Identification of metastatic papillary thyroid carcinoma in FNA specimens using thyroid peroxidase immunohistochemistry

Canine follicular cell and medullary thyroid carcinomas: Immunohistochemical characterization

Research on modulation of iodine uptake by thyroid cells could help improve radioiodine treatment of dogs with thyroid tumors. The aim of this study was to characterize the immunohistochemical expression of thyroid transcription factor-1 (TTF-1), thyroglobulin, thyrotropin receptor (TSHR), sodium iodide symporter (NIS), pendrin, thyroid peroxidase (TPO), vimentin, and Ki-67 in follicular cell thyroid carcinomas (FTCs) and medullary thyroid carcinomas (MTCs), and to compare protein expression between FTC causing hyperthyroidism and FTC of euthyroid dogs. Immunohistochemistry was performed in 25 FTCs (9 follicular, 8 follicular-compact, and 8 compact) and 8 MTCs. FTCs and MTCs were positive for TTF-1, and expression was higher in FTCs of euthyroid dogs compared with FTCs of hyperthyroid dogs (P= .041). Immunolabeling for thyroglobulin was higher in follicular and follicular-compact FTCs compared with compact FTCs (P = .001), while vimentin expression was higher in follicular-compact FTCs compared with follicular FTCs (P = .011). The expression of TSHR, NIS, pendrin, and TPO was not significantly different among the different subtypes of FTCs or between FTCs causing hyperthyroidism and FTCs in euthyroid dogs. TSHR, NIS, pendrin, and TPO were also expressed in MTCs. Ki-67 labeling index was comparable between FTCs and MTCs, and between FTCs causing hyperthyroidism and FTCs in euthyroid dogs. Proteins of iodine transport were also expressed in canine MTCs, which could have implications for diagnosis and treatment. The different expression of thyroglobulin and vimentin between FTC histological subtypes could reflect variations in tumor differentiation.

Diagnostic utility of anti-thyroid peroxidase immunohistochemistry in the identification of papillary thyroid carcinoma

The routine histomorphological assessment of follicular thyroid neoplasms has been subject to interobserver or intraobserver variability among histopathologists. Anti-thyroid peroxidase (anti-TPO) has emerged as a useful immunohistochemical (IHC) marker, with its expression lost in papillary thyroid carcinoma (PTC). Our study aims to determine the diagnostic accuracy of anti-TPO IHC expression in the identifying PTC and its variants, particularly the Follicular variant of papillary thyroid carcinoma (FVPTC), with H&E assessment as the gold standard. Anti-TPO IHC (DAKO-MoAb47) was performed on 110 cases, including 76 malignant tumors (classic PTC, FVPTC, follicular carcinoma (FC), and oncocytic carcinoma (OC)) and 34 benign tumors (non-invasive follicular tumor with papillary-like nuclear features (NIFTP) and follicular adenoma (FA)). The loss of expression in more than or equal to 51 % of thyrocytes was considered suggestive of a PTC profile. The sensitivity of the loss of anti-TPO expression for identifying PTC among all carcinomas was 61.7 %, specificity was 75 %, positive predictive value was 90.2 %, negative predictive value was 34.2 %, and accuracy was 64.4 %. The loss of anti-TPO IHC expression combined with routine H&E assessment, supports the identification of PTC and its variants.

Carcinoma of Unknown Primary Origin: Application of Immunohistochemistry With Emphasis to Different Cytokeratin 7 and 20 Staining Patterns

BACKGROUND

Although the primary origin of some carcinomas may be obscure to clinicians, its identification is crucial as it affects prognosis and treatment (especially novel targeted therapies). Immunohistochemistry (IHC) may be helpful in identifying the primary origin of carcinomas. This retrospective survey aimed to evaluate the frequency and accuracy of each IHC marker used to determine the origin of carcinomas.

METHODS

The review of pathology department archives revealed 307 cases of cancer of unknown primary origin (CUP) between 2015 and 2020, which were accessible in the department archives. Demographic information, site of biopsy, clinical and pathologic diagnoses, and IHC results of the patients were collected.

RESULTS

The patients included 157 (51.15%) men and 150 (48.85%) women. The age of the patients ranged from 14 to 92 years, including 106 (34.5%) expired cases. In 27% of cases, the primary origin of carcinoma remained unknown. The agreement between pathologic and clinical diagnoses was 59%. The most common pattern of cytokeratin (CK) expression in CUP was CK7+/CK20- (55.3%), followed by CK7-/CK20- (19%), CK7+/CK20+ (15%), and CK7-/CK20+ (10.7%), respectively.

CONCLUSION

The IHC analysis may improve the diagnosis of CUPs. However, the origin of some cases remains unknown despite an IHC analysis, thereby necessitating the use of more diagnostic procedures or gene expression studies for reaching a definitive diagnosis.

Cytopathology of the distant metastasis of papillary carcinoma of thyroid

AIMS

To describe the cytomorphological features at distant metastatic sites apart from lymph nodes in papillary thyroid carcinoma (PTC).

MATERIALS AND METHODS

A total of eight cytology cases from seven patients reported as metastatic papillary carcinoma of thyroid were reviewed including available clinical and radiological details. The details clinical and cytological features were studied.

RESULTS

There were a total of five males and two female patients. Two of these patients presented with lung nodules, two patients had bony lesion and lesion in kidney respectively and one patient had both bony and soft tissue lesions. Pleural fluid and bronchoalveolar lavage were received from remaining two patients. Cytology smears revealed papillary clusters and sheets of tumor cells, having round to oval nuclei with pale powdery chromatin, inconspicuous nucleoli and scant to moderate amount of cytoplasm. Nuclear features such as longitudinal nuclear grooves, intranuclear cytoplasmic inclusions were seen in all but one case. Nuclear enlargement and overlapping were variably present.

CONCLUSIONS

The diagnosis of metastatic PTC at uncommon locations is difficult. Since many of these locations are amenable to fine needle aspiration or exfoliative cytology evaluation, clinical awareness, and identification of classic cytomorphologic features can offer quick and accurate diagnoses. In cases with occult or unknown PTC presenting with metastases, cytomorphology may help in the prompt suggestion of detecting primary tumor in the thyroid.