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CD99 immuno-reactivity
in atypical fibroxanthoma and pleomorphic malignant fibrous
histiocytoma: a useful diagnostic marker.J
Cutan Pathol. 2006 Sep;33 Suppl 2:24-8.
Atypical
fibroxanthoma (AFX), a benign lesion, and pleomorphic malignant
fibrous histiocytoma (MFH) are thought to represent points along the
same neoplastic spectrum but with different prognoses and treatments.
Diagnosis based on histology and clinical parameters alone is
sometimes difficult, and a reliable cost-effective immunohistochemical
marker to help distinguish these lesions would be beneficial. The
diagnosis of AFX or MFH was based upon published clinical and
microscopic criteria. Formalin-fixed, paraffin-embedded tissues of 17
cases of AFX and 26 cases of MFH were immunostained with monoclonal
antibody to CD99. For all cases, CD99 expression was scored on a
four-tiered scale: negative, weak (1+), moderate (2+), or strong (3+).
Two pathologists blinded to tumor diagnoses and type of immunostain
evaluated each case independently. The interobserver correlation
coefficient was calculated. Seventeen patients with AFX (16 males and
one female; mean age = 79) and 26 patients with MFH (16 males and 10
females; mean age = 60) were included. AFX lesions were from the head
and the face, mean size = 1.5 cm, and MFH lesions were from the head,
the neck, the trunk, and the upper/lower extremities, mean size = 5.2
cm. The 17 cases of AFX demonstrated moderate or strong (2 to 3+)
immunoreactivity with CD99, compared to nine of 26 (35%) MFH cases
(chi-square = 18.38; p < 0.001; interobserver correlation coefficient
= 0.83). Of these, 16 of 17 (94%) AFX cases stained diffusely with
CD99, while only four of 26 (15%) MFH cases stained diffusely. Control
slides were adequate. Our study demonstrated that CD99 can help
distinguish AFX from MFH, in addition to other immuno- histochemistry
as well as clinical and histologic criteria. |
