OSSIFYING FIBROMYXOID TUMOR
This is a very uncommon tumorref 1 that occurs most frequently in the subcutis of an upper or lower extremity of  an adult. Exceptional examples have been reported from children and in other sites. These are thought to be of neural origin, but this interpretation is not conclusive. Few cases have been reported in the dermatologic literature. Local recurrence is common. Atypical as well as malignant variants have been describedref2 .

An incompletely ossified fibrous rim that may or may not be continuous surrounds a central cellular area in most cases. The  round tumor cells of medium size are relatively uniform in most areas, but spindle cell differentiation can  be present. The tumor cells  are often found in nests or clusters that are incompletely separated by delicate connective tissue. The clusters of cells can also be separated by a hyalinized fibrous matrix. Myxoid foci can occasionally be found within spindle or round cell areas, particularly in areas wherein a fibrous matrix is not prominent. Tumor cells are described as being S100 positive though the reaction may not be very strong.

The differential diagnosis includes a variety of neural, neural crest, and chondroid tumors, but the combination of features illustrated in this case is unique.


From an extremity of a 66 year old female:
 
Direct scan of the slide. The mass is subcutaneous and not connected to an underlying structure.
Medium power view that shows the predominant pattern of the tumor. Note the monotony of the cells and the tendency of the cells to form nests or clusters.
High power view of above. The cells are of medium size and are relatively uniform. Nuclei are centrally or eccentrically located. The cytoplasm is eosinophilic, amphophilic, or pale.
Medium power view showing a more collagenized area. The tendency to form clusters is more apparent in collagenized areas.
High power view showing myxoid stroma and less collagen.
High power view of an area composed of spindle and elliptical cells associated with myxoid stroma.
Medium power view showing bone and tumor.
Note: This case was sent to me about eight years ago by Dr. Frank Hatch. I was not sure what it was and suggested that he seek further consultation. He sent sections to Dr. Sharon W. Weiss (one of the authors of the original article describing this) who identified it.

References:
1. Enzinger FM, Weiss SW, Liang CY.
    Ossifying fibromyxoid tumor of soft parts. A clinicopathological analysis of 59 cases.
    Am J Surg Pathol. 1989 Oct;13(10):817-27.

2. Kilpatrick SE, Ward WG, Mozes M, Miettinen M, Fukunaga M, Fletcher CD.
    Atypical and malignant variants of ossifying fibromyxoid tumor. Clinicopathologic  analysis of six cases.
    Am J Surg Pathol. 1995 Sep;19(9):1039-46

Click on your browser's 'Back' button to return to the previous page.