Ossifying fibromyxoid tumour of soft parts

Definition

A rare tumour of soft tissue of unknown histogenesis with a lobular architecture, predominantly of epithelioid cytology, with cells arranged in cords or trabeculae, a myxocollagenous stroma and often peripheral metaplastic bone formation. Childhood tumours, deep tumours and tumours with atypical features arguably have alternative diagnoses1.

Epidemiology

This is a rare tumour, with approximately 320 cases reported in the published literature. There is a mid male predominance. Patients have a mean age of 50 years and a range of 20 to 80 years.

Clinical features

The tumour is most commonly located on the lower extremity. It presents as a slow growing painless mass, often present for years prior to surgery.

Radiology

Radiology will commonly show the peripheral ossification.

Macroscopic appearances

The tumour is subcutaneous. It does not involve muscle except for superficial musculature if on the face. Rarely, there is extension into the dermis. It is circumscribed with a dense fibrous pseudocapsule, sometimes lobulated. It is firm, usually with a glistening cut surface.

Histopathology

It is composed of lobulated nests of small bland round cells within a stroma which varies from myxoid to hyaline. The lobules are separated by fibrous septa. Most, but not all, cases have a layer of bone spicules peripherally, which may be of variable extent. (In one case, the bone was located centrally4.) The bone may incorporate fat but not haemopoietic tissue. The bone may be associated with a multinucleate giant cell component. There are often zones of hyalinisation. Some cases who necrosis.

The tumour cells form cords / trabeculae but not glands. The cells are predominantly epithelioid but may be focally spindled. Cytoplasm is pale to eosinophilic. Nuclei are fairly uniform with small central nucleoli. There may be occasional nuclear grooves or pseudoinclusions. The mitotic count is variable, up to 40 / 50 HPF, without atypical mitoses.

Immunohistochemistry

Ultrastructure

Cells show external lamella2. There are primitive intercellular junctions2.

Differential diagnosis

• Cutaneous mixed tumours

• Low-grade fibromyxoid sarcoma: the cells are predominantly spindled, forming whorled or storiform patterns; there ay be hyaline rosettes: S-100 is negative: there is a t(7;16) translocation3.

• Extra-skeletal osteosarcoma

• Epithelioid smooth muscle tumour

• Epithelioid Schwannoma

• Glomus tumour

• Chondroid syringoma

• Soft tissue aneurysmal bone cyst

• Sclerosing epithelioid fibrosarcoma

• Chondromyxoid tumours arising from nasal cartilage

• Myxoid chondrosarcoma

• Reticular perineuroma

• Primary bone tumours

Management

Complete local excision with a margin.

Prognosis

About 20% of cases recur, often after an interval of years. A mitotic rate of greater than 2 / 50 HPF predicts local recurrence. If strict diagnostic criteria are applied, the tumour does not metastasis1: other authors have reported atypical cases to as developing distant metastases.

References

0 Diagnostic Immunohistochemistry edited by Professor D. J. Dabbs, pages 77

1 Miettinen M, Finnell V,Fetsch JF. Ossifying fibromyxoid tumor of soft parts--a clinicopathologic and immunohistochemical study of 104 cases with long-term follow-up and a critical review of the literature. Am J Surg Pathol 2008; 32:996-1005

2 Min KW, Seo IS,Pitha J. Ossifying fibromyxoid tumor: modified myoepithelial cell tumor? Report of three cases with immunohistochemical and electron microscopic studies. Ultrastruct Pathol 2005; 29:535-48

3 Reid R, de Silva MV, Paterson L, et al. Low-grade fibromyxoid sarcoma and hyalinizing spindle cell tumor with giant rosettes share a common t(7;16)(q34;p11) translocation. Am J Surg Pathol 2003; 27:1229-36

4 Holck S, Pedersen JG, Ackermann T, et al. Ossifying fibromyxoid tumour of soft parts, with focus on unusual clinicopathological features. Histopathology 2003; 42:599-604

This page last revised 14.7.2008.

©SMUHT/PW Bishop