Thyroid tubercle of Zuckerkandl (TZ) is a nodule arising from the posterolateral thyroid, considered to be a remnant of the ultimobranchial body (UB). Considering that C cells and solid cell nests also arise from the UB, we hypothesized that these would be present in the TZ. We examined the presence of C cells and solid cell nests in the TZ using the histological analyses of 21 patients with grade 2 or 3 TZs following Pelizzo’s grading system. Out of 21 TZs, 19 (90.5%) were located in the right lobe of the thyroid. Microscopically, solid cell nests were found within the TZ in 1 case (4.8%), and within the main thyroid tissues in 3 cases (14.3%). Calcitonin-positive C cells were scattered within the TZ in 1 case (4.8%), and within the main thyroid tissue in 15 cases (71.4%). The distribution of C cells within the main thyroid tissue was denser than that within the TZ. The above-mentioned results indicated the lack of C cells and solid cell nests in the TZ. Although the TZ may have an embryological origin different from that of ordinary thyroid tissue, it is unlikely that the remnants of the UB are involved in the formation of the TZ.
Abstract Background Only one thyroid follicular cell-derived tumor with a purely trabecular growth pattern has previously been described. This report aims to describe the histological, immunohistochemical, and molecular findings of our second case, propose a novel thyroid tumor, and discuss its diagnostic pitfalls. Case presentation A 68-year-old female presented with an encapsulated thyroid tumor composed of thin and long trabeculae. No papillary, follicular, solid, or insular patterns are observed. The tumor cells were elongated or fusiform and arranged perpendicular to the trabecular axis. No nuclear findings of papillary thyroid carcinoma and increased basement membrane material were found. Immunohistochemically, the tumor cells were positive for paired-box gene 8, thyroid transcription factor-1, and negative for thyroglobulin, calcitonin, and chromogranin A. Inter- and intra-trabecular accumulation of type IV collagen-positive materials was not demonstrated. None of PAX8/GLIS1 and PAX8/GLIS3 and mutations in BRAF, HRAS, KRAS, NRAS, TERT promoter, CTNNB1, PTEN, and RET were detected. Conclusions We report our case as a novel disease entity called non-hyalinizing trabecular thyroid adenoma, which has the diagnostic pitfalls of hyalinizing trabecular tumor and medullary thyroid carcinoma.
Double-stranded RNA (dsRNA)-specific adenosine deaminase converts adenosine to inosine in dsRNA. The protein has been purified from calf thymus, and here we describe the cloning of cDNAs encoding both the human and rat proteins as well as a partial bovine clone. The human and rat clones are very similar at the amino acid level except at their N termini and contain three dsRNA binding motifs, a putative nuclear targeting signal, and a possible deaminase motif. Antibodies raised against the protein encoded by the partial bovine clone specifically recognize the calf thymus dsRNA adenosine deaminase. Furthermore, the antibodies can immunodeplete a calf thymus extract of dsRNA adenosine deaminase activity, and the activity can be restored by addition of pure bovine deaminase. Staining of HeLa cells confirms the nuclear localization of the dsRNA-specific adenosine deaminase. In situ hybridization in rat brain slices indicates a widespread distribution of the enzyme in the brain.
