MYOFIBROMATOSIS IN ADULTS, GLOMANGIOPERICYTOMA, AND MYOPERICYTOMA - ASPECTRUM OF TUMORS SHOWING PERIVASCULAR MYOID DIFFERENTIATION

The clinicopathologic features of 24 tumors showing perivascular myoid differentiation are described. These included tumors with histologic features of ''infantile-type'' myofibromatosis occurring in adult pati ents (8 cases), tumors with composite features of ''hemangiopericytoma '' and glomus tumor (9 cases), and tumors with a distinctive concentri c perivascular proliferation of spindle cells. (7 cases). Evidence of morphologic overlap among these groups suggests they are closely relat ed neoplasms that form a single spectrum. Age of patients with lesions resembling infantile-type myofibromatosis ranged from 23 to 67 years (median, 37 years). Clinicopathologic manifestations of this disease i ncluded multicentricity (4 cases), local recurrence (3 cases), persist ance of congenital lesions into adulthood (4 cases), and tumors that w ere multifocal within the confines of one anatomic region. Histologica lly, all cases showed a biphasic pattern that consisted of fascicles o f spindle cells with abundant eosinophilic cytoplasm that resemble smo oth muscle, in addition to a population of more primitive spindled cel ls associated with hemangiopericytoma-like vascular pattern. Six cases showed reversal of the typical zonation seen in pediatric cases in th at the primitive component surrounded the more mature fascicular areas . Also described are nine tumors with features that are intermediate b etween glomus tumor and hemangiopericytoma, which we have designated g lomangiopericytoma. These tumors are characterized by prominent branch ing vessels lined by a single row of endothelial cells surrounded by e pithelioid cells with a glomoid appearance. In other areas, the tumors showed typical hemangiopericytomatous foci similar to those in the my ofibromatosis cases. The principal points of distinction were a lack o f myoid nodules and an absence of small primitive cells with basophili c cytoplasm. Ages of these patients ranged from 17 to 78 years (median , 35 years). All tumors were located in the subcutaneous tissue and th e superficial soft tissue of the extremities. Recurrence developed in one of six patients with follow-up information. The recurrent tumor ha d features of angiomatoid malignant fibrous histiocytoma. Finally, we describe a subset of tumors characterized by concentric periluminal pr oliferation of bland, round to ovoid cells, which we have designated a s myopericytoma. Patients ages ranged from 10 to 66 years (median, 40 years). All were located in subcutaneous and superficial soft tissue o f distal extremities. One patient had two recurrences in 3 years after initial excision. Our study suggests that these three lesional groups comprise a histologic continuum of tumors that share clinical similar ities and that, perhaps, are designated more appropriately as perivasc ular myomas. The relationship of this family of tumors to so-called he mangiopericytomas is discussed.