Leiomyosarcoma

Abstract

Supeificial leiomyosarcomas are rare in the head and neck region. Because of the infrequent nature of soft tissue sarcomas in general, superficial leiomyosarcomas are often misdiagnosed on clinical grounds. Immunohistochemistry is essential for an accurate histologic diagnosis, and it should include a broad panel of antibody studies. With respect to differences in clinical appearance and biologic behavior, superficial leiomyosarcomas can be broadly classified as either cutaneous or subcutaneous; local control and overall survival are significantly more favorable in patients with the former. The primary treatment of a leiomyosarcoma is a wide surgical excision with an emphasis on negative margins. Treatment failures are usually attributable to a local recurrence. Systemic metastasis occurs in about one-third of patients with subcutaneous involvement. Although cutaneous leiomyosarcoma is considered a relatively more benign process with minimal metastatic potential, systemic metastasis is still possible. This wa s demonstrated in our case, as a recurrent cutaneous leiomyosarcoma metastasized to the lung. Proper management requires inclusion of this entity in the differential diagnosis, as well as familiarity with its clinical behavior. In this article, we review the literature on superficial leiomyosarcoma and discuss its epidemiology, presentation, clinical behavior, evaluation, tissue diagnosis, staging, and treatment.

Introduction

Lelomyosarcoma is one of a diverse group of soft tissue sarcomas that occur throughout the body. [1] Although it is generally regarded as a deep soft tissue tumor, leiomyosarcoma also occurs in the skin and subcutaneous tissues. [2] The diagnosis of superficial leiomyosarcoma is often delayed or missed clinically because of its infrequency. [3] The head and neck surgeon should retain some familiarity with these tumors because their clinical course and treatment are distinctly different from those of more common skin malignancies, such as squamous cell carcinomas and melanomas. [4] In this article, we describe a case of cutaneous leiomyosarcoma of the face that metastasized to the lung. We also discuss the appropriate diagnostic workup and management of this malignancy.

Case report

A 64-year-old man came to a Veterans Administration hospital with a 3-week history of a rapidly growing mass on the left nasal dorsum. The patient had earlier undergone two local resections of tumor at this site within the previous 12 months. His medical history was remarkable for chronic immunosuppression following a heart transplantation 10 years earlier. He also had end-stage renal disease secondary to cyclosporine toxicity and required hemodialysis.

The head and neck examination was remarkable for the presence of a painless, raised, rubbery, 2-cm lesion on the left nasal dorsum. The lesion was skin-colored and slightly mobile, and it featured an area of central concavity. The nasal cavity was uninvolved, and no cervical adenopathy was palpable. The remainder of the examination was normal. Computed tomography (CT) revealed the presence of a soft tissue mass with no bone involvement (figure 1). An incisional biopsy was suspicious for a fibrohistiocytic neoplasm. An elective excision was planned.

The patient underwent a wide local excision of the tumor with local advancement flap closure. Histologic evaluation with hematoxylin and cosin staining revealed a spindle-cell-type malignancy that originated in the dermis and extended down into the subcutaneous fat and muscle (figure 2). All surgical margins were negative. Immunohistochemical staining was positive for both smooth muscle actin and muscle-specific actin (HHF-35), but negative for cytokeratin (figure 3). The final pathologic diagnosis was a cutaneous leiomyosarcoma of the nodular type and of an intermediate grade.

External-beam radiation therapy was delivered postoperatively to the surgical site in 20 fractions; the total dose was 50 Gy. Eight months later, however, the patient was found on routine chest x-ray to have a right pleural mass. CT-guided needle biopsy revealed a metastatic leiomyosarcoma. The patient died several months later of complications related to his underlying cardiac disease.

