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 Table of Contents  
CASE REPORT
Year : 2022  |  Volume : 2  |  Issue : 4  |  Page : 971-973

Orbital intramuscular lipoma with bone erosion: A case report and review of literature


1 Department of Ophthalmology, Queen Sirikit National Institute of Child Health, Bangkok, Thailand
2 Department of Surgery, Division of Neurosurgery, Queen Sirikit National Institute of Child Health, Bangkok, Thailand

Date of Submission25-Jan-2022
Date of Acceptance20-Jul-2022
Date of Web Publication11-Oct-2022

Correspondence Address:
Dr. Nutsuchar Wangtiraumnuay
Department of Ophthalmology, Pediatrics Ophthalmologist and Ocular Genetics, Queen Sirikit National Institute of Child Health, Bangkok
Thailand
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijo.IJO_248_22

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  Abstract 


This report highlights a rare case of a benign orbital intramuscular lipoma mimicking a malignant tumor with unusual sphenoid wing destruction. A 2-year-old female patient presented with proptosis of the left eye, left temporal fullness, and motility disturbance during abduction. Brain and orbital computed tomography revealed an inhomogeneous enhancing density partially circumscribed mass in the left extraconal space (36.6 × 34.4 × 34.2 mm) with bone erosion of the greater wing of the left sphenoid bone. The clinical and radiologic findings suggested rhabdomyosarcoma. Histopathology revealed diffuse infiltration of mature adipocytes in the striated muscle. An intramuscular lipoma, a rare subtype of benign lipoma, can mimic malignant orbital tumors due to adjacent bone erosion.

Keywords: Bone erosion, intramuscular lipoma, orbital mass


How to cite this article:
Lueangaram S, Pittayapongpat R, Kittisangvara L, Wangtiraumnuay N. Orbital intramuscular lipoma with bone erosion: A case report and review of literature. Indian J Ophthalmol Case Rep 2022;2:971-3

How to cite this URL:
Lueangaram S, Pittayapongpat R, Kittisangvara L, Wangtiraumnuay N. Orbital intramuscular lipoma with bone erosion: A case report and review of literature. Indian J Ophthalmol Case Rep [serial online] 2022 [cited 2022 Nov 27];2:971-3. Available from: https://www.ijoreports.in/text.asp?2022/2/4/971/358163



Lipomas are the most common mesenchymal tumors and consist of mature adipocytes. They typically occur in the subcutaneous tissue of the trunk and extremities and are called subcutaneous lipomas. There are many subtypes of lipoma, such as angiolipoma, chondroid lipoma, lipoblastoma, pleomorphic lipoma/spindle cell lipoma, and intramuscular lipoma. Intramuscular lipomas have been studied extensively and categorized in the same group as other deep-seated and superficial lipomatous lesions. This type of tumor is uncommon. It has been reported in only 1.8% of all adipose tissue tumors and less than 1% of all lipomas.[1],[2] Coexistence with other intramuscular lipomas, such as spindle cell lipoma, periosteal lipoma, and well-differentiated liposarcoma, has been reported.[3],[4],[5] An intramuscular lipoma is frequently present in large muscles such as those in the trunk and extremities but is rare in the head and neck regions. Two cases of intramuscular lipoma on the eyelid have been reported.[6],[7] In addition, two patients presented with tumors involving the extraocular muscle (superior rectus muscle and superior oblique muscle).[8],[9] In all four of these cases, the tumors presented with neither adjacent bone invasion nor bone erosion.

We report a case of an intramuscular lipoma in the orbit with proptosis and temporal fullness, mimicking an orbital malignancy due to associated bone erosion.


  Case Report Top


A 2-year-old girl presented with the gradual enlargement of a temporal mass and mild proptosis in her left eye for 6 months. She turned her head when looking to the left. The patient did not complain of ocular pain, and her medical history was unremarkable.

Upon examination, her fixation was centrally steady and maintained. Slit-lamp and fundoscopic examinations were unremarkable. Ocular motility examination demonstrated mild limitation of abduction of the left eye. Mild proptosis was observed in the left eye. MRD1 was + 4 mm for the right eyelid and +2 mm for the left eyelid.

