Parathyroid Cystic Adenoma: A Systematic Review and Meta-Analysis

Objective: To review diagnostic imaging modalities for parathyroid cystic adenomas (PCA). Since PCAs are a rare (0.5%-1%) subclass of parathyroid adenomas, and due to their cystic component, imaging modalities known to be efficient for diagnosing solid adenomas might fail in localizing them. Methods: We conducted a systematic review using the PubMed and Cochrane databases for English articles on PCAs published between 1995 and 2020. A meta-analysis of the retrieved data was performed. Results: Overall, 39 studies, reporting on a total of 160 patients, were included in the analysis. Two thirds (68%) of the patients were female, with a mean age of 53.9 years. A single cystic adenoma was detected in 98.1% of cases. The mean blood calcium corrected for albumin level was 12.6 ± 2.7 mg/dL, and the mean parathyroid hormone level was 565.5 ± 523.8 pg/mL. The mean PCA sizes as measured by ultrasound (US), computed tomography (CT), and ex vivo measurement were 4.8 ± 3.6, 5.2 ± 3.2, and 3.5 cm, respectively. The median weight was 8.1 g. PCA was detected in 86% of US examinations; 100% of US-guided fine needle aspiration, 4-dimensional computed tomography (4D-CT), or magnetic resonance imaging examinations; and 61% of 99m-technetium sestamibi scan with single-photon emission computed tomography ((99m)Tc-SPECT). (99m)Tc-SPECT showed a significantly lower diagnostic rate than US (odds ratio, 3.589), US-guided fine needle aspiration, CT combined with 4D-CT, and the combination of US, CT, 4D-CT, and magnetic resonance imaging (P < .001). Conclusion: Although US and 4D-CT showed a significantly high rate in diagnosing PCA, (99m)Tc-SPECT showed a lower PCA diagnostic rate. These findings suggest that larger cystic lesions suspected as PCAs should be further evaluated using 4D-CT rather than (99m)Tc-SPECT.