Abstract Neurofibromatosis type 1 (NF 1) is a syndrome with a predisposition for benign and malignant tumor de- velopment. Of the malignant neoplasms, osteogenic sarco- mas are rare but have been described. There are some re- ports of patients with neurofibromatosis type 1 with a para- thyroid adenoma and hyperparathyroidism. Also, there are studies that imply that the parathyroid hormone plays a role in the regulation and modulation of oseogenic sar- comas in vitro. We report about a 50-year-old female suf- fering from neurofibromatosis type 1, with a 3-year docu- mented history of untreated hyperparathyroidism and a parathyroid adenoma. The patient developed a mandibular osteogenic sarcoma. To our knowledge, this is the first re- ported case occurring in the mandible. The unusual tumor site for a patient with neurofibromatosis type 1, the conju- gation with hyperparathyroidism and the rapid growth of an osteogenic sarcoma are intriguing. Keywords Neurofibromatosis type 1 · Hyperparathyroidism · Osteosarcoma Introduction: Osteosarcoma of the jaws is relatively rare and accounts for 6.5% of all sarcomas in the entire body. Nevertheless, it is the most common malignancy of the mandible [1, 5]. The transmission of the neurofibromatosis type 1 (NF 1) syndrome is autosomal dominant. This syndrome has a pre- disposition for benign and malignant tumor development. Of those malignant neoplasms, osteogenic sarcomas are rare [12]. To our knowledge, there are no reports of a NF 1 patient with an ostegenic sarcoma of the mandible. However, there are reports of patients with NF 1 with para- thyroid adenomas causing hyperparathyroidism [4, 10]. Parathyroid hormone (PTH) is a modulator of osteoblastic activity and plays an important role in the regulation of rat and human osteosarcoma cells [2, 6, 8, 11]. We report a case of a 50-year-old female suffering from NF 1, with a 3-year documented history of untreated hyperparathyroid- ism, parathyroid adenoma and rapid growth of a mandib- ular osteogenic sarcoma. The correlation between NF 1, hyperparathyroidism due to a parathyroid adenoma and rapid development of an osteogenic sarcoma of the man- dible is rare and should raise further questions. Case report A 50-year-old female with NF 1 was referred to our outpatient clinic because of a swelling in her left parotid region. She first had noticed her swollen cheek several months earlier but asked for a medical consultation only after severe pain had begun. The patient had a documented history of hypercalcemia and hyperparathy- roidism for 3 years prior to admission, but she had sought no med- ical attention nor received any treatment during that period. Her family history revealed that two of her children and two brothers suffered from NF 1. None of them had a malignant neoplasm. A CT scan demonstrated a mass occupying the left parotid re- gion, involving the ramus of the mandible and reaching into the in- fratemporal region. The elevated blood calcium and parathyroid hormone, CT scan of the neck, ultrasound of the neck and Tc-99 MIBI scan were in accordance with the diagnosis of a parathyroid adenoma. CT scans of the chest, mediastinum and abdomen were normal. A coarse-needle biopsy from the mass showed spindle and oval cells with few mitotic figures. Some multinucleated cells were also in the myxoid stroma. The cell stains were positive for vimentin, while negative for S-100 protein, keratin, and CD-45RA. The patient underwent a total parotidectomy and partial mandibulectomy. The surgical findings were of a tumor with a size of 5 × 4×7 cm, partially encapsulated and involving the mandible. It seemed to be adherent to its capsule but not to involve the Udi Cinamon · Ilana Avinoach · Moshe Harell Neurofibromatosis type 1, hyperparathyroidism, and osteosarcoma: interplay? Eur Arch Otorhinolaryngol (2002) 259 : 540–542 DOI 10.1007/s00405-002-0497-3 Received: 7 March 2002 / Accepted: 21 May 2002 / Published online: 9 July 2002 HEAD AND NECK ONCOLOGY U. Cinamon (✉) · M. Harell Department of Otolaryngology, Head and Neck Surgery, The Edith Wolfson Medical Center, 58100 Holon, Israel e-mail: udicin@hotmail.co.il, Tel.: +972-53-872759, Fax: +972-9-7679605 I. Avinoach Department of Pathology, The Edith Wolfson Medical Center, Holon, Israel U. Cinamon Ear Research Laboratory, Department of Bio-medical Engineering, Tel Aviv University, Tel Aviv, Israel © Springer-Verlag 2002