Spectrum of Tp53 gene mutation in basal cell carcinoma and its morphological subtypes in people of color.

Objectives: Basal cell carcinoma (BCC) is the most common cutaneous malignancy in white population. The pattern of exon specific p53 mutations in BCC and its subtypes remain undetected in our population. This study was designed to evaluate the prevalence and mutational spectrum of p53 mutations in basal cell carcinoma (BCC) and its subtypes in people of color in the population of Karachi, Pakistan. Study Design: Retrospective cross sectional study. Setting: Department of Pathology, Basic Medical Sciences Institute, Jinnah Post Graduate Medical Center Karachi, Pakistan. Period: Five-year study from January 2012 to December 2016. Material and Methods: Convenient sampling technique was used. Sample size was calculated using open EPI software. Analysis of 32 BCC cases for p53 gene mutations in exons 5-8 was detected by polymerase chain reaction technique. Sebaceous carcinoma and malignant melanoma were used as positive controls and normal skin was used as negative control. Results: Out of 32 BCC cases, 26 (81.2%) displayed p53 exon mutations. The number of cases with single exon mutation was 17 (65.3%). Exon 5 mutation was most frequently observed in 8 (30.7%) cases. This was followed by 5 (19.2%) cases with exon 6 mutation and 4 (15.3%) cases with exon 8 mutation. None of the cases revealed exon 7 mutation. A considerable number 9 (34.6%) of BCC displayed dual exon mutation.  Dual mutations of exon 6 & 8 were seen in 6 (23%) cases. Exon 5 & 7 mutation was noted in 2 (7.6%) cases followed by a single (3.8%) case with exon 6&7 mutation. The highest number 12 (46.1%) of single and dual exon mutations was recorded in nodular subtype of BCC. Conclusion: The current study confirms the expression of p53 gene mutation in BCC in colored population. Majority of the single mutations were observed in exon 5. Dual exon mutation was the most notable finding of this study. The highest number of single and dual exon mutations was recorded in nodular form of BCC.