The pathogenesis of thyroid lymphoepithelial cysts is controversial, and two hypotheses have been proposed, namely derivation from branchial-derived remnants or from squamous metaplasia of the follicular cells. The aim of this study was to clarify the pathogenesis of thyroid lymphoepithelial cysts. We performed pathological and immunohistochemical examination of 21 thyroid lymphoepithelial cysts, 13 non-neoplastic squamous metaplasia samples without thyroid carcinoma, 13 solid cell nests, and 14 lateral cervical cysts. On ultrasound, half of thyroid lymphoepithelial cysts were interpreted as calcified nodules regardless of no calcification. Thyroid lymphoepithelial cysts and squamous metaplasia tended to be located in the central and lower portions of the thyroid, while solid cell nests were located in the upper and central portions (p < 0.05). In 95.2% of patients with thyroid lymphoepithelial cysts and all patients with squamous metaplasia, lesions were histologically associated with chronic thyroiditis forming lymph follicles. Hashimoto's disease was serologically confirmed in 18 patients with lymphoepithelial cysts (85.7%) and 10 patients with squamous metaplasia (76.9%). Immunohistochemically, lymphoepithelial cysts showed nuclear positivity for PAX8, thyroid transcription factor 1, and p63. One lateral cervical cyst (7.1%) showed positive staining for PAX8, while solid cell nests were PAX8-negative. In three (14.3%) cases of thyroid lymphoepithelial cysts, squamous cells located on the superficial layer were focally and weakly positive for CEA. We concluded that thyroid lymphoepithelial cysts originate from follicular cells and are unrelated to solid cell nests and lateral cervical cysts arising from branchial-derived remnants.
Objective: The simplest way to determine the adequacy of aspirated materials is the on-site gross visual assessment of aspirated materials. However, few studies have examined the gross findings of thyroid aspirates. This study aimed to clarify the diagnostic significance of clay-like material aspirated from thyroid nodules. Material and Methods: We reviewed 69,848 thyroid nodules that underwent aspiration cytology at Kuma Hospital between January 2007 and August 2021. Among them, 355 (0.5%) nodules with aspirated materials described as clay-like materials were retrospectively examined. Results: Among 355 nodules, 322 (90.7%) were categorized as cystic fluid or benign. The aspirated materials were mainly composed of non-epithelial components, including colloid or proteinaceous materials, foamy histiocytes, and degenerative red blood cells. In original ultrasound reports, the incidence of intermediate and high suspicion was 11.0%. Malignant cells were observed in 21 nodules (5.9%), one-third of which were papillary thyroid carcinomas. The materials aspirated from papillary and follicular thyroid carcinomas exhibited necrotic carcinoma cells derived from infarcted areas. The overall risk of malignancy was 3.9%. The risk of malignancy in nodules interpreted as highly suspicious on ultrasound examination was 37.5%. Conclusion: As clay-like materials aspirated from thyroid nodules were considered sufficient specimens, the recognition contributes to avoiding unnecessary second punctures. The presence of clay-like materials was indicative of the colloid and/or blood components of benign cystic lesions, or, more rarely, of infarcted carcinoma. The ultrasound examination results tended to overestimate nodules. We should reaffirm that on-site gross visual assessment of aspirated materials is a fast and reasonably accurate predictor of the on-site adequacy of the samples.
Most types of thyroid carcinomas express PAX8 transcription factor; however, whether thyroid squamous cell carcinoma (SCC) also expresses PAX8, currently remains unknown. We herein examined the immunoreactivity of PAX8 in SCC of thyroidal and extrathyroidal origin, and discussed the diagnostic significance of PAX8. We immunohistochemically examined specimens from 11 SCC, 22 papillary thyroid carcinoma (PTC), 8 anaplastic thyroid carcinoma (ATC), and 2 mucoepidermoid carcinoma (MEC) cases as well as 5 uterine cervical SCC, 5 esophageal SCC, and 5 pulmonary SCC cases. The rates of PAX8-positive SCC, PTC, ATC, and MEC were 90.9%, 90.9%, 75.0%, and 100%, respectively. Two PAX8-negative PTC cases were cribriform variants. No uterine cervical, esophageal, or pulmonary SCC specimen reacted with PAX8 antibody. Thyroid transcription factor-1 (TTF-1) was positive in 9.1% and 95.5% of SCC and PTC cases, respectively, but negative in all ATC and MEC cases. These results demonstrate that PAX8 staining is useful for distinguishing between primary thyroid SCC and invasion or metastasis from extrathyroidal SCC. We recommend using an immunohistochemical panel of antibodies to PAX8 and TTF-1 to confirm a diagnosis of primary thyroid carcinoma.
