Case 360 -- Osteomalacia and Hypophosphatemia

Contributed by Jorge S Reis-Filho, MD, 1 Maria E Paiva, MD2 and José M Lopes, MD, PhD 1,2,3
  1 Institute of Molecular Pathology and Immunology, University of Porto (IPATIMUP), Portugal
2 Department of Pathology, São João Hospital, Porto, Portugal
3 Department of Pathology, Porto Medical Faculty, University of Porto, Portugal
Published on line in August 2003


A woman in her 40s presented with a 7-year-history of muscle pain and weakness. She also complained of visual disturbances over the last five years that resulted in diplopia over the last year. Past medical and family histories were unremarkable. Neuro-ophthalmologic examination revealed left sixth nerve palsy. No other neurological abnormality was found. Laboratory investigation disclosed hypophosphatemia (12.3mg/L - normal, 27 to 45mg/L), phosphaturia, elevated serum alkaline phosphatase activity (345 IU/L - normal, 39 to 117 IU/L), and normal serum calcium levels (4.87mEq/L - normal, 4.20 to 5.40 mEq/L). No other clinical or metabolic abnormalities were detected. Computed tomographic scans showed a mass with lobulated borders arising on the meningeal surface of the cavernous sinus, measuring 3x2x2 cm (Figure 1). The radiological appearance was suggestive of cavernous-sinus meningioma. At surgical removal, a highly vascularized tumor was observed; owing to the proximity of the carotid artery and to the remarkable vascularization of the tumor, a complete resection was not possible. No radiotherapy or chemotherapy was carried out. Two weeks after the surgery, the patient had no complaints regarding muscle pain or weakness. Laboratory work-up showed marked improvement of serum calcium and alkaline phosphatase levels (4.49mEq/L and 192UI/L, respectively), and consistent increase in phosphate blood levels (16.6mg/L). The patient has been followed for the last four years with a marked improvement in her metabolic status (only with a mild hypophosphatemic metabolic state), and without any complaint of symptoms recurrence.


Multiple fragments of firm, fleshy and white tissue with scattered red-brown areas, measuring 2.5x1.8x1.5 cm, were received for pathological examination. Histologically, the tumor was composed of primitive mesenchymal cells, with plump, ill-defined, scant cytoplasm, oval-to-elongated nuclei, showing finely granular chromatin and indistinct nucleoli (Figure 2). These cells were predominantly arranged in a patternless-pattern (Figure 2). In some areas, cells were disposed around thin-walled, branching vascular spaces (Figure 3). Numerous thick-walled vessels with hyalinized walls were found. A remarkable feature was the presence of microcystic areas, scattered osteoclastic-like multinucleated giant cells (Figure 4), and scattered islands of mature adipocytes (Figure 5). Foci of hemorrhage (Figure 3), thrombosed medium-sized-to-large vessels, and hemosiderin-laden macrophages were also observed (Figures 2 and 3).

Tumor cells were strongly immunoreactive for vimentin, but were negative for actin HHF35, desmin, S100 protein, EMA, and CD34. Osteoclastic-like giant cells and macrophages were positive for CD68. Endothelial cells showed discrete immunoreactivity for CD34. No positivity for desmin, actin HHF35, EMA, and S100 protein was observed.


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