Letter to the Editor
To the Editor:
We read with great interest the article entitled “CD117 is Not a Useful Marker for Diagnosing Atypical Fibroxanthoma” by Beer and Haig in the October 2009 issue. The authors reviewed 50 cases of atypical fibroxanthoma (AFX) and evaluated them with immunostains for CD117, S100, CD1a, and tryptase. Only 1 of the 50 AFXs in their series showed positive staining of atypical tumor cells for CD117. They reported that all 50 tumors in their study exhibited a similar pattern of mast cell staining with CD117 and tryptase, and subsequently proposed that the CD117-positive cells in AFX were mast cells, not neoplastic cells. Due to the rarity of positively staining tumor cells in their study they concluded, in contrast to recently published reports, including ours, that CD117 is neither a sensitive nor specific marker for identifying AFX.
Although we applaud the efforts of Beer and Haig to undertake further investigation into the utility or lack thereof for use of CD117 in the identification of AFX, it is important that previously published works are accurately referenced.
In our Letter to the Editor entitled “CD117 Immunoreactivity in Atypical Fibroxanthoma,” in the February 2009 issue, we reported that of our 14 cases of AFX, only 7 (50%) demonstrated positive staining in less than 10% of lesional cells. We noted that staining was seen only among the spindle cells constituting the neoplasm with none of the large, bizarre, or anaplastic cells. We felt it important to share these findings, as they were juxtaposed to the results of Mathew et al.1 Based on our results, in contrast to the previous report, we proposed that “these findings would suggest that CD117 does not seem to be a sensitive marker for AFX.”
We concluded that “as we strive to develop immunohistochemical techniques that allow for diagnostically reliable and reproducible results, it is clear that the findings of our study indicate that further investigation into the utility or lack thereof for CD117 in relationship to AFX is warranted.”2 Therefore, the conclusion of Beer and Haig's study supports our findings, rather than refutes them.
Keira L. Barr, MD*
*Departments of Dermatology and Pathology, University of California Davis Medical Center, Sacramento, CA
Jacqueline J. Russo, MD†
Vladimir Vincek, MD, PhD†
†Department of Pathology and Immunology, College of Medicine, University of Florida, Gainesville, FL
1. Mathew RA, Schlauder SM, Calder KB, et al. CD117 immunoreactivity in atypical fibroxanthoma. Am J Dermatopathol
2. Barr KL, Russo JJ, Vincek VV. CD117 immunoreactivity in atypical fibroxanthoma: letter. Am J Dermatopathol