Parathyroid tumors (PTs) are sometimes difficult to diagnose because they are small and have a low-velocity blood flow, which can be missed by current imaging modalities. PTs consist of parathyroid adenoma (PA), parathyroid cyst, and parathyroid carcinoma (PC). Detective flow imaging (DFI) is a new imaging technology that displays a low-velocity blood flow. Herein, we report two cases in which DFI was useful for the diagnosis of PTs. One case consisted of a PA and a parathyroid cyst in close proximity, and the other was a PC. To the best of our knowledge, this is the first report to demonstrate the usefulness of DFI in the diagnosis of PTs.

Background: Adenoid cystic carcinoma of the trachea (ACCT) is a rare cancer; ACCT with thyroid invasion is particularly rare. We first suspected anaplastic thyroid carcinoma (ATC) but diagnosed ACC after performing fine needle aspiration cytology (FNAC). A tracheal origin was confirmed after operation. Case Description: We report the case of a 77-year-old female presenting to our hospital with acute inspiratory dyspnea requiring emergency tracheotomy. Physical examination revealed a right anterior neck swelling with a hard and unmovable mass. Computed tomography (CT) and ultrasonography (US) showed tumor extension to the right thyroid lobe, and between the first and third tracheal rings, which caused severe stenosis of the lumen. Next, we performed FNAC. Clinical findings were highly suspicious for ACCT with thyroid invasion. Thirty-five days after the first visit to our department, the patient underwent total laryngectomy, cervical esophagectomy, and thyroidectomy with bilateral selective neck dissections at another hospital. The tumor was located in the right posterior wall of the trachea, with extension into the right thyroid gland. Pathological examination showed an infiltrative carcinomatous proliferation with tubular and cribriform patterns. The tumor was classified as pT4N1. A definite diagnosis was made after histopathological analyis of the surgical specimen confirmed ACCT. The tumor was found to be positive for FABP7, a putative prognostic marker of ACC, and metastasized to the lungs 3 years after the surgery. Conclusions: ACCT with thyroid invasion is an extremely rare malignant neoplasm. FNAC was useful for differentiating ACCT from other diagnoses and enabled appropriate surgical treatment.

Fine-needle aspiration biopsy (FNAB), an important diagnostic tool given its simplicity, safety, and cost-effectiveness, is fast becoming a popular procedure in the diagnosis of thyroid diseases. Generally, cells isolated from biopsies are transferred directly to microscope slides to prepare smears for cytopathological examination; however, the technical difficulties of this procedure often cause poor reproducibility, which limits the accuracy of diagnostic results. Liquid-based cytology (LBC), in which isolated cells are collected in a fixative solution, is advantageous in that it facilitates the preparation of homogenous cytological specimens. However, LBC has not been applied to molecular diagnoses, such as RNA expression-based diagnosis, mainly because of difficulties in cell recovery and RNA isolation. This study was aimed to improve RNA extraction from papillary cancer-derived K1 cells and thyroid FNAB specimens suspended in LBC solutions. K1 cells suspended in CytoRich-Red and CytoRich-Blue, fixatives for LBC, were efficiently recovered by trapping to glass-fiber filters. Importantly, subsequent Proteinase K treatment was essential for efficient RNA extraction from the fixed cells. This finding was also applicable to RNA extraction from CytoRich-Red-fixed thyroid FNAB specimens processed in the same way. Consistently, U6 small nuclear RNA was detected in these RNA samples by reverse transcription-polymerase chain reaction.

Background: Detective flow imaging (DFI) is a new imaging technology that displays low-velocity blood flow, which is difficult to visualize on conventional color Doppler ultrasonography (CDU). In this study, we compared the usefulness of DFI with that of CDU and methoxy-isobutyl-isonitrile (MIBI) scintigraphy for detecting parathyroid adenoma (PA) in patients with primary hyperparathyroidism (PHPT). Methods: From March 2021 to March 2023, 87 PHPT patients underwent surgery, and 66 had a single PA. We performed preoperative conventional ultrasonography with CDU, MIBI scintigraphy, and DFI for 42 patients (5 males and 37 females; mean age: 61.6 ± 15.4 years). Results: MIBI scintigraphy detected PA in 85.7% (36/42) patients, and both CDU and DFI detected PA in all patients. The rates of vascularity in PA detected by CDU and DFI were 71.4% (30/42) and 85.7% (36/42), respectively. Vascularity was detected by DFI in 6 patients who were negative for vascularity on MIBI scintigraphy. Furthermore, DFI detected blood supply in 6 of the 12 patients with undetectable blood supply on CDU. Fisher's exact test revealed that high or low blood flow, as determined by DFI, was significantly associated with detection of feeding vessels in PA by CDU (P < 0.001). Conclusions: DFI was useful for preoperative detection of PA blood flow.