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CASE REPORT

Intraosseous Lipoma Of The Capitate: A Case Report

Andrew P H*,Patricia L M**,James H F**

*F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd, Bethesda, MD   20814
** Department of Orthopedics, National Naval Medical Center, 8901 Wisconsin Ave, Bethesda, MD  20889
 

Address for Correspondence:  

Andrew P. Hurvitz, BS, ENS, MC, USN
F. Edward Hebert School of Medicine
Uniformed Services University of the Health Sciences
4301 Jones Bridge Rd, Bethesda,
MD   20814
Email: s9ahurvitz@usuhs.mil
Phone: (323) 804-6300


 

Abstract:

Intraosseous lipomas are rare, benign tumors of the bone.  This report reviews the radiographic and histopathologic findings consistent with this type of lesion

J.Orthopaedics 2008;5(4)e2

Keywords:

carpal bones; capitate; intraosseous lipoma


Introduction:

Lipomas are frequently discovered in the soft tissues.  Intraosseous lipomas, however, are considerably less common.  Despite the normal existence of fat in the marrow space, an intraosseous lipoma is a focal growth of mature adipocytes within the medullary cavity of bone.  There is a slight male predominance and diagnosis occurs throughout a wide age range with a peak incidence in the forties.1,2,3  The first case was reported in 1910 by Wehrsig4, describing an intraosseous lipoma in the proximal fibula of a 5 year old girl.  Intraosseous lipomas occur primarily in the metaphyses of bone, most commonly involving the long bones of the lower extremity.1,2,3  We present a unique case of an intraosseous lipoma discovered in the capitate of a 38 year old man.  A search of the English and Foreign literature from 1910 to present revealed 28 cases of intraosseous lipoma occurring in the upper extremity, only one of which was described in a carpal bone.  That particular case, which also occurred in the capitate, was reported by Baron in 1987.5 

Case Report:
 

In May of 2006, a 38 year old right-hand dominant male presented to a Family Practice clinic approximately 3 weeks after falling on his outstretched left hand.  The patient reported mild pain and swelling of the left wrist with a clicking sensation upon movement.

            On physical exam, he was noted to have tenderness to palpation at the ulnar aspect of the left wrist, with restricted wrist motion and pain with full flexion and extension.  There was no visual deformity or palpable mass of the left wrist.  Light sensation was intact throughout both upper extremities, and the patient had palpable, symmetric pulses bilaterally.

Initial radiographic examination by plain films revealed a 9mm diameter lytic lesion in the proximal pole of the capitate, with a sclerotic, well-defined border proximally, but poorly defined distally (Fig 1).  The lesion was presumptively diagnosed as a capitate cyst and the patient was referred to a hand specialist for further evaluation and definitive treatment. 

 

Figure 1 : Anteroposterior radiograph of the left wrist demonstrate a lytic lesion in the proximal pole of the capitate, with a sclerotic, well-defined border proximally, but poorly defined distally.

            Reexamination 1 month later confirmed earlier findings; the patient was tender over the ulnar aspect of the left wrist, but denied any paresthesias.  Subsequent MRI revealed a well-corticated, benign-appearing lesion with thin, sclerotic margins.  Axial T1 weighted images demonstrated a circular, hyperintense lesion within the capitate with a focal area of hypointensity ulnarly, isointense to fluid (Fig 2).  Axial T2 fat suppressed images showed suppression of the signal within the lesion, indicating the presence of fat.  There was also a focal area of intensity ulnarly that was consistent with cystic degeneration (Fig 3).  A diagnosis of intraosseous lipoma was made and, after thorough discussion of the treatment options, the patient elected for surgical excision of the lesion.

 

 

 

 

 

 

 

 

 

 

 

Figure 2 : Axial T1 weighted image demonstrates a circular, hyperintense lesion within the capitate with a focal area of hypointensity ulnarly, isointense to fluid. 

Figure 3 : Axial T2 fat suppressed images shows suppression of the signal within the lesion, indicating the presence of fat.  There is also a focal area of intensity ulnarly, consistent with cystic degeneration. 

 

Intraoperatively, the capitate was exposed and the lesion was removed under direct vision.  The gross findings were consistent with intraosseous lipoma, with a small focus of cystic degeneration as seen on the MRI.  The histopathology from this case is not available for publication, however, a representative case in the calcaneus reveals the typical features of an intraosseous lipoma, demonstrating a proliferation of mature-appearing adipocytes interposed with an area of ischemic ossification (Fig 4).

