Multi-Region Sequence Analysis of a Pregnancy-Related Oral Squamous Cell Carcinoma Exhibiting Low-Level Aggressive Behavior.

We analyzed the genetic and epigenetic profiles of an oral squamous cell carcinoma affecting a 41-year-old pregnant female. The patient presented with an oral mass located at the hard and soft palate with bone involvement and lymph node metastases (T4N1M0). She had been treated with multimodal radiotherapy and chemotherapy, and she is currently alive with no evidence of disease 8 years after treatment. DNA methylation and DNA mutation analyses were used to analyze multiple samples from the tumor mass and from the non-neoplastic mucosa to verify tumor heterogeneity. Genetic and epigenetic analyses revealed the presence of one shared TP53 driver mutation with the same DNA methylation profile in each of the 3 areas of the tumor mass; only 2 additional passenger mutations were detected, suggesting a simple clonal homogeneous carcinoma, which usually is associated with low-level aggressive behavior. Additionally, no genetic or epigenetic alteration in the non-neoplastic oral mucosa was detected, demonstrating the absence of field cancerization. The low aggressiveness of the lesion was confirmed by the patient being free of disease at a long-term follow-up examination. These data suggest a different molecular transformation pathway in pregnancy-related oral squamous cell carcinomas, providing new perspectives for further investigation.