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Soft tissue tumors

Smooth muscle

Epithelioid leiomyosarcoma


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

Leiomyosarcoma: see also general, cutaneous, myxoid, pleomorphic, rhabdoid features

General
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● Usually in uterus; rare in bone, soft tissue, skin or subcutis (Am J Surg Pathol 1994;18:232)
● In stomach is called leiomyoblastoma

Case reports
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● Infant with intraabdominal mass (Mod Pathol 2000;13:1156)
● 6 year old girl with mandibular tumor (Klin Padiatr 2005;217:291)
● 18 year old man with scrotal mass (Urol J 2004;1:215)
● 56 year old man with tumor of gastrocolic ligament (Acta Chir Belg 2003;103:105)
● 71 year old man with rectal tumor with osteoclast-like giant cells (Arch Pathol Lab Med 2000;124:438)
● 78 year old man with thigh tumor (Arch Pathol Lab Med 2002;126:468)

MRI images
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18 month old girl with intraabdominal mass

Gross images
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71 year old man with rectal tumor

Micro description
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● Round/polygonal cells with eosinophilic and vacuolated cytoplasm, vesicular nuclei
● Arranged in sheets with focal spindle cells

Micro images
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Various images


Bladder tumor: H&E and actin

Rectal tumor with osteoclast-like giant cells

Cytology description
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● Mononuclear, binucleated or multinucleated cells with eccentric nuclei and dense to vacuolar cytoplasm (Acta Cytol 1997;41:1801)
● Also highly cellular smears with many single polygonal cells having eccentric, malignant nuclei and a characteristic clear quality to the cytoplasm in Pap-stained material (Diagn Cytopathol 1994;11:321)

Positive stains
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● Alpha-smooth muscle actin, alpha-sarcomeric actin, vimentin
● Also CD99/MIC2
● Reticulin stain outlines individual tumor cells

Negative stains
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● CAM 5.2, EMA, CD34, CD45; usually desmin
● Factor VIII, glial fibrillary acidic protein, HMB45, S100, CD1a (Ann Diagn Pathol 2008;12:401)

Electron microscopy description
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● Abundant actin-type filaments in cytoplasm of some cells, glycogen

Electron microscopy images
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Intermediate filaments, thin filaments with subplasmalemmal dense bodies and glycogen

Differential diagnosis
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Epithelioid sarcoma
Melanoma: S100+, HMB45+
Metastatic carcinoma: clinical history, keratin+, no areas of classic leiomyosarcoma
Metastatic uterine tumor: clinical history

End of Soft tissue tumors > Smooth muscle > Epithelioid leiomyosarcoma


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