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Soft tissue tumors

Smooth muscle

Smooth muscle tumors - general

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

Micro description

● Tumor cells resemble smooth muscle with easily visible, often fibrillar and eosinophilic cytoplasm, usually in long bundles or fascicles
● Nucleus is long, oval and round at both ends, often with cytoplasmic vacuole at one end, nucleoli are indistinct
● Minimal collagen present between smooth muscle cells
● Smooth muscle cells may resemble myofibroblasts with less cytoplasm, thinner nuclei, denser chromatin
● Note: smooth muscle tumors of skin, vulva/vagina, scrotum, nipple and other locations are described in these chapters

Micro images

Smooth muscle



Smooth muscle composite

Positive stains

● Trichrome stains smooth muscle cytoplasm red and collagen blue or green
● Actin, desmin and calponin stain smooth muscle, but are non-specific because they also stain myofibroblasts
● Smooth muscle myosin and h-caldesmon are more specific for smooth muscle versus myofibroblasts (Am J Dermatopathol 2006;28:105)

End of Soft tissue tumors > Smooth muscle > Smooth muscle tumors - general

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