Woman, 61 years old. In 1991 acute promyelocytic leukemia, treated with chemotherapy and autologous bone marrow transplantation, negative follow up. In 2015 left lower parathyroidectomy for primary hyperparathyroidism.

In 2021, report of hypercalcemia of 11.3 mg/dL, PTH 101 ng/L, s-25OH-Vit.D 25.9 ug/L and suspicious ultrasound finding in the left parathyroid lodge, suggestive of relapsed hyperparathyroidism. Reoperation is proposed, pending instrumental confirmation of the localization: (99m)Tc-MIBI is performed, which is not decisive. F18-choline PET/MRI reveals tracer hyperaccumulation in a node measuring 7 x 4 mm in the mid-upper third middle of the left lobe of the thyroid gland, referable to a hyperfunctioning parathyroid, and also highlights tracer uptake in the left upper mediastinum.

Simultaneous findings on blood tests of mild anemia (Hb 10.9 g/dL) and thrombocytopenia (PLT 68000/uL). Given the suspicious mediastinal finding and the abnormalities of the blood count, as per hematological recommendation the patient undergoes a sternal bone marrow biopsy, revealing AREB-type myelodysplasia. The operation is suspended and the patient is treated with chemotherapy followed by allogeneic bone marrow transplantation. After resolution of the haematological condition, the patient continues the endocrinological evalutation. In November 2023, following repeating a cervical ultrasound, which confirms an upper left retrothyroid lesion measuring 13 x 16 x 7 mm, the patient underwent upper left parathyroidectomy. Intraoperative PTH levels were 184 ng/L and 40 ng/L, postoperative. Histological examination confirmed an adenoma of the parathyroid.

This case report highlights how F18-choline PET-MRI may have a sentinel role in the diagnosis of other tumor pathologies.