Discussion

Epidemiology. Leiomyosarcomas are one of a diverse group of soft tissue sarcomas found in the head and neck. They are not common in either adults or children; they appear to carry a similar prognosis in both groups. Compared with head and neck soft tissue sarcomas, leiomyosarcomas have a somewhat intermediate prognosis; 5-year survival rates have been reported to range between 61 and 100%. [1,5,6]

Leiomyosarcomas of the skin account for only a small percentage of leiomyosarcomas as a whole. Superficial leiomyosarcomas carry a better long-term prognosis than deep neck leiomyosarcomas, which tend to be more aggressive and have a higher potential for systemic metastasis. [1]

Unlike the case with squamous cell carcinomas and melanomas, no definite causative factor for leiomyosarcomas and other soft tissue sarcomas has yet been identified. Correlations have been established between soft tissue sarcomas in general and factors such as radiation exposure, chemical exposure, and possibly trauma and sun exposure. Chromosomal defects have also been implicated; leiomyosarcomas have been associated with hereditary (bilateral) retinoblastoma, which appears to result directly from mutations or deletions in the RB 1 gene. [1] Oncogenes such as the ras nuclear oncogene and the p53 tumor suppressor gene have also been studied in soft tissue sarcomas, although none has been approved for diagnostic use. [7]

Presentation. The typical clinical picture of a superficial head and neck leiomyosarcoma is one of a slowly enlarging, tender mass on the face or scalp. [8] Most superficial leiomyosarcomas occur as solitary nodules, and the presence of multiple leiomyosarcomas should raise suspicion of a systemic metastasis from another site, such as the retroperitoneum. [9] The median age of affected individuals is 60 years, and the disease occurs twice as often in men as in women. [5]

The clinical presentation of a superficial leiomyosarcoma can vary depending on whether the tumor originates in the cutaneous or subcutaneous tissue. Cutaneous leiomyosarcomas are typically small ([less than]2 cm) and feature discoloration, ulceration, or umbilication of the skin. Subcutaneous leiomyosarcomas are typically faster-growing and larger at the initial presentation. Overlying skin changes can be minimal. Unlike leiomyosarcomas of the deep neck tissues, leiomyosarcomas of the skin are usually painful or tender. [8]

Because of the rarity of this malignancy, preoperative misdiagnosis is common. A superficial leiomyosarcoma can be mistaken for other skin malignancies, such as basal cell and squamous cell carcinomas.[10,11] The physical appearance of these tumors can be deceptively benign, and they can also be mistaken for nonmalignant conditions, such as nevi, granulomas, and keloids. [12]

Clinical behavior. As a whole, superficial leiomyosarcomas carry a better long-term prognosis than deep neck leiomyosarcomas, which tend to be fairly aggressive and have a high potential for systemic metastasis. [5,6] Among superficial leiomyosarcomas, however, a distinct difference has been reported in the biologic behavior of the different forms of the disease. In the largest series of superficial leiomyosarcomas reported, Fields and Helwig distinguished two forms based on the apparent site of origin. [8] Most contemporary descriptions of the disease adhere to this distinction of cutaneous versus subcutaneous. [4,13,14] In cutaneous leiomyosarcoma, the local recurrence rate appears to be about 40%. Leiomyosarcomas that originate in the subcutis recur more often--in approximately 50% of patients. When cutaneous leiomyosarcomas are considered according to their depth of invasion, the local control rate is even better for those with disease localized to the dermis (32% recurrence). Those cutaneous tumors that extend microscopically into the subcutaneous tissue have a 47% recurrence rate, a figure more consistent with that of primary subcutaneous tumors. [8]

The metastatic potential of cutaneous and subcutaneous forms also differs. Only sporadic reports of regional metastasis exist in reference to cutaneous or subcutaneous disease. [15] No distant metastasis from cutaneous leiomyosarcoma was reported in Fields and Helwig's series [8] or elsewhere in the literature. The likelihood of systemic metastasis appears to correlate with the depth of skin invasion, as leiomyosarcomas that originate in subcutaneous tissues metastasize systemically in one-third of cases. Mortality from subcutaneous leiomyosarcomas has been reported to range from 30 to 40%. [8]

Evaluation. CT remains the workhorse for the radiographic evaluation of leiomyosarcomas and other soft tissue sarcomas. CT is useful in determining tumor extent, planning surgical or radiation therapy, and assessing the presence of metastatic disease, particularly to the lungs. Magnetic resonance imaging might provide additional valuable information regarding neurovascular detail in deeply invasive lesions. Positron-emission tomography has been significantly correlated with tumor grade, although this diagnostic modality is not widely available. Plain x-rays are of little use in evaluating soft tissue sarcomas. [16]

