Parathyroid Carcinoma: A Single-Institution Experience with an Emphasis on Histopathological Features.

Parathyroid carcinoma (PC) is a rare malignancy that poses a diagnostic challenge on histologic examination. We analyzed various clinicopathologic features of PC. Pathology reports and slides were reviewed to evaluate the diagnostic histopathologic features of archived cases of PC from the years of 2004-2018. The study cohort comprised twenty cases of PC. The median age was 49 years (range 21-73 years) with equal gender distribution (M:F = 1:1). Most patients presented with symptoms of hypercalcemia (n = 7, 54%). Serum calcium and serum parathyroid hormone were elevated in all but one patient. The right inferior parathyroid was commonly involved (n = 8/14, 57%). The mean tumor size was 2.4 cm (range 0.8-3.5 cm). On frozen section examination, PC was diagnosed in 8 out of 9 cases. Vascular (n = 19/20, 95%) and soft tissue invasion (n = 10/20, 50%) were the most common characteristic histologic findings. Capsular invasion was identified in all cases. Perineural invasion or metastasis at presentation was absent in all cases. Other histological features noted were intratumoral fibrous bands (70%), nodular growth pattern (70%), moderate nuclear atypia (30%), prominent nucleoli (20%), and necrosis (20%). Regional lymph nodes were negative for metastatic disease in all cases (n = 10). Eight out of 16 patients received adjuvant radiotherapy. Follow-up was available in 16 cases (median 21.5 months). Two patients died of disease. Vascular and soft tissue invasion are the most common diagnostic histologic features of PC. Capsular invasion is important to distinguish PC from its benign counterparts. Intraoperative frozen section examination can be used for accurate diagnosis and surgical management.

Anaplastic thyroid carcinoma with rhabdoid phenotype: An unusual case and a comprehensive review.

Anaplastic thyroid carcinoma (ATC) is a highly aggressive thyroid malignancy predominantly affecting the elderly with a fatal outcome. ATC with rhabdoid phenotype is a rare variant, with only a few cases reported in the literature to date. We herein report a case of a 44-year old female diagnosed as ATC with rhabdoid phenotype. She had a slow-growing neck mass with no gross extrathyroidal extension (ETE) or nodal/distant metastasis at presentation. Computed tomography of the neck showed a well-defined heterogeneously hypodense nodule in the right lobe of the thyroid. On cytology, a diagnosis of papillary thyroid carcinoma (PTC) with possible anaplastic transformation was made based on the presence of vague papillae with focal nuclear features of PTC and atypical pleomorphic/rhabdoid cells. The total thyroidectomy specimen showed a relatively circumscribed lesion with no gross ETE. Histopathological examination revealed sheets of rhabdoid cells with a focus of poorly differentiated thyroid carcinoma. On immunohistochemistry, rhabdoid cells were positive for AE1/AE3, focally positive for PAX8 and were negative for TTF-1, synaptophysin, desmin, myogenin, S100P, and SMA. The neck lymph nodes were non-metastatic. The patient was further treated with adjuvant radioactive iodine. Four-months post-operatively, the patient developed pulmonary metastasis which on biopsy examination revealed metastatic ATC. Apart from being a rare tumor type, this case is unusual with its presentation too; wherein, unlike described earlier in the literature the patient had a relatively mitigated clinical course with no gross ETE or nodal/distant metastatic disease. We also review the relevant literature along with this case.