Myopericytoma of the Facial Cheek

Abstract

Dear Editor: A 44-year-old woman presented with a painful, solitary nodule on her right cheek. She noticed the flesh-colored nodule several years prior, and the nodule expanded slowly in size. There was no history of trauma. The patient's past medical history and family history were unremarkable. Upon physical examination, a 0.5×0.7 cm-sized, skin-colored, firm nodule on the right cheek was seen (Fig. 1). The biopsy specimen revealed a concentric perivascular proliferation of blank, spindle-shaped myoid-appearing cells (Fig. 2A, B). Immunohistochemical stain showed diffuse immunoreactivity on smooth muscle actin and was negative for desmin (Fig. 2C, D). The CD34 stain highlighted only the endothelium of the vessel, but the perivascular concentric myoid tumor cells were not immunoreactive (Fig. 2E). From the clinicopathological findings, the diagnosis of myopericytoma (MPC) was made. Fig. 1 A 0.5×0.7 cm sized, skin-colored, subcutaneous nodule of the right cheek. Fig. 2 (A) Uncapsulated neoplasm situated in the subcutis (H&E, scanning view). (B) Proliferation of bland round to ovoid cells arranged in a concentric perivascular pattern and many thin-walled branching staghorn vessels (H&E, ×200). ... MPC is a rare, recently delineated tumor that originates from the perivascular myoid cells1. It was described by Granter et al.2 in 1998 and newly entered into a subgroup of perivascular tumors in the World Health Organization classification of soft tissue tumors3. MPCs are well-circumscribed and composed of a mixture of solid cellular areas intermixed with variable numbers of vascular channels. The latter are often elongated and display prominent branching, resulting in a stag-horn appearance. The cells in the solid areas are round, or short and spindle shaped with eosinophilic cytoplasm and vesicular nuclei. The presence of concentric layers of tumor cells around vascular channels resulting in a typical onion ring appearance is a hall mark of this tumor2. However, MPC tumors exhibits a broad spectrum of growth patterns: solid classic, hemangiopericytoma-like, angioleiomyoma-like, hypocellular fibroma-like, solitary fibrous tumor-like, glomus tumor-like, cellular immature, intravascular and malignant subtypes. The present case was classified as angioleiomyoma-like pattern. By immunohistochemistry, the neoplastic cells characteristically express muscle-specific actin, smooth muscle actin and h-caldesmon, and are negative for CD34 and desmin4. The differential diagnosis includes myofibroma/myofibromatosis, angioleiomyoma, or glomus tumors. Myofibroma/myofibromatosis shows a distinct biphasic pattern consisting of fascicles of spindle cells and immature appearing zones2. Although perivascular concentric growth pattern has been observed in a subset of angioleiomyoma, this is not the predominant histopathologic feature, and angioleiomyomas show positive reaction for desmin in the smooth muscle bundles. In contrast, MPC is usually negative or only focally positive for desmin5. Glomus tumors can be distinguished by tumor cells showing more abundant eosinophilic cytoplasm and distinct cell borders. In addition, glomus tumors lack the concentric orientations of tumor cells around vessels characteristic of MPC4. MPCs typically arise in subcutaneous tissue as single or multiple nodules on the extremities of adults, with only rare cases of multicentricity. MPC presents as a benign, slow-growing nodule, and may occasionally be painful. Tumors rarely exceed 2 cm in size. A rare malignant transformation has been reported as well5. Most MPCs do not recur following excision4. Our patient decided to leave her lesion untreated. Involvement of the face in MPC cases is previously undescribed in the Korean dermatologic literature. Presentation of this case of MPC on the cheek will aid others in recognizing this very rare entity.