Tissue diagnosis. Incisional biopsy is classically the recommended method of preoperative tissue diagnosis. Excisional biopsy can result in a local failure rate of up to 90% because of the tumor's pseudocapsule of compressed tissue and viable malignant cells. Fine-needle aspiration biopsy can be equally useful in experienced hands, although a sufficient quantity of tissue must be obtained. If enough material is aspirated to create a paraffin-embedded cell block, cytochemical and immunohistochemical stains can be readily performed, greatly increasing the diagnostic accuracy of fine-needle aspiration. [17]

Histologically, leiomyosarcomas are distinguished by the fact that they mimic the appearance of smooth muscle. Grossly, cutaneous leiomyosarcomas have a grey-white, whorled appearance on cut section. On histopathologic section, leiomyosarcomas typically display a proliferation of elongated spindle-shaped cells, blunt-ended cigarshaped nuclei, and eosinophilic cytoplasm. Leiomyosarcomas can be confused histologically with other spindle cell sarcomas, especially fibrosarcomas, malignant schwannomas, and malignant fibrous histiocytomas. [1]

Kaddu et al described two distinct histopathologic growth patterns in cutaneous leiomyosarcoma: nodular and diffuse. [2] In their series of 19 patients, nodular leiomyosarcomas were the more common type, and they typically appeared as slowly enlarging, solitary, discrete, smooth, firm, nonulcerated, and painless masses. Histologically, Kaddu et al found that nodular leiomyosarcomas were characterized by high cellularity and prominent necrosis and atypia. Diffuse lejomyosarcomas, on the other hand, typically had a less-well-defined contour on physical examination. Histologic criteria for malignancy in the diffuse type were often subtle, with well-differentiated cells, few mitotic figures, and inconspicuous cellular necrosis. [2] Other histologic variants have also been reported in the literature, including epithelioid, desmoplastic, granular, and myxoid types. [1,11,17-19]

Immunohistochemistry is essential for an accurate histologic diagnosis of soft tissue sarcoma subtypes. Leiomyosarcoma cells are frequently positive for vimentin, smooth muscle actin, and muscle-specific or pan-muscle actin. Desmin is slightly more variable and occurs in as few as 50% of cases. Cytokeratins occasionally stain positive in epithelioid variants, known as leiomyoblastomas. To avoid misdiagnosis in immunohistochemical testing, it is advisable to use a broad panel of antibodies, including actins (SMA and HHF-35), desmin, vimentin, cytokeratins, and S-100 protein. [1,11,14,17]

Staging. Most soft tissue sarcomas are classified according to the GTNM staging system as described by the American Joint Committee on Cancer. Tumor grade is the most important factor for predicting metastasis and/or recurrence of soft tissue sarcomas in general. Besides staging status, other negative prognostic factors for soft tissue sarcomas include positive bone involvement or surgical margins, age greater than 50 years, deep location, local recurrence, DNA aneuploidy, and aggressive histologic type. [20,21]

Treatment. The recommended treatment of leiomyosarcoma is primarily surgical and consists of a wide local excision with an emphasis on negative margins. [13] Treatment failures in the head and neck are usually attributable to local recurrence because of the relative difficulty of resection in this region. [21] Although elective neck dissection might be indicated for clinically positive lymph nodes, it is not typically recommended for the clinically NO neck because of the low overall incidence of regional metastasis. [5,6]

Adjuvant external-beam radiotherapy is indicated for all high-grade tumors, those with questionable or positive margins, and those larger than 5 cm. However, whether radiotherapy actually improves local control is still controversial.

No clear survival benefit has been shown with the use of chemotherapy in adult soft tissue sarcomas. [22.23] However, anecdotal success has been reported; Haffner et al described the successful treatment of one case of subcutaneous leiomyosarcoma with regional chemotherapy following an incomplete surgical excision. [24] They treated an elderly woman with disease of the lower extremity with tumor necrosis factor and melphalan and reported no evidence of recurrent disease at 2 years of followup.

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