Myopericytoma

Definition

The term myopericytoma was first proposed in 1996 by Requena as an alternative designation for solitary myofibroma. It was adopted in 1998 by McMenamin and Fletcher to describe a spectrum of tumours with striking concentric perivascular proliferation of spindle cells (perivascular myoid cells, pericytes).

This spectrum includes:

• infantile-type myofibromatosis: there is a biphasic appearance of primitive spindle cells around blood vessels and myoid/myofibroblastic areas. Mitoses and apoptotic figures are frequent and there may be necrosis. However, pleomorphism is absent. The concentric perivascular growth pattern is not prominent.

• solitary myofibroma

• benign myopericytoma: occur over a wide age range, typically in subcutaneous tissues of the extremities. Lesions may be multiple within an anatomical region. These tumours are well-circumscribed. There is a perivascular growth pattern. Necrosis and cytological atypia are lacking and mitoses are infrequent.

• malignant myopericytoma

• infantile haemangiopericytoma

• glomangiopericytoma.

Excluded are:

• pure glomus cells tumours, and glomangiosarcomas, which do not show the concentric growth pattern and usually lack spindle cells.

• sinonasal-type haemangiopericytoma

Clinical features

Myopericytoma occurs across a wide age range from the second decade onwards, with a male predominance. It is occurs in the dermis and superficial soft tissues and is most common in the lower extremity, followed by the upper extremity, head and neck and trunk. Some patients have multiple tumours.

Histopathology

Myopericytoma is usually well circumscribed. There are numerous thin-walled blood vessels with walls of ovoid plump spindle cells. The cells have eosinophilic cytoplasm and grow in a conspicuously concentric pattern around the vessels. Some cases are haemangiopericytoma-like, numerous dilated branching vessels, which are similarly surrounded by spindle cells. Some cases resemble angioleiomyoma. Less cellular cases with a prominent collagenous stroma are fibroma-like. There may be areas indistinguishable from glomangioma. Yet other cases appear to be intravascular.

Malignancy is associated with an infiltrating growth pattern, cytological atypia and mitotic activity.

Immunohistochemistry

Differential diagnosis

• Glomus tumour: lacks spindle cells

Prognosis

Even with marginal excision, local recurrences are uncommon.

References

1 McMenamin, M. E. and C. D. Fletcher (2002). "Malignant myopericytoma: expanding the spectrum of tumours with myopericytic differentiation." Histopathology 41(5): 450-60.

2 Mentzel T, Tos AP, Sapi Z, et al. Myopericytoma of Skin and Soft Tissues: Clinicopathologic and Immunohistochemical Study of 54 Cases. Am J Surg Pathol 2006; 30:104-113

This page last revised 28.1.2006.

©SMUHT/PW Bishop