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Soft tissue tumors

Smooth muscle


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 17 February 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.


● Benign, painful, subcutaneous or deep dermal tumor of smooth muscle and vessels
● Part of morphologic spectrum with myopericytoma (Hum Pathol 2007;38:645) and myofibroma
● Arises from smooth muscle of blood vessels without elastic fibers


● Also called angiomyoma, vascular leiomyoma
● Do NOT diagnose as “superficial angiomyolipoma” even if it contains some fat


● Relatively common, usually females, ages 30-60 years

Clinical features

● Solitary, slow growing nodule
● Often in soft tissue of lower limbs, but tumors in males are more common in upper extremity, head and neck (Laryngoscope 2004;114:661)
● Pain in 60% (Int J Clin Pract 2004;58:587), due to stretching of nerves in tumor or capsule or release of mediators from mast cells; pain may be exacerbated by wind, cold, pressure, menses
● Other painful nodules are glomus tumor, traumatic neuroma, eccrine spiradenoma and angiolipoma

Case reports

● 38 year old man with auricular tumor (Turk Patoloji Derg 2011;27:268)
● 51 year old man with nasal turbinate mass (Case of the Week #138)
● 57 year old man with recurrent oral tumor (Contemp Clin Dent 2011;2:102)
● 58 year old woman with small intestinal tumor (World J Surg Oncol 2007;5:129)
● 61 year old woman with thigh tumor for 10 years and coexisting epithelioid granuloma (Case Rep Dermatol 2011;3:170)
● 62 year old woman with nasal septum tumor (Braz J Otorhinolaryngol 2010;76:675)
● 66 year old woman with posterior mediastinal tumor (Yonsei Med J 2008;49:666)

Treatment and prognosis

● Simple excision; does not recur

Gross description

● Firm, sharply circumscribed gray-white-brown nodules
● Usually 2 cm or less

Gross / clinical images

Well dermacated tumors (left: small intestinal, right: posterior mediastinum)

Retromolar growth

Thigh nodule

Micro description

● Well circumscribed fascicles of mature smooth muscle cells surrounding vascular lumina, lined by normal appearing endothelium but with no elastic lamina present
● Subtypes are solid (closely compacted smooth muscle bundles), venous (vessels have thick muscular walls that merge with smooth muscle bundles) and cavernous (dilated vascular channels with minimal smooth muscle that merges with smooth muscle bundles), but subtypes have no clinical significance (Cancer 1984;54:126)
● Venous type is most common in head and neck, usually males
● Solid type is most common in lower extremeties, usually females
● May have foci of cartilaginous or adipose metaplasia
● May have bizarre degenerative type cells similar to symplastic leiomyoma of uterus
● Rarely prominent calcification in acral sites (J Am Acad Dermatol 2008;59:1000)
● Rarely epithelioid cells (Am J Dermatopathol 1998;20:213) or epithelioid granulomas (Case Rep Dermatol 2011;3:170)
● No hemorrhage, no necrosis, no mitotic activity, no vasculitis, no fibromuscular dysplasia

Micro images

Smooth muscle and vessels, often thick walled

Smooth muscle in vessel walls merge with smooth muscle of lesion

Closely compacted eosinophilic smooth muscle cells merge with blood vessels

Mediastinal tumor

Nasal cavity (left to right): submucosal tumor composed of abundant thick-walled blood vessels blending with proliferative smooth muscle tissue; focal fatty metaplasia; smooth muscle actin+

Nasal turbinate: H&E (3) and actin (2)

Oral cavity: retromolar mass

Skin tumor

Skin tumor-ear

Skin-thigh tumor

Small intestinal tumor

Cytology description

● Moderate or sparse cellularity
● Usually uniform spindle cells mixed with smooth muscle cells and fragments of collagenous tissue in varying proportions
● Occasional macrophages, fat cells, ganglion-like cells (Diagn Cytopathol 2002;27:161)

Positive stains

● Alpha smooth muscle actin, desmin, myosin, trichrome, HHF35, calponin, h-caldesmon
● Also vimentin, type IV collagen, S100 in small nerve fibers
● Variable PR in nasal cavity cases (Acta Otolaryngol 2002;122:408, Chin Med J (Engl) 2007;120:350)

Negative stains

● HMB45, ER

Differential diagnosis

● Angiomyolipoma - prominent adipose tissue component, HMB45+
Leiomyoma with bizarre nuclei: no prominent vascular component

End of Soft tissue tumors > Smooth muscle > Angioleiomyoma

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