Soft tissue tumors - Leiomyoma-Classic

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Soft tissue tumors

Smooth muscle

Leiomyoma-Classic

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 23 February 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

Leiomyoma: see also bizarre, cutaneous, epithelioid, genital, leiomyoma of deep soft tissue

Definition
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● Bland smooth muscle tumor without mitotic figures (eMedicine)

Terminology
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● Not a WHO diagnosis (cutaneous and pilar tumors are described in the Skin volume)
● Some tumors previously considered to be leiomyomas are actually GI stromal (GIST) tumors
● See also Colon-tumor, Esophagus, Uterus chapters

Epidemiology
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● Skin and subcutis; also deep soft tissue, uterus (most common neoplasm in women)
● Patients with multiple cutaneous leiomyomas may have autosomal dominant disorder (described under Cutaneous leiomyoma)

Case reports
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● 34 year old man with sickle cell thalassemia and ossified leiomyoma (J Cutan Pathol 2005;32:696)
● 59 year old woman with finger lesion (Chang Gung Med J 2004;27:134)

Gross images
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Myxoid subcutaneous tumor

Micro description
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● Bundles or fascicles of spindled cells with eosinophilic and possibly fibrillary cytoplasm
● Nuclei are blunt ended and elongated with fine chromatin, indistinct nucleolus and variable cytoplasmic vacuole at one end
● Minimal atypia
● Few mitotic figures
● No coagulative tumor necrosis

Micro images
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Bundles of elongate cells with eosinophilic cytoplasm and oblong nuclei

Oblong nuclei have rounded ends

Calcified leiomyoma

Positive stains
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● Desmin, alpha smooth muscle actin
● h-caldesmon, calponin, muscle specific actin, myosin
● ER and PR for uterine tumors

Negative stains
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● CD117, CD34, S100; low Ki-67 (<5%)

Differential diagnosis
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● Angiomyolipoma: usually prominent vascular and lipomatous component
● Leiomyosarcoma: more cellular, infiltrative, pleomorphic; mitotic activity and coagulative tumor cell necrosis

End of Soft tissue tumors > Smooth muscle > Leiomyoma-Classic

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