Figure 4 :Photomicrograph of a representative intraosseous lipoma discovered in the calcaneus, displaying a   proliferation of viable, mature-appearing adipocytes with mild degenerative and fibrotic change and evidence of an irregular area of ischemic ossification toward the left of the image. Courtesy of Daniel Strum, MD; Armed Forces Institute of Pathology, Walter Reed, Washington DC
 

Discussion :

Intraosseous lipomas are rare, benign neoplasms of bone.  Their incidence has previously been reported as less than 0.1% of all bone tumors6,7,8, however, more recent studies have suggested this value is an underestimate.3,6,7  The reason for this undervaluation is likely attributed to the relatively asymptomatic nature of the lesion.  These lesions are most common in the metaphyses of long bones, particularly of the lower extremity.  A comprehensive search of the literature revealed 28 total cases occurring in the upper extremity, only one of which has been previously described in the capitate.5  

The largest study to date was performed by Milgram in 1988 on 61 cases of intraosseous lipomas.1  In this study, most lesions were discovered in the femur, tibia and fibula.  None of the lipomas were found in the hands or feet, with the exception of five cases in the calcaneus.  Milgram divided intraosseous lipomas into three groups based on their respective histology.  Stage 1 lesions consist of viable fat cells with cortical expansion; Stage 2 lesions are composed of fat cells with areas of necrosis and calcification; Stage 3 lesions are described as having necrosis, calcification, cyst formation, and reactive woven bone formation. 

Clinically, these neoplasms may present with localized discomfort or swelling.3,7  The majority of cases, however, tend to be asymptomatic and are discovered incidentally during radiographic work-up for unrelated musculoskeletal injuries and fractures.1,2,3  In this particular case, a cystic lesion was initially described on plain film and subsequently diagnosed as an intraosseous lipoma, as indicated by the characteristics of the lesion on MRI.   

Symptomatic patients may elect to have intraosseous lipomas excised with subsequent bone grafting1,2, however, surgical treatment is not a requirement.  Asymptomatic patients are encouraged to avoid surgical intervention as there is little reported risk of malignant change.1,2,6  The rate of recurrence for these lesions is very low and has, therefore, not been a factor in the surgical treatment of these lesions.1,2

While the occurrence of intraosseous lipoma is infrequent, it is important to consider this tumor in the differential diagnosis of cystic-appearing lesions of the carpal bones.  An MRI or CT should be performed to establish the diagnosis of intraosseous lipoma as both can accurately demonstrate the presence of fat within a lesion.2,3,6

 

Reference :

1.         Milgram JW. Intraosseous Lipomas. A clinicopathologic study of 66 cases. Clinical Orthopedics 1988; 231:277-301.

2.         Milgram JW.  Intraosseous lipomas: radiologic and pathologic manifestations. Radiology 1988;167:155-160.

3.         Murphey MD, Carroll JF, Flemming DJ, Pope TL, Gannon FH, Kransdorf MJ.  Musculoskeletal archives.  AFIP Archives.  Radiographics 2004;24:1433-1466.

4.         Wehrsig G. Lipom des Knochenmarks. Centralblatt fur allgemeine Pathologie und pathologische Anatomie 1910;21: 2437.

5.         Baron J, Scharizer E.  Tumors and tumor-like diseases of the carpal bones.  Handchirurgie, Mikrochirurgie, Plastische Chirurgie 1987; 19(4): 195-205.

6.         Propeck T, Bullard M, Lin J, Doi K, Martel W. Radiologic-Pathologic correlation of intraosseous lipomas. American  Journal of Roentology 2000;175:673-678.

7.         Chow L, Lee K. Intraosseous lipoma: a clinicopathologic study of nine cases.  American Journal of  Surgical Pathology 1992; 16(4):401-410.

8.         Nahles G, Schaeper F, Bier J, Klein M.  An intraosseous lipoma in the frontal bone - a case report.  International Journal of Oral and Maxillofacial Surgery 2004; 33(4):408-410.

9.         Plate A, Lee SJ, Steiner G, Posner MA.  Tumorlike Lesions and     Benign Tumors of the Hand and Wrist. Journal of American Academy of Orthopedic Surgery 2003;11:129-141.

 

This is a peer reviewed paper 

Please cite as : Andrew P H : Intraosseous Lipoma Of The Capitate: A Case Report

J.Orthopaedics 2008;5(4)e2

URL: http://www.jortho.org/2008/5/4/e2

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