Spindle cell lipoma in an intramuscular lipoma

Abstract

Intramuscular lipoma (IML) is a relatively common variant of lipomas. The most important sites for IML are the large muscles of the extremities. Spindle cell lipoma (SCL) is a rare and distinct variant of lipoma. Most SCL arise in the neck, shoulders or back. It has also been described in unusual sites, such as the oral cavity, larynx, bronchus, breast, orbit and extremities. However, localization of a SCL in an IML has not been described yet. Thus, we present the first SCL located in an IML, which was localized underneath the fascia and embedded within the left sartorius muscle of a 55-year-old man. Microscopically, the SCL component of the tumor was sharply circumscribed by a fibrous capsule and clearly separated from the IML in which it was localized. The collagen-forming spindle cells of the SCL showed neither atypia nor pleomorphism. These cells stained positive for CD34, while the mature fat tissue component of the SCL was positive for S-100 protein and negative for CD34. Spindle cells were negative for S-100 protein. Vimentin stained both components of the SCL, as well as the striated muscle fibers and mature fat tissue of the IML. In conclusion, careful morphological observation along with immunohistochemistry for CD34 and S-100 protein are essential to differentiate this rare tumor from lesions that enter the differential diagnosis.

Co-existence of intramuscular spindle cell lipoma with an intramuscular ordinary lipoma:report of a case

“…Intramuscular development of this tumor is noted mainly in the same regions that subcutaneous spindle cell lipomas occur. Of the 14 already published cases 8 were located in the shoulder, neck and upper back area as in our case [3,4,6,9,11,[13][14][15], 2 were located in the head [8,12], 2 in the arm [2,5] and 2 in the thigh [7,10]. The concurrent intramuscular existence of a spindle cell lipoma and of an ordinary lipoma is very rare and to our knowledge only four cases have been described in the literature [7,[13][14][15].…”

“…It is a relatively rare variant (1.5% of all adipocytic neoplasms), and a histologically distinct lesion characterized by the replacement of mature fat from collagen forming spindle cells and eosinophilic collagen bundles with a benign clinical course [2,3]. Intramuscular development of these tumors is very rare and to our knowledge only 14 cases have been reported so far [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Coexistence of intramuscular mature lipoma and spindle cell lipoma has also very rarely been reported.…”

Intramuscular spindle cell lipoma/pleomorphic lipoma unusual site fore arm

“…However, few unusual sites have also been reported such as the tonsillar fossa, orbit, and tongue amongst which intramuscular compartment forms a minority. 7,8 Our case is also a 58-year-old male patient. The lesion presented as a painless mobile soft swelling, which can be mistaken for a lipoma.…”

Letter to the editor. Re: Co-existence of intramuscular spindle cell lipoma with an intramuscular ordinary lipoma. Report of a case

“…Third, the co-existence of spindle cell lipoma and an ordinary lipoma has been documented [2][3][4][5]. The authors state that the concurrent intramuscular existence of spindle cell lipoma and of an ordinary lipoma is very rare.…”