Thyroid nodules are a common clinical problem, and fine-needle aspiration biopsy (FNAB) is widely used for its evaluation. Only 5% are malignant, being papillary carcinoma (PC) the most frequent neoplasia. Approximately 20% are classified as indeterminate or suspicious for malignancy. Gene-expression pattern may be useful for diagnosing PC in difficult or ambiguous cases. In our prior study, we were able to apply RT-PCR method in a series of routinely performed FNAB of thyroid nodules using individual, residual samples. In this study, a total of 70 thyroid samples were evaluated for the expression of MPPED2, H/HBA2, MET, FN1, GALE, and QPCT genes, including 24 cases of frozen thyroid tissue, 12 nodular hyperplasia and 12 PC, and the 46 consecutive thyroid FNAB samples, previously analyzed (3 positive, 10 indeterminate and 32 negative for malignancy, and 1 insufficient). FN1, GALE, MET, and QPCT mRNA expression were significantly different in benign and malignant samples, with similar pattern of overexpression in aspirates compared to frozen tissue. H/HBA2 and MPPED2 expression varied. Histological correlation was possible in five indeterminate cases, revealing one PC and four benign lesions. In conclusion, FN1, GALE, MET, and QPCT were significantly overexpressed in thyroid PC. RT-PCR method could be applied to routine FNAB, showing a similar pattern of overexpression. Despite the small number of cases evaluated, our results suggest that molecular analysis may be of assistance in patients with indeterminate/suspicious cytology, adding elements for preoperative diagnosis and better management of these patients.

Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal neoplasia and currently well recognized as a distinct entity with characteristic morphological, immunohistochemical and molecular findings. We report a case of PEComa arising in the antrum of a 71-year-old female with melena. The tumor, located predominantly in the submucosa as a well delimited nodule, measured 3.0 cm in diameter and was completely resected, with no evidence of the disease elsewhere. Histologically, it was composed predominantly of eosinophilic epithelioid cells arranged in small nests commonly related to variably sized vessels, with abundant extracellular material, moderate nuclear variation and discrete mitotic activity. No necrosis, angiolymphatic invasion or perineural infiltration was seen. Tumor cells were uniformly positive for vimentin, smooth muscle actin, desmin and melan A. Although unusual, PEComa should be considered in the differential diagnosis of gastric neoplasia with characteristic epithelioid and oncocytic features and prominent vasculature.

Pilomatrixoma (calcifying epithelioma of Malherbe) is an uncommon benign skin appendageal tumor that differentiates toward hair matrix cells. It is misdiagnosed in up to 75% of cases by nondermatologists. Although the histopathological findings are well recognized and characteristic, diagnosis by fine-needle aspiration biopsy may be quite challenging. Several reports have emphasized the challenges in cytodiagnosis of pilomatrixoma, leading to a false-positive diagnosis. The lesions may show avidity for fludeoxyglucose on positron emission tomography/computed tomography scan, raising concern of a possible malignant neoplasm. CTNNB1 mutations have been reported in a high percentage of pilomatrixomas. Expression of β-catenin, the protein encoded by CTNNB1, is also frequently observed. To determine if routine cytological specimens can be successfully used to perform additional investigation and support or confirm the diagnosis in three cases of pilomatrixoma, we performed molecular analysis and immunohistochemistry to search for CTNNB1 mutation and β-catenin, respectively. β-Catenin positivity by immunohistochemistry was observed in basaloid cells in all three cases. Exon 3 mutations in CTNNB1 were detected in all cases. In addition, we detected a fibroblast growth factor receptor 2 (FGFR2) mutation in one of the cases. We reviewed the literature and present the clinical and morphological characteristics that must be considered along with other findings to accurately achieve the correct diagnosis, in correlation with the results of the ancillary technique. In conclusion, routine cytological specimens can be successfully used to perform additional investigations and support cytodiagnosis in difficult cases.

Thyroid nodules are frequent in clinical practice and fine-needle aspiration biopsy (FNAB) is widely used for its evaluation, but approximately 20% of the cases are diagnosed as indeterminate for malignancy. Aspirates from thyroid nodules can be used for ancillary methods, but molecular techniques are not routinely applied to these specimens. Forty-six consecutive, routinely performed, FNAB of thyroid nodules were evaluated for the feasibility of applying RT-PCR method. RNA was extracted from 1 of 3 fresh residual samples and analyzed to determine its pureness, integrity, and concentration. Cellularity was adequate in all 46, except one, specimens analyzed, scored as 0, 1+, 2+, 3+, and 4+ in 1, 10, 14, 9, and 8 cases, respectively. Thirty-three nodules measured less than 1.5 cm. Cytological diagnosis was positive for malignancy in 3 cases, indeterminate for malignancy in 3, most probably benign follicular lesion in 7, negative for malignancy in 32, and suggestive of benign follicular lesion in 1. Good quality RNA was successfully isolated in 45/46 (97.8%) samples, with an average RNA concentration of 14 ng/microl and detection of B2M mRNA in 97.7% (44/45). There was no significant correlation between RNA concentration and nodule size or specimen cellularity. In conclusion, molecular analysis using individual, residual samples of thyroid nodules aspirates is feasible and could be employed for molecular preoperative studies in the future, adding elements for final cytological diagnosis of indeterminate cases, without altering the routine procedure.