also.

DESIGN AND METHODS

We selected three PAX8-immunostained undifferentiated FNA samples previously diagnosed as suspected ATCs, whose cell block had been negative for the expression of TGB and thyroid transcription factor-1. Matched histological samples, available in two cases, were also processed for PAX8 immunohistochemistry.

RESULTS

All three FNA samples were PAX8 positive. Two samples that had an epithelioid pattern showed a diffuse, intense nuclear signal. The third sample, which had a spindle-cell pattern, showed less intense and more patchy staining. Matched histology yielded overlapping results.

CONCLUSIONS

PAX8 immunocytochemistry can help cytopathologists to diagnose ATCs.

Pituitary metastasis of thyroid cancer

Pituitary metastases (PM) from thyroid cancer are rare, but their management can represent a difficult challenge for the endocrinologist. Our aim was to review all reported cases of PM from thyroid cancer. PubMed was consulted and 19 papers reporting 20 cases were found. We moreover discuss two of our own cases, which had come to our attention within a few months of one another. Eleven cases were follicular cancer, eight cases were papillary cancer, two cases were medullary cancer, and one case was an insular cancer. In nine cases, PM was the first sign of the disease. Cranial nerve involvement was the most common sign of its presence, and no neuroradiological imaging could lead to a sure diagnosis of PM. Neurosurgical intervention was performed in almost all cases, and post-surgical treatment comprised radioiodine, external beam radiotherapy, and radiosurgery. Prognosis was poor for larger metastases, cranial nerve palsy disappeared in only one case, and in only one case of intrasellar metastasis was the disease cured. PM from thyroid cancer are rare, but are burdened by a poor prognosis. An early diagnosis appears important, and a comprehensive strategy for treatment (neurosurgery, radioiodine, external radiotherapy, and radiosurgery) appears advisable.

Cyclin D1 and D3 overexpression predicts malignant behavior in thyroid fine-needle aspirates suspicious for Hurthle cell neoplasms

BACKGROUND

Thyroid fine-needle aspiration (FNA) samples that feature a follicular-patterned, monotonous Hurthle (oncocytic) cell population cannot be diagnosed reliably. The authors of this report recently identified cyclin D3 overexpression on histologic sections of Hurthle cell carcinoma. In this study, they assessed the diagnostic value of cyclin D3 immunohistochemistry added to routine cytology.

METHODS

Fifty-one FNA samples that were suspicious for Hurtle cell neoplasia and that had histologic follow-up (19 malignant cases) were examined. Cyclin D3 expression levels were evaluated in cell block preparations and were compared with levels of the closely related cyclin D1 protein.

RESULTS

Greater than 25% positive cells were used as the cutoff point, as suggested by previous studies. Cyclin D1 and cyclin D3 were highly specific (100% for both) and fairly accurate (75% and 92%, respectively) in distinguishing between benign and malignant oncocytic lesions; the positive predictive value (PPV) for each was 100%. However, both cyclins D1 and D3 had low sensitivity (32% and 79%, respectively) and low negative predictive value (NPV) (71% and 89%, respectively). In contrast, by adopting balanced receiver operating characteristic-derived positive cutoff values, cyclin D1 (>or=6.5%) and cyclin D3 (>or=7.5%) were found to be highly sensitive (100% for both) and accurate (90% and 94%, respectively); and the NPV was 100% for both. In contrast, cyclins D1 and D3 had low specificity (84% and 91%, respectively) and a low PPV (79% and 86%, respectively); however, these values improved in samples that were positive for both cyclins (sensitivity, 100%; specificity, 94%; PPV, 90%; NPV, 100%; and accuracy, 96%).

CONCLUSIONS

Cyclin D3 increased the suspicion of malignancy in indeterminate oncocytic lesions; its diagnostic performance depended on the cutoff point used and was enhanced further when combined with cyclin D1.