Leiomyosarcoma

Summary: Introduction

•Leiomyosarcoma (LMS) is a malignant spindle cell neoplasm. Cutaneous LMS is a superficial variant of this uncommon soft tissue sarcoma.

M. Rubenzik • B. Limthongkul • T.R. Humphreys (*) Department of Dermatology, Thomas Jefferson University, Philadelphia, PA, USA

e-mail: tatyana.humphreys@jefferson.edu

23.1 Introduction

Leiomyosarcoma (LMS) is a rare malignant spindle cell neoplasm. Whereas the most common locations are uterine and retroperitoneal, LMS of the skin accounts for only about 2% of all soft tissue sarcomas [1]. LMS of the skin and subcutaneous tissue is usually designated as “superficial” in contrast to deep soft tissue sarcomas [2]. While cutaneous LMS can be a either primary or metastatic, the scope of this chapter is limited to treatment of primary cutaneous tumors. Primary skin LMS have been further divided histologically into cutaneous and subcutaneous based on the observed biological potential and prognostic values of each designation.

Summary: Clinical Features

•Cutaneous LMS typically presents as a firm subcutaneous nodule on the head, neck, extremities, or trunk that is relatively nonspecific in appearance. Erythema and ulceration may be present.

23.2 Clinical Features

In a recent large review of cutaneous soft tissue sarcomas, LMS was reported to occur most frequently on the head and neck (32%), followed by the trunk, arms, and legs (20%) [1]. Because they are derived from arrector pili, cutaneous leiomyosarcoma can theoretically occur on any hair-bearing skin surface, whereas the vascularderived subcutaneous LMS can occur on any body site. Recent studies suggest that subcutaneous LMS predominantly occurs on the lower extremities, whereas the cutaneous variant presents more frequently on the head and neck (48%), followed by the extremities (31%), then the trunk (21%) [2]. Men are more commonly affected (74%) as are Caucasians (91%) [1]. The incidence of LMS increases linearly with patient age [1].

Primary LMS is typically a solitary indolent neoplasm that presents as a cutaneous nodule. Overlying

erythema or discoloration occurs frequently [3, 4] while ulceration is uncommon. Like its benign leiomyoma counterpart, pain may be a presenting symptom [5]. In a recent study, the size at diagnosis ranged from 6 to 38 mm [6]. The clinical differential diagnosis includes any cutaneous or subcutaneous nodule such as a cyst, fibroma, lipoma, pseudolymphoma, lymphoma, neurofibroma, dermatofibroma, granuloma, and various subcutaneous malignancies [3].

While the etiology of LMS is unclear, it has been anecdotally associated with various types of trauma, including ionizing radiation, tick bite, inoculation site, venous stasis, and cutaneous tuberculosis [3]. Malignant transformation of benign leiomyomas has not been reported to date [3].

Summary: Histologic Features

•LMS is a spindle cell neoplasm with an infiltrative growth pattern. The tumor cells are blunt-ended with tapered nuclei, characteristic of smooth muscle morphology. While cytologic atypia is variable, an infiltrating pattern with subcutaneous extension supports a diagnosis of LMS rather than leiomyoma. LMS typically stains positively for vimentin, desmin, smooth muscle actin, and H-caldesmon.