Abstract
Introduction: Myopericytoma is a rare perivascular neoplasm of soft tissue that arises from pericytes and exhibits a myoid differentiation. The etiology is non-specific but a prior history of trauma to the affected area is strongly associated with its formation. Additionally, immunosuppressed patients, such as those with an acquired immunodeficiency syndrome are at a higher risk. Myopericytoma presents as an unencapsulated, circumscribed, nodular mass composed of perivascular spindle-shaped myopericytes with an abundant network of blood vessels. Upon immunohistochemical staining, a tumor exhibits a strong affinity towards smooth muscle actin (SMA) and caldesmon. Cutaneous myopericytoma is an infrequent tumor that appears as a non-tender nodule on the lower distal extremities. Herein, we present a case of cutaneous myopericytoma arising on the distal left hallux of a middle-aged female.
Case Description: A 56-year-old white female with no significant past medical history presents to the office with a slowly enlarging mass on her distal left hallux for six months. On a physical examination, non-motile firm mass is present on the lateral aspect of the left distal digit. Mild drainage, erythema and tenderness are noted with a noticeable incurvation of the lateral border of the left hallux. Due to abnormal soft tissue findings on X-Rays and a high clinical suspicion of a bone or cartilaginous tumor, the patient is referred for a surgical excision along with the histopathological analysis. During the removal procedure by the podiatrist, the mass appears to be arising closely to the epidermis. Gross examination of the mass reveals a well-circumscribed, 1.0 x 0.5-cm, hypopigmented, white, firm mass. The neoplasm is avascular in nature and seems to be originating from the bone. Microscopic evaluation demonstrates a poorly circumscribed spindle cell neoplasm arranged in sweeping fascicles with a characteristic concentric pattern seen around blood vessels. The cells are fusiform, slightly eosinophilic and contain spindled nuclei with prominent nucleoli. Scattered typical mitosis figures are identified. The tumor cells are positive for smooth muscle actin (SMA) and negative for desmin, pankeratin, S-100, Factor 13a and CD-34. Thus, a diagnosis of cutaneous myopericytoma is established.
Discussion: Cutaneous myopericytoma is a rarely reported deep soft tissue tumor in the dermatologic literature. The majority of cases are benign, carry a low health risk, and rarely recur after a complete surgical excision. Most cases of the reported cutaneous myopericytomas present as solitary, non-painful, firm, gray to white in color lesions. In summary, we have described a novel case of cutaneous myopericytoma, which should be on a differential diagnosis list of neoplasms of lower extremities due to being a masquerader of common bone and cartilaginous tumors.