The orbital computed tomography (CT) scans revealed a left inhomogeneous density, enhancing a partially encapsulated mass in the left extraconal space and measuring 36.6 × 34.4 × 34.2 mm, without calcification and no definite fat component. The radiodensity of the mass was 33.26–73.46 Hounsfield units (HU). Direct tumor invasion into the left lateral rectus muscle and inferotemporal part of the temporalis muscle was detected. Additionally, bone erosion on the greater wing of the left sphenoid bone without a periosteal reaction was observed in the CT orbit with contrast [Figure 1]. Preoperative orbital magnetic resonance imaging (MRI) was not performed.
Figure 1: Orbital CT scan with contrast media demonstrated inhomogeneous density enhancing rather circumscribed mass at left extraconal space size 36.6 × 34.4 × 34.2 mm without calcification. (a) Axial section with contrast media. (b) Coronal section with contrast media. (c) Coronal bone window

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Based on clinical and radiologic findings, rhabdomyosarcoma was the most likely diagnosis. The patient underwent a lateral orbitotomy with tumor removal. A light-brown rubbery mass was found intraoperatively. Fatty-like tissue had replaced the normal tissue in the area, including the area of bone destruction. An excisional biopsy was performed, and the adjacent bone and dura were not exposed or excised. The histopathology report described a diffuse infiltrate of mature adipocytes in striated muscle, neither lipoblasts nor nuclear atypia, with the diagnosis of an intramuscular lipoma [Figure 2]. All clinical features resolved, and gross total tumor removal was confirmed on postoperative MRI [Figure 3] and [Figure 4]. Postoperative CT was not performed. The limitations of the extraocular movement were resolved. During a 4-year follow-up, the patient was clinically stable without recurrence.
Figure 2: Histopathology of the intramuscular lipoma. (a) H and E stain × 5. (b) H and E stain × 10. (c) H and E stain × 20. The section reveal a diffuse infiltrate of mature lipocytes in the striated muscle. Neither lipoblasts nor atypical nuclei are seen

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Figure 3: Clinical appearance. (a) The patient with mild proptosis and temporal fullness of the left eye. (b) The patient after lateral orbitotomy and tumor removal for 3 months

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Figure 4: MRI of the brain. (a) Axial T1W and T2W showed decrease size of mass hypointensity T1W and mild hyperintensity T2W lesion at left greater and lesser wings of the sphenoid bone adjacent to the squamous part of the left temporal bone. (b) Coronal T1W and T2W hyperintensity change of left temporalis muscle and no definite bone erosion

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  Discussion Top


Lipomas (fat tumors) are the most common type of soft-tissue mesenchymal tumors. They are most commonly found on the trunk and extremities, and 20–25% occur in the head and neck region.[10] Less common lipomas may occur in deep locations such as the mediastinum, periosteum, and intestinal walls. Intramuscular lipomas are rarer than typical superficial lipomas. On CT, intramuscular lipomas are usually hypodense, well-defined lesions situated in the muscle tissue with Hounsfield values in the negative range.[11] The mass is usually ovoid or fusiform and has the same density as other soft tissues.[12] On MRI, the intramuscular lipoma fatty tissue is hyperintense in both T1W and T2W images. Fat-suppressed sequences demonstrate signal suppression similar to that of normal fat. Intramuscular lipomas can be homogeneous or heterogeneous because of the intermingled muscle fibers and tumor tissue. Interdigitations with skeletal muscle showing a characteristic striated appearance are pathognomonic for an intramuscular lipoma and have not been described in other lipomatous tumors. Based on the available literature, intramuscular lipomas do not produce adjacent bone lesions. Among all four described orbital intramuscular lipomas, two were found in the extraocular muscles and two in the anterior orbit. They showed typical imaging findings of lipomas with a normal adjacent bone. Conservative management is the mainstay of treatment. Symptomatic intramuscular lipomas require intralesional steroid injection or surgical removal.[6]

