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

Abstract

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.

Parathyroid Carcinoma: a Review

“…However, the utility of frozen section has largely met with disrepute due to a reported low accuracy of a diagnosis of PC [42,43]. This notion has recently been challenged by the results of the study from our institute where 8 out of 9 cases were accurately suspected on frozen section to be PC [39]. The authors conclude that a dedicated oncology center with expertise to treat and diagnose PC coupled with experienced head and neck pathologists significantly impact the accuracy of intra-operative diagnosis.…”

“…Large size (as compared to the normal weight of Parathyroid glands), and peroperative adherence to adjacent structures are some of the important characteristics of PC. T-size greater than 3 cm in a hypercalcemic patient with hyperparathyroidism is highly suggestive of PC, whereas a size greater than 4 cm is associated with an increased risk of death (Hazard Ratio 1.91, 95% Confidence Interval 1.35-2.69) [34]. In 1973, Schantz and Castleman proposed the criteria for defining parathyroid carcinoma [8] that included fibrous bands arranged in a trabecular design, mitotic activity, capsular invasion, and vascular invasion.…”

“…The extent of capsular invasion and capsular invasion without infiltration into adjacent structures had not been clarified [41]. The abstruse importance of capsular invasion was addressed by the recent study from our institute which has shown that capsular invasion was present in all cases of PC; infact it was the only feature that was common amongst all 20 cases of PC, thus reiterating the need to document capsular invasion, and perform additional sampling/sectioning to rule out a PC in cases with capsular invasion without invasion of the surrounding tissues [39].…”

“…Therefore, the surgeon should be vigilant to identify the sinister features of malignancy intraoperatively to perform adequate surgery at the time of initial management. Carcinoma is usually bigger, irregular whitish mass, with a fibrous capsule that may adhere or infiltrate the surrounding fibrofatty tissue or thyroid lobe [34,50]. The presence of metastatic nodes is pathognomonic of malignancy.…”

Main parathyroid tumors

“…Поэтому хирург должен оперировать с особой внимательностью для того, чтобы вовремя выявить признаки злокачественного новообразования во время операции и выполнить адекватный объем резекции. Рак обычно представляет собой более крупное белесоватое образование неправильной формы с фиброзной капсулой, которая может срастать-ся с окружающей фиброзно-жировой тканью или долей щитовидной железы или инфильтрировать их [58,59]. Наличие метастатических узлов также является патогномоничным признаком злокачественности.…”