Desmoplastic trichilemmoma of the facial region mimicking invasive carcinoma

Upstaging of basal cell and squamous cell carcinomas during definitive surgery: a review of predictive preoperative clinical and histologic features

The incidence of nonmelanoma skin cancer (NMSC) in the United States is increasing with approximately 3.6 million cases diagnosed per year. The staging and treatment of NMSC is guided by histologic subtype based on skin biopsy, along with other tumor-specific factors. However, a biopsy only represents a portion of the tumor, so there is a risk of upstaging at the time of definitive surgery. We conducted a review of the literature and found that a significant proportion of NMSC were upstaged during surgery. The rate of upstaging of basal cell carcinoma (BCC) was 7-31% and that of squamous cell carcinoma in situ (SCCIS) to squamous cell carcinoma (SCC) was 3-39%. Biopsy sampling error and variability in interpreting and reporting by dermatopathologists contribute to these discrepancies. It is pertinent to consider more comprehensive treatment modalities for tumors at high risk for upstaging. Diligence to identify tumors at higher risk for upstaging will allow clinicians to optimize management.

CD34 and BerEP4 Are Helpful to Distinguish Basaloid Tricholemmoma From Basal Cell Carcinoma

Tricholemmoma, a benign follicular neoplasm with outer root sheath differentiation, typically comprises clear or pale cells, and when multiple is pathognomic of Cowden's syndrome. The tumor is probably underrecognized and in basaloid examples can be difficult to distinguish from basal cell carcinoma (BCC). We studied 55 tricholemmomas (including 15 basaloid cases) and compared immunohistochemical profile with nodular BCC from our archives. Basaloid and non-basaloid tricholemmomas had similar staining characteristics. BerEP4 was focally positive (range 10%-20%) in only 3/39 (7.7%) tricholemmomas compared with widespread positivity in BCC (90.8%, 139 of 151 cases with ≥50% tumor area stained). CD34 was expressed, usually focally (median 20%, range 10%-90%), in 52/53 (98.1%) tricholemmomas and was negative in all 21 BCCs stained. EMA staining lacked sensitivity or specificity in differentiating tricholemmoma from BCC. Five or more Merkel cells were found in 7/17 (40.1%) tricholemmomas and 1/23 (4.3%) nodular BCCs studied. In summary, immunohistochemistry is helpful in distinction between tricholemmoma, including difficult basaloid examples (BerEP4 negative or focal, CD34 positive) compared with BCC (BerEP4 widespread in most cases, CD34 negative). The presence of 5 or more Merkel cells is a relatively specific but not a particularly sensitive discriminator.