Is atypical parathyroid tumor a different clinical entity than parathyroid adenoma and carcinoma? A retrospective review of a large single-center case series - Report - MDSpire
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Is atypical parathyroid tumor a different clinical entity than parathyroid adenoma and carcinoma? A retrospective review of a large single-center case series
Clinical Report: Distinguishing Atypical Parathyroid Tumors from Adenomas and Carcinomas
Overview
This retrospective study analyzed 352 patients with single-gland primary hyperparathyroidism (PHPT) to compare atypical parathyroid tumors (APT) with parathyroid adenomas (PA) and carcinomas (PC). Findings highlight that APTs exhibit histological features overlapping with carcinomas but lack definitive invasive characteristics, underscoring the need for tailored follow-up strategies.
Background
Primary hyperparathyroidism is characterized by excessive parathyroid hormone secretion leading to hypercalcemia and can present as symptomatic or asymptomatic disease. Single-gland pathologies include parathyroid adenoma, atypical parathyroid tumor, and carcinoma, with APT defined as a neoplasm of uncertain malignant potential. Histologically, APTs share features with carcinomas but lack unequivocal invasion or metastasis. Accurate differentiation is critical for prognosis and management.
Data Highlights
Parameter
Reference Range
Definition/Notes
Serum Calcium
8.4–10.2 mg/dl
Hypercalcemia indicates PHPT
PTH
8.7–79.6 pg/ml
Elevated in PHPT
Phosphorus
2.5–4.5 mg/dl
Measured pre-operatively
24-h Urinary Calcium
>250 mg women, >300 mg men
Defines hypercalciuria, risk factor for nephrolithiasis
Ki67 Index
5-6%
>6% associated with aggressive tumor behavior
Post-op Hypocalcemia
<8.4 mg/dl
With normal PTH
Hypoparathyroidism
PTH <8.7 pg/ml and Ca <8.4 mg/dl
Transient if <6 months, permanent if >6 months
Key Findings
APT incidence ranges from 0.5% to 4.4%, with female predominance.
APT histology shows features typical of carcinoma (cytologic atypia, fibrosis, high mitotic activity) but lacks definitive capsular or vascular invasion.
Ki67 proliferation index >6% correlates with aggressive parathyroid carcinoma; adenomas typically have <5% Ki67 positivity.
No specific immunohistochemical marker currently distinguishes APT; diagnosis relies on histopathology and clinical context.
Retrospective analysis included 352 single-gland PHPT patients, excluding multiglandular disease, with standardized surgical and pathological evaluation.
Postoperative complications such as hypocalcemia and hypoparathyroidism were defined and monitored according to biochemical criteria and duration.
Clinical Implications
Clinicians should recognize atypical parathyroid tumors as distinct entities with uncertain malignant potential requiring careful histopathological assessment. Given the overlap with carcinoma features but absence of invasive behavior, tailored postoperative surveillance is essential to detect persistence or recurrence. The Ki67 index may aid in risk stratification but is not definitive for APT diagnosis.
Conclusion
Atypical parathyroid tumors represent a histologically intermediate group between adenomas and carcinomas, necessitating nuanced diagnostic and follow-up approaches. Further research is needed to identify specific markers and optimize management protocols.
References
WHO 2022 -- Classification of Endocrine Tumors
Abbona et al. -- Ki67 Proliferative Index in Parathyroid Lesions
ISS/AME/SIOMMMS Guidelines 2023 -- Definitions of Persistent and Recurrent PHPT
