[460] Factor XIIIa Is a Highly Sensitive Nuclear Marker of Sebaceous Differentiation in Normal and Neoplastic Sebocytes

Lindsey N Clark, Hillary R Elwood, Sara C Shalin, Bruce R Smoller, Jerad M Gardner. University of Arkansas for Medical Sciences, Little Rock, AR

Background: Sebaceous proliferations are commonly encountered cutaneous lesions. Some of these, especially sebaceous carcinoma, can be easily confused with other cutaneous neoplasms, particularly poorly differentiated squamous cell carcinoma. Few useful or specific immunohistochemical markers for sebaceous differentiation are available. We incidentally observed strong nuclear expression in sebaceous glands by Factor XIIIa, and we hypothesized that this antibody may be a useful marker in sebaceous proliferations including sebaceous carcinoma.
Design: Our archive files were searched for sebaceous proliferations including sebaceous hyperplasia, sebaceous adenoma, sebaceoma and sebaceous carcinoma. Immunohistochemistry for Factor XIIIa was performed according to the manufacturer's guidelines. All cases were reviewed by four separate pathologists for accuracy of diagnosis, and the presence and intensity of staining. Immunostaining distribution was scored as diffuse, focal or absent nuclear positivity while intensity was scored as strongly positive, weakly positive or negative. Normal sebaceous glands and/or dermal dendritic cells in each case were used as controls.
Results: Our series included 27 representative cases of sebaceous proliferation as follows: 7 sebaceous hyperplasias, 8 sebaceous adenomas, 5 sebaceomas, 7 sebaceous carcinomas. Factor XIIIa expression was present in all normal background sebaceous glands and in 100% of sebaceous proliferations with the following scores: sebaceous hyperplasia – 100% strong/diffuse; sebaceous adenoma – 100% strong/diffuse; sebaceoma – 60% strong/diffuse, 20% strong/focal, 20% weak/focal; sebaceous carcinoma – 71% strong/diffuse, 29% strong/focal. Additionally, distribution and intensity of expression seemed to directly correlate with increased maturation of the sebocytes; thus, basaloid cells were typically negative and mature sebocytes were strongly/diffusely positive for Factor XIIIa. A small number (n=6) of poorly differentiated squamous cell carcinomas were also stained for Factor XIIIa; all showed either negative or weak/focal nuclear expression.
Conclusions: We report the novel finding of consistent nuclear expression of Factor XIIIa in normal, hyperplastic, and neoplastic sebocytes. From our pilot series, Factor XIIIa appears to be a highly sensitive marker of sebaceous differentiation. Our preliminary data examining a small number of squamous cell carcinomas suggests Factor XIIIa may have clinical utility as a specific marker to distinguish sebaceous carcinoma from poorly differentiated squamous cell carcinoma.
Category: Dermatopathology

Wednesday, March 6, 2013 9:30 AM

Poster Session V # 65, Wednesday Morning


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