WHAT IS THIS FIRM NODULE ON A HEALTHY YOUNG WOMAN?
A 37-year-old woman presented with a firm nodule on her left shoulder that had been present for several months and was currently increasing in size. She denied any pain or tenderness at the site. The patient also denied any recent trauma or bite to the area. She was otherwise healthy and denied any other medical problems. On physical examination, the patient had a 1.7 cm x 1.8 cm erythematous nodule with scattered telangiectasias on the left superior shoulder. Aside from diffuse chronic solar damage, no other suspicious areas were noted. The patient had no palpable anterior cervical, supraclavicular or axillary lymphadenopathy. The nodule was biopsied and the histological findings were evaluated. ___________________________
DIAGNOSIS: CUTANEOUS LEIOMYOSARCOMA
Cutaneous leiomyosarcoma is a rare spindle-cell neoplasm characterized by an infiltrative growth pattern.1 Superficial leiomyosarcomas are categorized as cutaneous and subcutaneous; both are rare, comprising approximately 3% to 4% of soft tissue sarcomas, with perhaps as few as 125 cases reported in the English literature.2,3,4 Metastasis of cutaneous leiomyosarcoma is uncommon but has been reported.5 In addition, the cutaneous variant is often smaller than the subcutaneous counterpart. The subcutaneous counterpart carries a higher risk of metastases, with the lungs being the most commonly affected site. Treatment for leiomyosarcoma thus largely depends on the classification of the tumor in addition to its location. Leiomyosarcomas may present at any age, but they most commonly affect people in their 4th to 6th decades. While these tumors may arise anywhere on the body, there is a predilection for the involvement of the extremities. Clinicopathology Cutaneous leiomyosarcomas are thought to arise from the arrector muscles of pilosebaceous units.1 Leiomyosarcomas may also arise from smooth muscle of the subcutaneous vasculature, gastrointestinal tract, or retroperitoneum.6 It is worth noting that the term cutaneous implies dermal, which is a common source of confusion in its classification. The diagnosis of leiomyosarcoma may be made with histolopathological and imunohistochemical examination. These tumors appear as dense collections of spindle-shaped cells with eosinophilic cytoplasm.2 Leiomyosarcoma tumors can be difficult to distinguish histologically from other dermal spindle cell neoplasms (spindle cell squamous cell carcinoma, spindle cell melanoma, desmoplastic melanoma, atypical fibroxanthoma, malignant fibrous histiocytoma, etc.). Immunostains such as actin, desmin, cyotkeratin, S-100 protein and CD68 may be useful in this distinction. Differential Diagnosis The clinical differential diagnoses include dermatofibroma, dermatofibromasarcoma protuberans, malignant fibrous histiocytoma, and infiltrating basal cell or squamous cell carcinoma.1 Multiple lesions may be a sign of distant metastasis from a deep-seated leiomyosarcoma. However, metastasis to the skin is an uncommon and ominous manifestation.5 Imaging of soft tissue sarcomas is typically performed with MRI due to its superior tissue discrimination and multiplanar imaging capability.8 The borders of superficial leiomyosarcomas are better defined than their subcutaneous counterparts.8 Treatment Treatment for cutaneous leiomyosarcoma consists of wide local excision with wide margins. Surgical margins with traditional wide local excisions range from 1 cm to 3 cm; however, this has largely been replaced with Mohs micrographic surgery. The reported recurrence rate following wide local excision is approximately 30% to 45%.1 The use of Mohs micrographic surgery represents the optimal treatment modality, demonstrating a recurrence rate of 13%.1 In such cases, modified Mohs techniques are commonly used, which include the use of rush paraffin sections either with each stage or after surgical clearance with frozen sections. Summary Rouhani et al reported an exponential increase of leiomyosarcoma from 1980 to 2004.9 Leiomyosarcoma should remain in the differential diagnosis of cutaneous neoplasms. Histologic identification, imaging and surgical treatment should follow clinical suspicion of these lesions. Robert Lott, BS, is a medical student at Mercer University School of Medicine, Macon, GA. Dr. Lane is with the Division of Dermatology, at Mercer University School of Medicine, Macon, GA, as well as The Medical College of Georgia, Augusta, GA. He is also with the Department of Dermatology at Emory University School of Medicine, Atlanta, GA. Dr. Khachemoune, the Section Editor of Derm Dx, is with the Department of Dermatology, State University of New York, Brooklyn, NY. Disclosure: The authors have no conflicts of interest to disclose.