Soft tissue tumors - Pleomorphic leiomyosarcoma

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Soft tissue tumors

Smooth muscle

Pleomorphic 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, epithelioid, myxoid, rhabdoid features

Definition
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● Pleomorphic areas should be at least 2/3 of tumor

Epidemiology
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● 10% of all leiomyosarcomas
● Mean age 58 years, range 31-89 years

Clinical features
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● Usually extremities, also retroperitoneum/abdominal cavity, chest/abdominal wall, occasionally scalp
● May be more aggressive than ordinary leiomyosarcoma, as 65% die of disease

Case reports
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● 56 year old woman with pancreatic mass (J Int Med Res 2011;39:1555)
● 57 year old man with a mass in upper arm (Acta Cytol 2010;54:1013)
● 59 year old woman with adrenal tumor (Endocr Pathol 2005;16:75)
● 63 year old man with adrenal tumor (Arch Pathol Lab Med 2003;127:e32)
● 65 year old man with beta hcG producing retroperitoneal tumor (Sarcoma 2000;4:179)

Micro description
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● Focally fascicular with smooth muscle tumor cells
● Pleomorphic areas mimic MFH-pleomorphic
● Storiform pattern common
● Stromal hyalinization, chronic inflammatory infiltrate
● Usually high grade
● Occasionally rhabdoid features

Micro images
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Various images

Resembles MFH”

Abrupt transition from fascicular to pleomorphic areas

Positive stains
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● At least one smooth muscle marker (desmin, muscle-specific actin or alpha-smooth muscle actin) in the leiomyosarcomatous fascicular areas
● Also positive for collagen type IV around the individual tumor cells (Oncol Rep 1999;6:533)

Differential diagnosis
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● Atypical fibroxanthoma: superficial skin lesion with no necrosis, no vascular invasion, no infiltrative margins
● MFH-pleomorphic: negative for smooth muscle markers (i.e. no evidence of specific differentiation other than myofibroblasts / fibroblasts, Oncol Rep 1999;6:533, Am J Surg Pathol 2001;25:1030)
● Myofibrosarcoma: low grade tumor overall, may have numerous thin walled capillaries, no prominent inflammation

End of Soft tissue tumors > Smooth muscle > Pleomorphic leiomyosarcoma

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