August 2003: 47‐year‐old female with a 7‐year history of osteomalacia and hypophosphatemia

Abstract

The August 2003 COM. A 47-year-old woman presented with a long history of muscle pain, weakness, and visual disturbances. Over the last year, she developed diplopia and left sixth nerve palsy. No other neuro-ophthalmologic abnormalities were found. Past medical and family history was unremarkable. Laboratory investigation disclosed hypophosphatemia, phosphaturia, elevated serum alkaline phosphatase activity, and normal serum calcium levels. CT scans showed a lobulated mass arising on the meningeal surface of the cavernous sinus, measuring 3x 2 x 2 cm. The lesion was partially resected and microscopic examination revealed a highly vascularized tumor composed of primitive mesenchymal cells arranged whether in a patternless-pattern or surrounding thin-walled, branching vascular spaces and thick-walled hyalinized vessels. Other eye-catching features were microcystic areas, multinucleated osteoclastic-like giant cells, scattered islands of mature adipocytes, foci of hemorrhage, thrombosed medium-sized-to-large vessels, and hemosiderin-laden macrophages. After surgery, the patient recovered from the muscle pain and weakness, with a significant improvement of serum calcium and alkaline phosphatase levels and phosphate blood levels. Taken together, the clinical and pathologic features were consistent with a diagnosis of phosphaturic mesenchymal tumor (mixed connective tissue variant) of the cavernous sinus in a setting of oncogenic osteomalacia. No further treatment was carried out. The patient has been followed for the last 4 years with no evidence of recurrent disease. Oncogenic osteomalacia is a rare clinical entity characterized by hypophosphatemia, phosphaturia, and a low concentration of 1,25-dihydroxyvitamin D(3) caused by a neoplasm. Pathologists should be aware of this entity, because surgical excision of the tumor is usually curative.

Oncogenic Osteomalacia: Exact Tumor Localization by Co-Registration of Positron Emission and Computed Tomography

“…Tumors associated with OOM have been reported to occur at many different locations without a discernible prevalence in location. (17)(18)(19)(20) Thus, other than the recognition of the disease itself, detection of the tumor is by far the major challenge in the treatment of this disorder. Failure to discover the tumor may lead to a delayed diagnosis up to several years from the onset of symptoms.…”

Intracranial phosphaturic mesenchymal tumor, mixed connective tissue variant presenting without oncogenic osteomalacia

“…In patients with tumor-induced osteomalacia, resection of the causative tumor is curative and laboratory values including serum FGF-23 levels can be followed to monitor for tumor recurrence. [56891113] While our patient did not have osteomalacia or abnormal laboratory values, her serum FGF-23 level was normal post-operatively and could potentially indicate tumor recurrence if it was elevated in the future. This will be reassessed in follow up if any of her future MRIs demonstrates evidence of recurrence.…”

“…[5] An intracranial occurrence is extremely rare, with only two other reports of intracranial PMTMCT in the literature. [311] Our case represents only the third intracranial PMTMCT reported and the first that was not associated with osteomalacia.…”

“…Intracranial occurrence of this tumor is extremely rare and only two cases of an intracranial PMTMCT have been described in the literature. [311] It is not described in the World Health Organization Classification of Tumors of the Central Nervous System. [7]…”

Definitive surgical treatment of osteomalacia induced by skull base tumor and determination of the half-life of serum fibroblast growth factor 23

“…Intracranial FGF23-producing PMTMCT is extremely rare and, to the best of our knowledge, only 17 cases have been reported in the literature to date (Table 1) [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. It tends to affect sterically complicated areas such as the anterior skull base.…”