Synchronous Multiple Parathyroid Carcinoma: A Challenging Diagnosis Influencing Optimal Primary Treatment – a Literature Review

Synchronous multiple parathyroid carcinoma (SMPC) is a rare condition within the already uncommon landscape of parathyroid malignancies, which comprise less than 1% of sporadic primary hyperparathyroidism (sPHP) cases. To date, only seven cases of SMPC in sPHP have been documented. This exceptional rarity complicates both the diagnostic process and therapeutic decision-making. Clinically, parathyroid carcinoma (PC) typically presents as a single mass determining severe symptoms. However, no single clinical, biochemical, or imaging feature allows for definitive preoperative diagnosis. Imaging modalities such as ultrasound (US) and Sestamibi (MIBI) scan exhibit variable sensitivity and may overlook multi-gland involvement. Histopathological examination remains the only reliable diagnostic method. Management strategies are also controversial: while some advocate for conservative surgery, en bloc resection is generally recommended for its association with improved local control and disease-free survival. Given the exceptional occurrence of SMPC, there is a lack of standardized protocols to manage PC in case of synchronous and multiple gland involvement. Early multidisciplinary evaluation and individualized treatment planning are therefore crucial. This review aims to synthesize currently available knowledge about SMPC to assist clinicians with the limited data available and guide decision-making in the management of this rare and challenging entity.