Superficial acral fibromyxoma: a clinicopathological study of new 41 cases from the U.K.: should myxoma (NOS) and fibroma (NOS) continue as part of 21st-century reporting?

BACKGROUND

Superficial acral fibromyxoma (SAF) remains poorly recognized by general pathologists and dermatopathologists, partly attributable to its relatively uncommon occurrence and recent documentation.

OBJECTIVES

To examine a series of SAF and document the U.K. experience with this new entity.

METHODS

We reviewed 771 tumours reported between 1970 and 2006 in seven different U.K. hospitals and coded as myxoma, not otherwise specified (NOS), fibroma (NOS) or dermatofibroma (NOS) presenting at acral sites. Forty-one cases of SAF were studied.

RESULTS

The patients comprised 27 men and 14 women, age range 19-91 years (mean 50, median 47), presenting with a solitary mass or nodule with a mean size of 1.92 cm. The common clinical sites were the toes (n=29) and fingers (n=11) as well as the palm (n=1), with more than 75% of cases close to or involving the nail bed. All cases presented with a painless mass except for four cases where pain was the presenting complaint. A history of trauma was reported in only two cases. Histologically, all cases presented as proliferation of spindle-shaped and/or stellate cells with a storiform and fascicular pattern embedded in a fibromyxoid/collagenous stroma with conspicuous mast cells. Multinucleated cells were observed (n=22), increased number of blood vessels in the stroma and extravasation of red blood cells (n=4). The characteristic immunophenotype was CD34+, CD99+/-, epithelial membrane antigen+ focally/-, S100-, desmin-, smooth muscle actin-, HMB45- and cytokeratin-.

CONCLUSIONS

We describe a large series of 41 cases of SAF showing that it is a distinct entity with typical clinical, histological and immunohistochemical features. Follow-up was available only in 12 patients, precluding a firm comment on recurrence. However, complete excision and follow-up review is recommended.