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Difficult Diagnostic Cases

CASE 3. Oncogenic Osteomalacia Associated With Hemangiopericytoma Localized by Octreotide Scan

Tripler Army Medical Center, Honolulu, HI

A 37-year-old man presented with chronic lower back and chest wall pain. Technetium-99m methylenediphosphonate whole-body scinitigraphy was performed during the initial evaluation. A posterior image revealed increased radiotracer uptake involving the ribs, lumbar vertebrae, right humerus, right radius, bilateral tibiae, and bilateral feet (Fig 1). Preliminary labs revealed decreased serum phosphate with elevated alkaline phosphatase and parathyroid hormone. The initial differential diagnosis included metastatic disease and metabolic bone disorders. Further evaluation with x-rays, magnetic resonance imaging, and computed tomography demonstrated findings consistent with osteomalacia. A sagittal proton weighted–magnetic resonance image demonstrated a linear low signal at the medial aspect of the proximal tibia with associated bone marrow edema (Fig 2A; arrow). This is consistent with a Looser's zone (cortical insufficiency fracture). A sagittal T2-weighted image of the lumbar spine demonstrated abnormal signal throughout the bone marrow (Fig 2B; arrows). Note the absence of mass effect or cortical destruction. The differential diagnosis for this abnormal signal included multiple insufficiency fractures. Screening labs revealed decreased serum phosphate, decreased renal tubular resorption of phosphate, increased alkaline phosphatase, and increased parathyroid hormone. These findings, combined with the imaging findings of osteomalacia, led to the diagnosis of oncogenic osteomalacia.¹ At the time of diagnosis, no obvious primary source was noted and an Indium-111 (In-111) –labeled pentetreotide whole-body scan (octreotide scan) was performed to evaluate for a somatostatin-receptor–positive tumor. Twenty-four-hour anterior view of the pelvis following administration of 5.5 mCi In-111 pentetreotide demonstrated an abnormal focus of increased radiotracer uptake in the region of the left grown (Fig 3A; arrow). Single photon image computed tomography (SPECT) confirmed the subcutaneous location of the lesion (Fig 3B; arrow). The midline areas of radiotracer uptake corresponded to normal uptake in the bladder (anterior) and rectum (posterior). The octreotide scan established the presence of a somatostatin-receptor–positive tumor. Surgical resection of the tumor was performed. Pathology revealed a mesenchymal tumor consistent with hemangiopericytoma, the most common cause of oncogenic osteomalacia.^1-2 Microscopic examination showed numerous thin-walled branched vessels with intervening uniform tumor cells and focal osseous metaplasia (Fig 4). Following the surgical resection, the patient's serum phosphate and renal tubular resorption of phosphate normalized.

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Note: The views expressed in this manuscript are those of the authors and do not reflect the official policy or position of the Department of the Army, Department of Defense, or the US Government.

Authors' Disclosures of Potential Conflicts of Interest

The authors indicated no potential conflicts of interest.

REFERENCES

1. Seufert J, Ebert K, Muller J, et al: Octreotide therapy for tumor-induced osteomalacia. N Engl J Med 345 : 1883 -1888, 2001[Free Full Text]

2. Sundaram M, McCarthy EF: Oncogenic osteomalacia. Skeletal Radiol 29 : 117 -124, 2000[CrossRef][Medline]

3. Jan de Beur SM, Streeten EA, Civelek AC, et al: Localization of mesenchymal tumors by somatostatin receptor imaging. Lancet 359 : 761 -763, 2002[CrossRef][Medline]

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This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Save to my personal folders Download to citation manager Rights & Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Auethavekiat, P. Articles by Berenberg, J. L. Search for Related Content PubMed PubMed Citation Articles by Auethavekiat, P. Articles by Berenberg, J. L. Social Bookmarking                            What's this?