Abstract

Background: SPARC (secreted protein acidic and rich in cysteine) is a key player in the stromal remodeling associated with invasive carcinomas, and its detection by immunohistochemistry may prove diagnostically useful in detecting invasion. The present study explores stromal SPARC expression patterns in invasive mucocutaneous squamous cell carcinoma (SCC). The patterns are then compared to those of SMA, a relatively well-studied but imperfect marker of cancer-associated stroma.

Methods: Nineteen cases of infiltrating keratinizing SCCs from skin and mucous membranes were assessed semi-quantitatively for immunoreactivity with anti-SMA or anti-SPARC antibodies in tumor-free and tumor-associated stroma.

Results: All cases of invasive SCCs (n=19) demonstrated stromal expression of both SMA and SPARC. However, SPARC showed more diffuse reactivity than SMA, with SPARC demonstrating a mean percentage reactivity range of 50-75%, versus 25-50% for SMA. In tumor-free stroma, SMA was negative in all cases, whereas SPARC was positive in up to 5% of dendritic stromal cells in more than half of the cases.

Conclusions: Stromal SPARC overexpression is a consistent finding in invasive SCC, and SPARC is more sensitive but less specific for cancer-associated stroma than SMA. While H&E examination remains the gold standard for determining whether invasion is present, stromal SPARC expression patterns may serve as an adjunct to the histopathologic impression.

Keywords: SPARC; SMA; Stroma; Squamous cell carcinoma; Invasion