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Open access

Daniela Gallo, Sara Rosetti, Ilaria Marcon, Elisabetta Armiraglio, Antonina Parafioriti, Graziella Pinotti, Giuseppe Perrucchini, Bohdan Patera, Linda Gentile, Maria Laura Tanda, Luigi Bartalena, and Eliana Piantanida

Summary

Brown tumors are osteoclastic, benign lesions characterized by fibrotic stroma, intense vascularization and multinucleated giant cells. They are the terminal expression of the bone remodelling process occurring in advanced hyperparathyroidism. Nowadays, due to earlier diagnosis, primary hyperparathyroidism keeps few of the classical manifestations and brown tumors are definitely unexpected. Thus, it may happen that they are misdiagnosed as primary or metastatic bone cancer. Besides bone imaging, endocrine evaluation including measurement of serum parathyroid hormone and calcium (Ca) levels supports the pathologist to address the diagnosis. Herein, a case of multiple large brown tumors misdiagnosed as a non-treatable osteosarcoma is described, with special regards to diagnostic work-up. After selective parathyroidectomy, treatment with denosumab was initiated and a regular follow-up was established. The central role of multidisciplinary approach involving pathologist, endocrinologist and oncologist in the diagnostic and therapeutic work-up is reported. In our opinion, the discussion of this case would be functional especially for clinicians and pathologists not used to the differential diagnosis in uncommon bone disorders.

Learning points:

  • Brown tumors develop during the remodelling process of bone in advanced and long-lasting primary or secondary hyperparathyroidism.

  • Although rare, they should be considered during the challenging diagnostic work-up of giant cell lesions.

  • Coexistence of high parathyroid hormone levels and hypercalcemia in primary hyperparathyroidism is crucial for the diagnosis.

  • A detailed imaging study includes bone X-ray, bone scintiscan and total body CT; to rule out bone malignancy, evaluation of bone lesion biopsy should include immunostaining for neoplastic markers as H3G34W and Ki67 index.

  • If primary hyperparathyroidism is confirmed, selective parathyroidectomy is the first-line treatment.

  • In advanced bone disease, treatment with denosumab should be considered, ensuring a strict control of Ca levels.

Open access

Zaina Adnan, David Nikomarov, Michal Weiler-Sagie, and Noga Roguin Maor

Summary

Phosphaturic mesenchymal tumor (PMT) represents a rare cause of osteomalacia. The clinical signs and symptoms are vague and these lead to diagnosis delay. In the presence of hypophosphatemia and relatively high urine phosphate excretion, this entity should be taken into consideration in the deferential diagnosis of osteomalacia. In the present article, we report 81-year-old man presented to our clinic for evaluation due to osteopenia. His laboratory results disclosed hypophosphatemia, relatively increased urine phosphate excretion and increased level of intact fibroblast growth factor 23 (FGF23). A 68Gallium DOTATATE PET/CT revealed pathological uptake in the upper aspect of the left shoulder adjacent to the coracoid process. For suspected PMT a wide resection of the tumor was performed and pathological findings were consistent for PMT. Laboratory tests were normalized postoperatively. Reviewing the literature, we had identified 33 reported cases of PMTs among elderly patients age ≥70 years. Unlike previously reported data, where tumors predominantly localized in the lower extremities and pelvis, our search disclosed a high rate of tumor localization (10 cases – 33.3%) in the head with equal number of tumors (14 cases – 42.4%) localized in the head and upper extremity as well as in pelvis and lower extremity. The present case describes unique tumor localization in an elderly patient and our literature search demonstrated for the first time a high rate of tumor localization in the head among this group of patients.

Learning points:

  • PMTs represent a rare entity that should be considered in the differential diagnosis of elderly patients presented with persistent hypophosphatemia.

  • Unlike previously reported data, head and neck tumor localization is frequent among elderly patients.

  • 68Gallium-conjugated somatostatin peptide analogs, such as 68Ga-DOTATATE PET/CT demonstrated the greatest sensitivity and specificity for tumor localization in patients with phosphaturic mesenchymal tumors (PMTs).

  • Wide tumor resection using intraoperative ultrasound is of major importance in order to ensure long-term cure.