Polyclonality of Multiple Sporadic Basal Cell Carcinomas

Development of Multiple-Lesion Basal Cell Carcinoma of the Skin: A Comprehensive Review

An interesting clinical feature of basal cell carcinoma (BCC) of the skin is a marked variation in tumor number, sites, and accrual. Some individuals develop only a single BCC lesion with no impact on health status, while a significant proportion is affected repeatedly with new primary tumors at various body sites. Approximately 29% of patients with a first BCC will develop at least 1 more lesion during their lifetime. The candidate predictors for multiple BCC development include younger age and a superficial BCC subtype at the time of the first diagnosis, red hair phenotype, initial or frequent tumor location on the trunk or on the upper limbs, and male gender. The pathogenesis of multiple BCC development does not seem to be related to greater UVR exposure. Individual genetic susceptibility may have a greater impact than extrinsic factors. In clinical practice, it is meaningful to estimate the probability of new BCC development in patients who have an initial lesion. A reliable prediction model for individualized risk stratification remains a subject of continued research; however, a focus on the risk factor profile is beneficial for clinical screening and may help clinicians to determine the individuals who should be followed up more closely.

Clonal architecture of human prostatic epithelium in benign and malignant conditions

The location of stem cells in the epithelium of the prostatic acinus remains uncertain, as does the cellular origin of prostatic neoplasia. Here, we apply lineage tracing to visualize the clonal progeny of stem cells in benign and malignant human prostates and understand the clonal architecture of this epithelium. Cells deficient for the mitochondrially-encoded enzyme cytochrome c oxidase (CCO) were identified in 27 frozen prostatectomy specimens using dual colour enzyme histochemistry and individual CCO-normal and -deficient cell areas were laser-capture microdissected. PCR-sequencing of the entire mitochondrial genome (mtDNA) of cells from CCO-deficient areas found to share mtDNA mutations not present in adjacent CCO-normal cells, thus proving a clonal origin. Immunohistochemistry was performed to visualize the three cell lineages normally present in the prostatic epithelium. Entire CCO-deficient acini, and part-deficient acini were found. Deficient patches spanned either basal or luminal cells, but sometimes also both epithelial cell types in normal, hyperplastic or atrophic epithelium, and prostatic intraepithelial neoplasia (PIN). Patches comprising both PIN and invasive cancer were observed. Each cell area within a CCO-deficient patch contained an identical mtDNA mutation, defining the patch as a clonal unit. CCO-deficient patches in benign epithelium contained basal, luminal and endocrine cells, demonstrating multilineage differentiation and therefore the presence of a stem cell. Our results demonstrate that the normal, atrophic, hypertrophic and atypical (PIN) epithelium of human prostate contains stem cell-derived clonal units that actively replenish the epithelium during ageing. These deficient areas usually included the basal compartment indicating the basal layer as the location of the stem cell. Importantly, single clonal units comprised both PIN and invasive cancer, supporting PIN as the pre-invasive lesion for prostate cancer.