Malignant Transformation in Sinonasal Papillomas Is Closely Associated With Aberrant p53 Expression.

Background: Sinonasal papillomas are generally benign lesions that arise from the lining of the nasal or paranasal sinuses. Occasionally, however, they may undergo malignant change, an event that is poorly understood. To elucidate the possible molecular basis of this transformation, a series of these lesions were examined for abnormal p53 protein expression and for mutations in the genes of exons 5-8. Methods and Results: Eleven cases of sinonasal papillomas (seven with associated carcinoma) were analyzed immunohistochemically for overexpression of p53 protein, as were three cases of squamous carcinoma. Genetic analysis of exons 5-8 was performed via topographic genotyping of representative tissue and polymerase chain reaction amplification. All seven papillomas with associated carcinoma showed evidence of aberrant function of the p53 gene, as did the three squamous cell carcinomas. Several exhibited point mutations resulting in missense codons. One case possessed a nonsense mutation and was immunonegative. Conclusions: p53 gene mutation appears to be closely associated with malignant transformation in sinonasal papillomas, and genotyping of archival tissues is useful in the evaluation of malignant or potentially malignant lesions.

Microdissection-Based p53 Genotyping: Concepts for Molecular Testing.

p53 is the most commonly altered tumor-suppressor gene in humans, involved in the development and progression of many diverse forms of human cancer. Although much remains to be learned about the biology of this important growth regulatory gene, sufficient experience has been accumulated with respect to the occurrence and pattern of p53 mutational change to justify molecular diagnostic testing for specific objectives. The authors outline specific concepts for testing with particular emphasis for solid tumor molecular diagnostics. This article focuses on microdissection-based fixed tissue molecular analysis, introducing new considerations related to quality control appropriate for this type of methodology. Given the rapidly evolving nature of molecular genetics, the suggestions provided here should be viewed as flexible. Nevertheless, the concepts are intended to serve as a model for other oncogene/tumor suppressor-gene assays to be developed with the overall purpose of establishing informative integrated histopathologic/genetic molecular diagnostic testing to complement standard microscopic analysis.

Prediction of Biologic Aggressiveness in Colorectal Cancer by p53/K-ras-2 Topographic Genotyping.

Background: Topographic genotyping is a system of solid tissue molecular analysis designed to correlate microscopic alterations with specific forms of gene damage. In this system, microscopic targets are selected on the basis of cellular and immunohistochemical features. Minute tissue samples corresponding to these targets are precisely removed and analyzed for the presence and specific type of oncogene/tumor suppressor gene damage by means of polymerase chain reaction (PCR) followed by DNA sequencing. In this study, topographic genotyping was used to investigate the prognostic value of p53 and K-ras-2 mutational damage in 204 patients with colorectal cancer from two tertiary care centers. Methods and Results: The intensity and distribution of p53 immunohistochemical staining were correlated with the presence and specific type of mutational change, which resulted in a better understanding of the highly variable nature of p53 immunostaining patterns. Molecular genotype was correlated with the depth and extent of colorectal cancer spread (Dukes B and C) and with survival for follow-up periods of up to 10 years. An algorithm for p53/K-ras-2 genotyping was formulated to include p53 immunohistochemistry and DNA sequencing both of p53 exons 5-8 and of K-ras-2 exons 1 and 2. By using this algorithm, survival was shown to be significantly better in those patients whose tumors manifested normal p53 and K-ras-2 genes (P >.01). Patients with p53-mutated tumors composed a poor prognostic group, characterized by a high rate of intra-abdominal recurrence in the form of peritoneal seeding. Patients with K-ras-2-mutated tumors also composed a poor prognostic group, marked by a tendency for distant hematogenous metastasis involving lung, bone, and brain. Conclusions: Topographic genotyping's molecular diagnostic approach to colorectal cancer combines immunohistochemistry, PCR, and DNA sequencing. It is informative, cost-effective, timely, and yet fully integrated with standard histopathology. The use of this approach by pathologists as a model system for molecular diagnosis of colorectal cancer and other forms of solid tumor malignancy is recommended. As new prognostic molecular lesions are documented for tumor progression and metastasis, topographic genotyping will be well suited to facilitate their clinical application.

Relationship of p53 Genotype to Second-look Recurrence and Survival in Ovarian Epithelial Malignancy.

Background: Clinical stage at presentation and tumor status at second-look laparotomy are currently the best predictors of patient survival in epithelial ovarian carcinoma (EOC). Methods and Results: To evaluate the predictive value of genetic analysis, the presence and type of p53 mutation (p53 genotype) was determined in 76 patients treated for EOC between 1987 and 1992 and subjected to second-look laparotomy following initial treatment. Mutational analysis of p53 was performed retrospectively by means of topographic genotyping (TG), using formalin-fixed, paraffin-embedded tissue of the primary and recurrent tumor. In TG, minute tissue samples were dissected from unstained histologic sections, amplified for p53 exons 5-8 with the polymerase chain reaction (PCR), and then direct sequenced. The p53 genotype was correlated with tumor stage, histologic grade and type, tumor status at second look, and survival at 3 and 5 years. Mutational change involving p53 exons 5-8 was found in 41 of 76 tumors (54%), consisting of 29 cases manifesting missense alterations and 12 cases having truncations (deletions, insertions, or stop codons). Tumor mutational change for each patient was strictly limited to a single type, being identical in all recurrences of an individual primary cancer. Mutations of p53 were distributed over exons 5-8, with certain "hot spots" being evident (codons 220, 245, and 273). Mutational change was present in all stages of primary EOC, but was relatively more frequent in tumors of advanced stage (III and IV). Epithelial ovarian carcinoma manifesting p53 mutational damage was significantly more likely to show recurrence at second-look laparotomy (P <.001) and to have shorter survival at the 3- and 5-year follow-up (P <.001) evaluation. The predictive value of p53 genotype was independent of stage at presentation, histologic grade, or histopathologic type. Conclusions: Genotyping of p53 provides useful information on tumor aggressiveness and is an informative predictive marker of biologic tumor behavior, treatment response, and survival in EOC.