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CASE REPORT
Year : 2014  |  Volume : 29  |  Issue : 3  |  Page : 163-164  

Non-ossifying fibroma mimicking distant metastasis of osteosarcoma on 99m Tc-methylene diphosphonate bone scintigraphy: Diagnosis with single photon emission tomography/computed tomography


Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India

Date of Web Publication11-Jul-2014

Correspondence Address:
Punit Sharma
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi - 110 029
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-3919.136573

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   Abstract 

Non-ossifying fibromas (NOFs) are benign bone lesions with variable appearance on bone scintigraphy. Single photon emission tomography/computed tomography (SPECT/CT) can help in accurate characterization of these lesions. We present a case of 14-year-old boy with recurrent osteosarcoma where NOF was mimicking distant metastasis on 99m Tc-methylene diphosphonate bone scintigraphy. SPECT/CT was able to correctly characterize the lesion as NOF, thereby altering the management.

Keywords: Bone scintigraphy, metastasis, non-ossifying fibroma, single photon emission tomography/computed tomography


How to cite this article:
Sharma P, Singh H, Bal C, Kumar R. Non-ossifying fibroma mimicking distant metastasis of osteosarcoma on 99m Tc-methylene diphosphonate bone scintigraphy: Diagnosis with single photon emission tomography/computed tomography. Indian J Nucl Med 2014;29:163-4

How to cite this URL:
Sharma P, Singh H, Bal C, Kumar R. Non-ossifying fibroma mimicking distant metastasis of osteosarcoma on 99m Tc-methylene diphosphonate bone scintigraphy: Diagnosis with single photon emission tomography/computed tomography. Indian J Nucl Med [serial online] 2014 [cited 2019 Dec 7];29:163-4. Available from: http://www.ijnm.in/text.asp?2014/29/3/163/136573


   Introduction Top


Bone scintigraphy is a commonly used investigation for work-up of bone metastasis in patients with known malignancy. Although it is exquisitely sensitive, its limited specificity remains a concern. A wide range of pathologies including benign tumors, infections, trauma, etc., can mimic metastasis on bone scintigraphy. Recently, introduction of hybrid single photon emission tomography/computed tomography (SPECT/CT) and its use in bone imaging has been shown to improve specificity of bone scintigraphy. We here present a case where non-ossifying fibroma (NOF) was masquerading as metastasis on bone scintigraphy in an osteosarcoma patient. SPECT/CT helped in making the correct diagnosis.


   Case report Top


The present case report is about a 14-year-old male patient with parosteal osteosarcoma of the right proximal femur, who had undergone surgical resection with intramedullary nailing. At routine follow-up 16 months later, recurrence was noted at local site. He was planned for a second surgery. The patient also gave a complaint of pain around the right knee. To rule out metastasis or infection the treating physician requested bone scintigraphy. Three phase 99m Tc-methylene diphosphonate bone scintigraphy was carried out [Figure 1]. It showed mildly increased flow [Figure 1]a, arrow and pool [Figure 1]b and c, arrow activity in the region of right lower femur. Delayed image revealed focal tracer uptake in lower shaft of right femur [Figure 1]d and e, arrow. To characterize this lesion SPECT/CT was performed. CT [Figure 1]f-h and SPECT/CT [Figure 1]i-k images showed a sharply demarcated, asymmetrical, multiloculated, cortical based radiolucent lesion with sclerotic margins, located in the right femoral metaphysis and showing increased radiotracer uptake (arrow). These findings were classical for a NOF. In addition, local recurrence was seen in right proximal femur [Figure 1]d and e, broken arrow] and no other site of skeletal metastasis was seen. The patient underwent re-operation and is undergoing adjuvant chemotherapy. As the NOF was asymptomatic, it required no treatment.
Figure 1: Three phase 99mTc-methylene diphosphonate bone scintigraphy images of the patient. Mildly increased flow (a, arrow) and pool (b and c, arrow) activity is seen in the region of right lower femur. On delayed image focal tracer uptake is seen in the lower shaft of right femur (d and e, arrow). Also noted was local recurrence in right proximal femur (d and e, broken arrow). No other site of skeletal metastasis was seen. To characterize the lower femoral lesion single photon emission tomography/computed tomography (SPECT/CT) was performed. CT (f-h) and SPECT/CT (i-k) images showed a sharply demarcated, asymmetrical, multiloculated, cortical based radiolucent lesion with sclerotic margins, located in the right femoral metaphysis and showing increased radiotracer uptake (arrow). These fi ndings were classical for a non-ossifying fibroma. Furthermore, there is increased tracer uptake in the right lower limb joints proximal and distal to the femoral lesion-suggestive of associated sympathetic hyperactivity (d and e)

