Fibromyxoid sarcoma of the leg.

A 48-year-old female with an atypical plaque-like lesion of the lower leg is presented in this article. Histologic investigation revealed a rare low-grade fibromyxoid sarcoma (pT1a cN0 cM0; stage Ia) of suprafascial localization. Staging of the patient did not reveal metastatic spread. The tumor was surgically removed with wide safety margins. The defect was closed using a mesh graft transplant and vacuum-assisted closure. Healing was complete. Regular follow-up for at least 5 years is recommended. Besides the rareness of this tumor, this case is also remarkable because of the localization on the lower leg and the suprafascial soft tissue.

INTRODUCTION

Sarcomas are mesenchymal neoplasms with various lines of differentiation, i.e., fibrocytic, myogenic, neurogenic, vascular, chondro-osseus, or undefined. The low-grade fibromyxoid sarcoma (LGFS) is a very rare entity. It is a spindle-cell tumor composed of collagen-rich and myxoid parts.[12] About 40% of these tumors also develop collagen rosettes.[3]

LGFS prefers subfascial soft tissue layers on the trunk and proximal extremities in younger adults but can also develop in internal organs. Pediatric cases have also been reported.[1-3]

Herein, we present a 48-year-old female patient who developed a LGFS on the lower leg. The clinical presentation, histopathology, surgical treatment, and follow-up are discussed.

CASE REPORT

A 48-year-old woman was referred to our department because she had developed a slow-growing plaque below the left knee for 2 years. A diagnostic biopsy had been taken by the referring dermatologist that suggested an LGFS.

On examination we found an otherwise healthy, slim, woman with a symptomless firm subcutaneous plaque of about 2 cm size on the anterior aspect of the left lower leg Figure 1.There was some bluish discoloration and circumscribed ulceration but no erythema or warmth.

Figure 1

Low-grade fibromyxoid sarcoma of the left lower leg. (a) Overview and (b) the ulcerated honeycomb-like plaque

Routine laboratory tests were unremarkable. Thoracic dual-energy x-ray and abdominal and lymph node ultrasound excluded a metastatic spread. Histology revealed a spindle-cell tumor, with mild atypia and fibroblast-like morphology [Figure 2]. The eosinophilic cells did not show increased mitotic activity. Cells were arranged in a whorled or plexifiorm pattern, with alternating collagenous stroma and myxoid zones. The cells stained positively for vimentin, but were negative for CD34 and S100. The covering epidermis was partially ulcerated. A final diagnosis of Low GradeF ibromyxoid Sarcoma was reached. Under general anesthesia, the tumor was surgically removed with a wide safety margin (>3 cm). The defect was covered by a mesh graft transplant covered by vacuum-assisted closure (VAC™; KCI International) [Figure 3]. Compression stockings were prescribed to protect the transplant and prevent leg edema. A regular follow-up for at least 5 years was recommended after consultation with the referring dermatologist.

Figure 2

Histopathology. (a) Overview (H&E, ×4) and (b) detail (H&E, ×40)

Figure 3

Surgical procedure. (a) Wide excision of suprafascial soft tissue; (b) mesh graft transplantation; and (c) placement of microporous white sponge for vacuum-assisted closure above the transplant

DISCUSSION

LGFS is a very rare and distinctive type of fibrosarcoma that was first described by Evans in 1987.[1] There is a discrepancy between the bland histologic features with sparse mitotic figures and absent or mild nuclear and cellular pleomorphism and the anaplasia. The hyalinizing spindle-cell tumor with giant rosettes is considered a subtype of LGFS.[1-3] The tumor is further characterized by t(7;16)(q34;p11) translocation and fusion of FUS and CREB3L1 genes.[45] Tumor cell phenotype is positive for vimentin, EMA, CD99, and bcl-2, but negative for CD34, SMA, S-100, desmin, keratins, neuron-specific enolase, and CD177.[5] The differential diagnosis includes other types of sarcomas, myxoma, neurofibroma, peripheral sheath tumor, histocytoma, desmoid tumor, and others.[235]

LGFS usually presents as a painless, slow-growing, soft tissue malignancy. The diagnosis often is delayed - mainly because the patients do not seek treatment early. Folpe et al. (2000) reported that in 15% of patients a histologic diagnosis was delayed by >5 years. In our case the delay was >2 years.[3]

Although the histopathologic features suggest a low-grade malignancy, local recurrence is seen in more than 50% of patients and metastasis occurs in 6% of patients.[3] Tumor cell dormancy is responsible for very late metastasis in some patients, with 45 years being the longest period observed between primary surgery and metastasis.[67] Therefore, patients should be encouraged to have regular follow-up.

The present case did not show any subfascial involvement. Complete surgery with wide margins (>3 cm) is the most important procedure. We used a combination of mesh graft transplantation and vacuum-assisted closure to cover the large defect. It has been demonstrated recently that such a combination, with microporous sponge for vacuum-assisted closure, results in a significantly improved take rate.[8] The prognosis for superficial LGFS seems to be better than that for deep LGFS.[9]