巨大機能性副甲状腺嚢胞「スノー・ストーム」現象を伴う：稀な臨床的および画像的提示

Giant functional parathyroid cysts (PCs) are extremely rare and can present significant diagnostic challenges. We report a case of a 31-year-old woman with primary hyperparathyroidism (PHPT) due to a giant PC, which presented with biochemical features of hyperparathyroidism, compressive symptoms in the neck structures, and a unique ultrasonographic "snowstorm" pattern, mimicking thyroid pathology. Diagnosis was confirmed postoperatively by histopathology. This case highlights the importance of including PCs in the differential diagnosis of cystic neck masses, particularly when biochemical and imaging findings are discordant.