Abstract
Simple SummaryParathyroid carcinoma (PC) is a rare endocrine malignancy and an uncommon cause of primary hyperparathyroidism. It is more common in older Caucasians, with a slight male predominance. Among the patients with available data in a large national cancer registry of the U.S. population, PC was usually 2–4 cm in size, histologically defined as well-differentiated adenocarcinoma, and localized to the native glands with negative lymph nodes. The overwhelming majority (>95%) of the patients underwent surgery, with the remaining few receiving radiation or chemotherapy. The 5-year survival rate after surgery was 84%. Factors such as large tumor size (>4 cm), older age (>40 years), male sex, Caucasian race, distant spread, and poor tumor differentiation were associated with an increased risk of death.Introduction: Parathyroid carcinoma (PC) is an extremely rare entity, with a frequency of 0.005% of all malignancies. Most data related to this rare disease are limited to case series and a few database studies. We present a large database study that aims to investigate the demographic, clinical, and pathological factors, prognosis, and survival of PC. Methods: Data of parathyroid carcinoma were extracted from the Surveillance, Epidemiology, and End Results (SEER) diagnosed between 1975 and 2016. Results: PC had a slightly higher incidence in men (52.2%, p < 0.005), the majority of cases affected Caucasians (75.4%, p < 0.005), and the mean age at diagnosis was 62 years. Histologically, 99.7% were adenocarcinomas not otherwise specified (p < 0.005), well-differentiated (p < 0.005), and 2–4 cm (p < 0.001) in size among the patients with available data. In cases with staging provided, most PC were organ-confined (36.8%, p < 0.001). Lymph nodes were positive in 25.2% of cases where lymph node status was reported. The main treatment modality was surgery (97.2%), followed by radiation alone (2%), and very few received chemotherapy alone (0.8%), p < 0.005. Five-year follow-up was available for 82.7% of the cases. Those who underwent surgery only or radiation alone had 5-year survivals of 83.8% and 72.2%, respectively (p < 0.037). Multivariable analysis identified tumor size >4 cm, age > 40 years, male sex, Caucasian race, distant spread, and poorly differentiated grade as independent risk factors for mortality (p < 0.001). Conclusion: PC is a very rare tumor mostly affecting Caucasian individuals in the fifth decade. Older age, poor histologic differentiation, and distant metastasis are associated with a worse prognosis. Surgical resection offers the best survival outcome. To better understand the pathogenesis and factors affecting survival, all PC patients should be enrolled in national and international registries.
Highlights
Parathyroid carcinoma (PC) is an extremely rare entity, with a frequency of 0.005% of all malignancies
This study presents one of the largest cohorts of patients with PC, with mean age of diagnosis of 62 ± 10 years, slightly higher incidence in men, 25% with nodal metastasis, and tumor size 4 cm associated with poor outcome
Reports about the impact of nodal involvement on prognosis have been contradictory: Asare et al and other studies performed on large databases reported that survival and recurrence rates are not affected by positive nodal status [1,2,14,18]
Summary
Parathyroid carcinoma (PC) is an extremely rare entity, with a frequency of 0.005% of all malignancies. Most data related to this rare disease are limited to case series and a few database studies. Results: PC had a slightly higher incidence in men (52.2%, p < 0.005), the majority of cases affected Caucasians (75.4%, p < 0.005), and the mean age at diagnosis was 62 years. Five-year follow-up was available for 82.7% of the cases Those who underwent surgery only or radiation alone had 5-year survivals of 83.8% and 72.2%, respectively (p < 0.037). Multivariable analysis identified tumor size >4 cm, age > 40 years, male sex, Caucasian race, distant spread, and poorly differentiated grade as independent risk factors for mortality (p < 0.001). The etiology of PC is mainly unknown; there is an increased risk of parathyroid carcinoma in patients with the hyperparathyroidism-jaw tumor syndrome (HPT-JT) [4]. Clinical features that raise concern for parathyroid malignancy include serum calcium >14 mg/dL, PTH >5–10 times the upper limit of normal or PTH >500 pg/mL, palpable neck mass, concomitant skeletal, renal disease, and features of parathyroid crisis, e.g., altered mental status [10]
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