Leiomyosarcoma C49.-

Malignant tumour of the smooth musculature, mostly originating from hair follicle muscles but also from the vascular musculature.

There are 6 types of leiomyosarcoma, which differ significantly in dignity and clinical presentation (also localization).

In dermatology only types 1-4 are of interest for differential diagnostic reasons; in addition, some variants are separated which are mainly characterized by histological features:

1. Cutaneous (pilary) leiomyosarcoma: Favourable prognosis, tendency to local recurrence (15%)
2. Subcutaneous leiomyosarcoma: Poor prognosis and tendency to early (15%) metastasis (regional lymph nodes, lung)
3. Vascular Leiomyosarcoma (5%)
4. Genital Leiomyosarcoma (5%)
5. Intraabdominal leiomyosarcoma (40%)
6. Deep leiomyosarcoma of the extremities (20%).

Histological variants:

• Myxoid leiomyosarcoma (often in the genital area)
• Granular cell leiomyosarcoma (histological diagnosis)
• Leiomyosarcoma with prominent osteoclast-like giant cells (giant cell variant of the leiomyosarcoma with an extremely poor prognosis)
• Sclerotic leiomyosarcoma (clinically keloid-like)
• Epithelioid leiomyosarcoma (no clinical feature).

Leiomyosarcomas account for about 10% of the total number of soft tissue sarcomas. After dermatofibrosarcoma protuberans, leiomyosarcoma is the second most common sarcoma. Incidence rates are given as 0.2/100,000 persons/year.

Occurrence is possible at any age. After the age of 60 the occurrence is slightly more frequent than in younger patients. A few cases of leiomyosarcoma have been observed in connection with post-transplant lymphoproliferative disease and EBV infection(Aida N et al. 2019)

Clinic of dermal and subcutaneous leiomyosarcoma:

• Cutaneous leiomyosarcomas present as 2.0-5.0 cm plaques or nodules, which can be painful (like leiomyosarcomas). They can be displaced against the underlying tissue and fused with the covering dermis.
• Note: It has been shown that the prognosis of these smooth muscular tumours depends on their depth of penetration. Dermal tumours rarely recur and never metastasise. Therefore the name:"atypical smooth muscle tumour of the skin" has been suggested. Once subcutaneous infiltration is present, they have metastatic potential.
• The pilary leiomyosarcomas (mainly on the lower extremity) are impressive as rough, sharply defined tumor masses; they tend to superficial ulceration.

Mostly blurred nodules (dermal or subcutaneous) with infiltrating, destructive growth and with the histological and immunohistological characteristics of smooth muscles. Typical is a fascicular structure with high cellularity. A spindle-shaped cell type, usually with strong eosinophilic cytoplasm, which is organized in nests and bundles, is impressive. Storiform or palisade-like structures may occur. A distinct nuclear polymorphism is usually prominent, as well as multinucleated giant cells and numerous pathological mitosis figures. Monstrous giant cells may dominate the histological picture in some variants (leiomyosarcoma with prominent osteoclast-like giant cells).

Immunohistology: reactivity for smooth muscle actin and (inconstant) desmin. h- caldesmon +; cytokeratin +/-.

Superficial leiomyosarcomas metastasize very rarely. Local recurrences of 25-30% are reported with inadequate therapy. With a moderate follow-up period, the metastasis rate is 4.2% and the mortality rate 3.3% (Aneiros-Fernandez I et al. 2016).

With deeper infiltrating leiomyosarcoma the prognosis is significantly worse. In larger studies, metastasis rates (mainly metastases in the lung) of up to 43% are reported. The mortality rates are 37% with a mean follow-up period of 4.4 years (Aneiros-Fernandez I et al. 2016).

Metastasis is spread to the regional lymph nodes at an early stage. Hematogenic metastasis into the lungs is also possible, especially in the case of subcutaneous tumors. High local recurrence rate.

1. Aida N et al (2019) A Case of Epstein-Barr Virus-Associated Leiomyosarcoma Concurrently With Posttransplant Lymphoproliferative Disorders After Renal Transplantation. Clin Med Insights Case Rep 12:1179547619867330.
2. Aneiros-Fernandez J et al (2016) Primary cutaneous and subcutaneous leiomyosarcomas: evolution and prognostic
3. factors. Eur J Dermatol 26: 9-12.
4. Atinok G et al (2002) Primary leiomyosarcomas of the skin. Scand J Plast Reconstr Surg Hand Surg 36: 56-59
5. Humphreys TR et al (2004) Superficial leiomyosarcoma treated with Mohs micrographic surgery. Dermatol Surgery 30: 108-112
6. Kohlmeyer S et al (2017) Cutaneous sarcomas. J Dtsch Dermatol Ges 15: 630-647
7. Kuflik JH et al (2003) Dermal leiomyosarcoma. J Am Acad Dermatol 48(5 Suppl): S51-53
8. Schadendorf D et al (1993) Primary leiomyosarcoma of the skin. Acta Derm Venereol 73: 143-145
9. Stieler W et al (1991) Primary cutaneous leiomyosarcoma. dermatologist 42: 44-47