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Intramuscular lipoma of the pectoralis major muscle. U Gopal, MH Patel, MK Wadhwa, Correspondence Address: PMID: 12571401
Keywords: Aged, Case Report, Female, Human, Muscle Neoplasms, diagnosis,radiography,surgery,Pectoralis Muscles, Tomography, X-Ray Computed,
Sir, A 70-year-old post-menopausal woman presented with a 7-years history of a slowly increasing painless swelling in the right breast with pain and discomfort over the right shoulder for past 6-months. Local examination showed an enlarged right breast having a 16x8 cm size, hard, non-tender lump in the upper half with normal overlying skin, nipple and areola. The mammography appearance was suggestive of a benign sub-mammary lipoma. On sonography, the mass was homogenously echogenic with well defined margins. CT scan showed a big solitary, homogenous fat density mass (-100 HU) in the right sub-mammary region with intervening septations and bisecting the pectoralis major muscle. No haemorrhage, necrosis or calcification was noted. Except anterior displacement of the right breast, both breasts and axillae were normal. No post-contrast enhancement of the lesion was noted. These findings were consistent with a diagnosis of lipoma of the right pectoralis major muscle. Complete excision was performed under general anaesthesia. A well circumscribed, round to oval multi-lobular, yellowish brown mass measuring 16x 15x5.5 cm was removed. The cut surface was solid, firm, yellowish, shiny and without haemorrhage or calcifications. Microscopic examination showed mature adipose tissue. Surgical margins of resection were negative for the tumour. Lipomas are one of the most frequently encountered benign mesenchymal tumours composed of mature fat tissue, commonly found in the superficial subcutaneous tissues of the extremities and trunk. A lipoma may occasionally be found within the muscle (i.e. intramuscular or infiltrating lipoma) or between the muscles (i.e. intermuscular lipoma). Intramuscular lipomas are extremely rare.[1],[2] In most reported cases the tumours involved the extremities and trunk[1],[3] or rarely involved different muscles in the head and neck region.[4],[5] Report on an intramuscular lipoma involving pectoralis major muscle could not be found in the literature. Most lipomas are subcutaneous and require no imaging evaluation. When deep/ large/ unusual in location, radiography, CT/ MRI scan can identify and localise these tumours. Radiolucency and poor vascularisation are characteristics of a lipoma on plain radiography. A lipoma appears as a sharply defined marginated, homogenous fat density mass on CT scan. In our case, the mammographic findings were suggestive of a sub-mammary lipoma and CT scan findings led to radiological diagnosis of an intramuscular lipoma of the pectoralis major muscle, prior to the excision and histopathological confirmation of the diagnosis. The treatment is complete surgical excision. Incomplete excision may lead to recurrence. Dionne and Seemayer reported 62.5% recurrence rate.[2] In our patient, the tumour was completely excised and there is no evidence of recurrence after 5 years. In conclusion, an intramuscular lipoma of the pectoralis major muscle is exceptionally rare and practically never enters into the clinical differential diagnosis of the benign or malignant tumours in this location. However radiologically, it can be diagnosed prior to histopathological confirmation.
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