Leiomyosarcoma

A leiomyosarcoma is a rare, malignant tumour displaying smooth muscle differentiation. Leiomyosarcomas comprise approximately 7% of all soft tissue sarcomas. The vast majority of these lesions occur in the uterus and gastrointestinal tract, and are rare in the skin.

In the skin, lesions are divided into the two subcategories of dermal and subcutaneous leiomyosarcomas due not only to their difference in location, but also due to differences in their likely site of origin and prognosis. 

This chapter is set out as follows:   

Dermal leiomyosarcomas

• Are believed to derive from precursor cells associated with the arrector muscles of the hair, the smooth muscle surrounding sweat glands or the genital dartos muscle

• The majority arise between 40 and 60 years of age, with a male predilection 

• Clinical findings
• Usually on the extremities, particularly on the hairbearing extensor surfaces and on the lower extremities
• Ill-defined, solitary swellings / nodules, smaller than 2 cm
• The overlying epidermis may exhibit a pink, purple, brown, or red discoloration; crusting; or ulceration
• As many as 95% of patients report pain in association with the lesion, although some report itching, burning or bleeding

• Management is surgical, a wide local excision is required as recurrence rates of 40% have been reported. Dermal lesions almost never metastasize

Subcutaneous leiomyosarcomas

• Are presumably derived from precursors in the muscular walls of veins and arteries

• The inferior vena cava and veins of the lower extremities are the most common sites

• There is a predilection for males

• Lesions are deep-seated, well-defined, nodular tumours or swellings, which expand rapidly and can ulcerate. The leg is the most common site

• Management is surgical. Subcutaneous lesions can metastasize quickly and have a mortality rate of about 30%

• Management is in Secondary / Tertiary care - any enlarging nodule of unknown diagnosis should be referred urgently (two-week wait)

• Treatment is with wide local excision