Acral myxoinflammatory fibroblastic
sarcoma is a unique low-grade
tumor of modified fibroblasts. It characteristically occurs in the distal extremities and has a propensity to recur locally. Forty-four cases that occurred in 22 males and 22 females from 20 to 91 years of age (median, 53 years) were studied. The lesions, which were 1-6 cm (median, 3 cm), occurred in the hands (64%), the feet (20%), the ankles (11%), and the wrists (5%). The patients usually had a long history of a painless mass (median duration, 1 year). Clinically they were suspected to be
ganglion cysts, tenosyonovitis, or
giant cell tumors of tendon sheath. Initial histologic diagnoses, in most cases, included pigmented villonodular
tenosynovitis or various reactive fibroinflammatory processes. Histologically, the lesions were multinodular, poorly delineated, and characterized by a prominent myxoid matrix containing numerous inflammatory cells, including polymorphonuclear leukocytes, eosinophils, lymphocytes, and plasma cells, as well as
fibrosis. Amidst the prominent
inflammation, and sometimes obscured by it, were scattered, large, bizarre
tumor cells with vesicular nuclei, prominent inclusion-like nucleoli, and abundant eosinophilic cytoplasm, which was homogeneous to vacuolated and often contained intracytoplasmic inflammatory cells. Ultrastructurally, the bizarre
tumor cells had features of modified fibroblasts, including an abundance of intermediate filaments and dilated rough endoplasmic reticulum. Immunohistochemically, the neoplastic cells revealed strong positivity for
vimentin (25 of 25), focal positivity for
CD68 antigen (17 of 25) and CD34 (7 of 25); the
tumor cells did not express neuroectodermal, epithelial, or lymphoid markers. The Ki67 labeling index with MIB1 was less than 1% in 20 of 25 cases; p53 immunoreactivity (20-90%) was observed in 7 of 25 primary
tumors and in 2 of 3 local recurrences. Follow-up information was available in 36 of 44 cases (median, 5 years). Most excisions were either intralesional or marginal. Ten patients underwent
amputation, usually after repeated local recurrences.
Radiation therapy and
chemotherapy were administered in five and two cases, respectively. Twenty-four cases (67%) had at least one local recurrence. A histologically proven
lymph node metastasis developed in one patient, whereas another was stated to have lung
metastases, although these were not documented histologically. At last follow-up, 23 patients were alive and well, 11 were alive with disease, and 2 were dead of other causes without evidence of
tumor. The prominent
inflammation and
fibrosis seen histologically in acral myxoinflammatory fibroblastic
sarcoma simulate a reactive process. The presence of myxoid foci and scattered bizarre cells, which are occasionally multivacuolated, may cause
confusion with
malignant fibrous histiocytoma and
liposarcoma. Based on the protracted
clinical course, a high rate of local recurrence (sometimes necessitating
amputation), and a low rate of
metastasis, we believe these
tumors are low-grade
sarcomas. The intimate relationship with the synovium, the frequent association with
tenosynovitis, and the prominent inflammatory infiltrate suggest that
inflammation may play a role in the pathogenesis of acral myxoinflammatory fibroblastic
sarcoma.