Our patient presented with a typical intramuscular lipoma with an inhomogeneous hypo- and iso-dense ovoid mass with enhancement with contrast media from the lateral rectus invasion into the infratemporal temporalis muscle. The radiodensity of the mass was 33.26–73.46 HU, which is compatible with the radiodensity of muscles or soft tissues. In contrast, our case showed a questionable presentation of sphenoid bone destruction. Some benign orbital tumors in children may present with bone destruction, such as eosinophilic granulomas, leiomyomas, and orbital intraosseous hemangiomas.[13] Histologically, intramuscular lipomas can be divided into infiltrative, well-circumscribed, and mixed types (with areas of infiltrative margins and well-circumscribed or encapsulated areas). The histological features of infiltrative intramuscular lipomas are distinct. They have a relatively uniform appearance characterized by mature adipocytes of uniform size and shape, which irregularly infiltrate muscle fibers and completely replace muscle bundles.[14]

An intramuscular lipoma, a subtype of lipoma rarely found in the orbit, behaves as an ovoid-shaped mass, causing ocular motility disorders and proptosis. Imaging studies showed an inhomogeneous mass with an internal signal or density similar to that of muscle fiber tissue.


  Conclusion Top


Our case exemplifies an intramuscular lipoma, a rare subtype of benign lipoma that mimicked a malignant orbital tumor because of adjacent bone erosion.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Fletcher CD, Martin-Bates E. Intramuscular and intermuscular lipoma: Neglected diagnoses. Histopathology 1988;12:275-87.  Back to cited text no. 1
    
2.
Lee JH, Do HD, Lee JC. Well-circumscribed type of intramuscular lipoma in the chest wall. J Cardiothorac Surg 2013;8:181. doi: 10.1186/1749-8090-8-181.  Back to cited text no. 2
    
3.
Matsumoto K, Hukuda S, Ishizawa M, Egawa M, Okabe H. Liposarcoma associated with multiple intramuscular lipomas. A case report. Clin Orthop Relat Res 2000;373:202-7.  Back to cited text no. 3
    
4.
Usta U, Türkmen E, Mizrak B, Yildiz D, Güzel Z. Spindle cell lipoma in an intramuscular lipoma. Pathol Int 2004;54:734-9.  Back to cited text no. 4
    
5.
Laliotis A, Bree E, Vasilaki S, Papadakis M, Melissas J. Co-existence of intramuscular spindle cell lipoma with an intramuscular ordinary lipoma: Report of a case. Pol J Pathol 2013;64:224-7.  Back to cited text no. 5
    
6.
McTighe S, Chernev I. Intramuscular lipoma: A review of the literature. Orthop Rev (Pavia) 2014;6:5618. doi: 10.4081/or. 2014.5618.  Back to cited text no. 6
    
7.
Buller A, O'Donnell A, Bonshek RE, Leatherbarrow B. Intramuscular lipoma of the eyelid: A case report. Eye (Lond) 2004;18:743-5.  Back to cited text no. 7
    
8.
Vahdani K, Mcveigh K, Ford R. Superior rectus intramuscular lipoma. Ophthalmic Plast Reconstr Surg 2017;33:396-7.  Back to cited text no. 8
    
9.
Dutton JJ, Wright JD Jr. Intramuscular lipoma of the superior oblique muscle. Orbit 2006;25:227-33.  Back to cited text no. 9
    
10.
Kransdorf MJ, Bancroft LW, Peterson JJ, Murphey MD, Foster WC, Temple HT. Imaging of fatty tumors: Distinction of lipoma and well-differentiated liposarcoma. Radiology 2002;224:99-104.  Back to cited text no. 10
    
11.
Pant R, Poh AC, Hwang SG. An unusual case of an intramuscular breast mass. Ann Acad Med Singap 2005;34:275-6.  Back to cited text no. 11
    
12.
Nishida J, Morita T, Ogose A, Okada K, Kakizaki H, Tajino T, et al. Imaging characteristics of deep-seated lipomatous tumors: Intramuscular lipoma, intermuscular lipoma, and lipoma-like liposarcoma. J Orthop Sci 2007;12:533-41.  Back to cited text no. 12
    
13.
Yan J, Zhou S, Li Y. Benign orbital tumors with bone destruction in children. PLoS One 2012;7:e32111.  Back to cited text no. 13
    
14.
Kindblom LG, Angervall L, Stener B, Wickbom I. Intermuscular and intramuscular lipomas and hibernomas: A clinical, roentgenologic, histologic, and prognostic study of 46 cases. Cancer 1974;33:754-62.  Back to cited text no. 14
    


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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]



 

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