(1) Background: Parathyroid cystic adenomas (PCA) are rare entities representing only 0.5–1% of parathyroid adenomas, accounting for 1–2% of cases of primary hyperparathyroidism (PHPT). The purpose of this study was to compare classical and functional/secreting cystic parathyroid lesions and identify risk factors for severe hypercalcemia; (2) Methods: A total of 17 patients with PHPT and parathyroid cysts (study group) were compared with the group of 100 patients with hyperparathyroidism caused by adenoma or hyperplasia (control group). In both groups the majority were women (88% vs. 12%, with gender ratio 7, 3:1). The patients were examined preoperatively and postoperatively: PTH, creatine, calcium and phosphate serum and urine concentrations and calcidiol serum levels were assessed; (3) Results: Patients with parathyroid cyst had statistically higher PTH and calcium serum concentration, higher calciuria and lower serum phosphate concentration. There were no statistically significant differences in the concentration of creatine in serum and urine and tubular reabsorption of phosphorus (TRP); (4) Conclusions: Due to higher PTH and calcium levels, cystic parathyroid adenomas could be one of the rare risk factors for severe hypercalcemia and hypercalcemic crisis which can be life threatening.

Patient: Female, 51-year-old (was first diagnosed as 23-year-old) Final Diagnosis: Parathyroid carcinoma Symptoms: Hypercalcemia • hypercalcemic shock • nephrolithiasis Medication: — Clinical Procedure: Pharmacological treatment • surgery and radiotherapy Specialty: Endocrinology and Metabolic • Oncology Objective: Rare disease Background: Parathyroid carcinoma (PC), accounting for 0.005% of all cancers, is responsible for less than 1% of all cases of primary hyperparathyroidism, and equally affects males and females, usually in 4 th or 5 th decades of life. PC can occur sporadically and can be associated with congenital genetic syndromes such as hyperparathyroidism-jaw tumor syndrome (HPT-JT), isolated familial hyperparathyroidism, or multiple endocrine neoplasia 1 and 2 syndromes. Surgery is the main treatment, with a limited role of radio- and chemotherapy, which allows 49–77% of patients to survive 10 years. In this work we report the case of a patient with parathyroid carcinoma, whose treatment required 13 surgeries over a period of 27 years, together with radiotherapy and pharmacological treatment. Case Report: A 51-year-old woman was first diagnosed with primary hyperparathyroidism in 1993 at the age of 23. From 1993 to present, she underwent 13 surgeries and 33 courses of radiotherapy due to recurrent lesions, which initially had a character of parathyroid adenomas, then parathyromatosis, and finally were diagnosed as parathyroid carcinoma. The patient also required and currently requires complex pharmacological treatment to control the calcemia and manage the complications of the primary disease. Supervision by the multidisciplinary professional medical team allows the patient to lead a normal life with good control of the disease. Conclusions: Parathyroid carcinoma is a rare disease with a number of complications; however, obtaining satisfactory long-term survival with acceptable quality of life is achievable.

Case series Patients: Male, 57-year-old • Male, 42-year-old • Female, 45-year-old • Male, 42-year-old Final Diagnosis: Brown tumor • hyperparathyroidism Symptoms: Brown tumor • hypercalcemia Medication: — Clinical Procedure: — Specialty: Endocrinology and Metabolic Objective: Rare disease Background: Brown and jaw tumors are rare entities of poorly understood etiology that are regarded as end-stage of bone remodeling in patients with long-lasting and chronic hyperparathyroidism. Jaw tumors are mainly diagnosed in jaw tumors syndrome (HPT-JT syndrome) and are caused by mutation in the CDC73 gene, encoding parafibromin, a tumor suppressing protein. The aim of this work is to present 4 cases of patients in whom the genetic mutation of the CDC73 gene and clinical presentation coexist in an unusual setting that has not yet been described. Case Reports: We present cases of 4 patients with primary hyperparathyroidism. Three were diagnosed with brown tumors (located in long bones, ribs, iliac, shoulders) and 1 with brown and jaw tumors. Expression of parafibromin in affected parathyroid tissues were analyzed. In patients without positive parafibromin staining, we searched for CDC73 mutation using next-generation sequencing. Parafibromin staining was positive in 1 patient with brown tumors and was negative in 2 individuals with brown tumors and 1 with brown and jaw tumors. CDC73 mutation was detected in two-thirds of patients (60%) with negative staining for parafibromin and brown tumors. MEN1 mutation was found in the patient with brown tumor and positive staining for parafibromin. Conclusions: Patients with hyperparathyroidism and coexistence of brown tumors or jaw tumors might have decreased expression of parafibromin in parathyroid adenoma tissue, which might be caused by CDC73 mutation and suggest a genetic predisposition. Further research on much larger study groups is needed.