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   Discussion Top


NOF are benign lesions, usually arising from the metaphysis of long bones of lower extremity. [1] They can be seen in about 35% of children and young adults. [2] NOFs are usually asymptomatic and incidentally diagnosed on routine radiographs. [3] These are considered "no touch lesions" and treatment is observation. [4] On three-phase bone scintigraphy appearance of NOF is variable and could either have hyperemia or increased uptake on delayed phase. [5],[6] Due to this non-specific appearance on bone scintigraphy, planar imaging appearance of NOF can be confused with metastasis or infection. SPECT/CT has been shown to be useful for correctly characterizing various bone lesions seen on bone scintigraphy. [7],[8] As the CT appearance is pathognomonic of NOF [9] SPECT/CT might prove to be very useful for this purpose in NOF. In the present case addition of SPECT/CT was able to correctly identify the lower femoral lesion as NOF thereby avoiding unnecessary biopsy, as well as it ruled out bone metastasis. Majority of NOF do not require any active treatment and can be left alone. Surgical excision is indicated only for lesions with concomitant or high risk of pathological fracture and very rarely for NOF producing phosphaturic peptides, thereby causing tumor induced osteomalacia. [4]

 
   References Top

1.Hudson TM, Stiles RG, Monson DK. Fibrous lesions of bone. Radiol Clin North Am 1993;31:279-97.  Back to cited text no. 1
    
2.Ritschl P, Karnel F, Hajek P. Fibrous metaphyseal defects - Determination of their origin and natural history using a radiomorphological study. Skeletal Radiol 1988;17:8-15.  Back to cited text no. 2
    
3.Friedland JA, Reinus WR, Fisher AJ, Wilson AJ. Quantitative analysis of the plain radiographic appearance of nonossifying fibroma. Invest Radiol 1995;30:474-9.  Back to cited text no. 3
    
4.Kumar R, Madewell JE, Lindell MM, Swischuk LE. Fibrous lesions of bones. Radiographics 1990;10:237-56.  Back to cited text no. 4
    
5.Hod N, Levi Y, Fire G, Cohen I, Ayash D, Somekh M, et al. Scintigraphic characteristics of non-ossifying fibroma in military recruits undergoing bone scintigraphy for suspected stress fractures and lower limb pains. Nucl Med Commun 2007;28:25-33.  Back to cited text no. 5
    
6.Greyson ND, Pang S. The variable bone scan appearances of nonosteogenic fibroma of bone. Clin Nucl Med 1981;6:242-5.  Back to cited text no. 6
[PUBMED]    
7.Sharma P, Singh H, Kumar R, Bal C, Thulkar S, Seenu V, et al. Bone scintigraphy in breast cancer: Added value of hybrid SPECT-CT and its impact on patient management. Nucl Med Commun 2012;33:139-47.  Back to cited text no. 7
    
8.Sharma P, Dhull VS, Reddy RM, Bal C, Thulkar S, Malhotra A, et al. Hybrid SPECT-CT for characterizing isolated vertebral lesions observed by bone scintigraphy: Comparison with planar scintigraphy, SPECT, and CT. Diagn Interv Radiol 2013;19:33-40.  Back to cited text no. 8
    
9.Clyde AH. Benign cystic lesions. In: Clyde AH, editor. Fundamentals of Skeletal Radiology. 2 nd ed. Philadelphia: WB Saunders; 1989. p. 18-9.  Back to cited text no. 9
    


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