Introduction

Cutaneous Leiomyosarcomas (CL) are a rare subset, constituting a mere 3% of malignant soft tissue sarcomas(1). Within superficial leiomyosarcomas, two distinctive forms exist—cutaneous and subcutaneous(2). Typically presenting as skin nodules, precise diagnosis requires histopathological examination complemented by immunohistochemistry. This case report outlines an instance of cutaneous leiomyosarcoma in the forearm of a 40-year-old male.

Case Presentation

A 40-year-old male presented with a forearm nodule persisting for a year, with a history of a similar swelling three years prior, excised without available reports. On examination, the 3 x 3 cm swelling displayed firm consistency with unremarkable overlying skin. A 0.5 x 0.4 x 0.3 cm skin biopsy revealed a dermal neoplasm, comprising atypical spindle cells exhibiting palisading in fascicles and bundles (Figure.1). Individual cells featured eosinophilic cytoplasm, pleomorphic, and hyperchromatic nuclei (Figure.2). Focal areas of necrosis and a mitotic count of approximately 28 mitoses/10 high power fields were noted. Immunohistochemical analysis confirmed positivity for smooth muscle actin (Figure.3) and negativity for S100 (Figure.4), establishing a diagnosis of cutaneous leiomyosarcoma. Subsequent wide resection confirmed tumor-free margins.

Figure 1: Dermal neoplasm showed composed of atypical spindle cells arranged in fascicles and bundles with palisading.(100x)	Figure 2: Atypical spindle cells with eosinophilic cytoplasm, pleomorphic and hyperchromatic nuclei.(400 x)
Figure 3: Immunohistochemistry - The tumor cells showing strong positivity for Smooth Muscle Actin (100 x)	Figure 4: Immunohistochemistry - The tumor cells negative for S100 (100 x)

Discussion

Comprising a mere 3% of malignant soft tissue sarcomas(1), Cutaneous Leiomyosarcomas predominantly affects the elderly(3), with a male predilection and extremities being the most common location(4). Clinically, nodular growth is characteristic(5). Histologically, Cutaneous Leiomyosarcomas is defined by palisading spindle-shaped tumor cells with cigar-shaped nuclei and atypia, frequent mitotic figures, and areas of necrosis. Differential diagnoses encompass spindle cell lesions such as peripheral nerve sheath tumors, fibrosarcoma, synovial sarcoma, and dermatofibrosarcoma protuberans. Immunohistochemistry plays a pivotal role in precise diagnosis, demonstrating positivity for vimentin, desmin, and smooth muscle actin in Cutaneous Leiomyosarcomas, while neural origin lesions exhibit S100 positivity.

Recommended treatment involves wide excision(6,7), but recurrences are common(8). Distant metastasis, primarily to the lungs(1,5), and poor prognostic factors such as lesion size, fascial involvement, inadequate margin clearance, extremity location, and high histological grade are significant considerations. Subcutaneous Cutaneous Leiomyosarcomas poses higher risks of local recurrence and metastasis. The role of radiotherapy is emphasized to reduce relapse, while chemotherapy administration remains contentious. Pazopanib, a tyrosine kinase inhibitor targeting VEGF and PDGF, is FDA-approved for advanced cases.

Conclusion

In the domain of malignant spindle cell neoplasms of the skin, cutaneous leiomyosarcoma, though rare, demands consideration and confirmation through a comprehensive IHC panel. Awareness of prognostic factors guides tailored management, advocating for a multidisciplinary approach to ensure optimal patient outcomes.

References

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