**Abstract**

Due to our environmental change, neoplasia is much more common worldwide. And nowadays some well-developed modalities of cancer diagnosis are available. That is why we have to learn about neoplasia. Neoplasia is defined as a genetic disorientation of cell growth that is triggered by acquired or less commonly inherited mutations affecting a single cell and its clonal progeny. Nonlethal genetic damage lies at the heart of carcinogenesis. Genetic damage may be acquired or inherited. Mainly four types of cellular genes are involved in molecular carcinogenesis: 1. Growth-promoting protooncogenes, 2. Growth-inhibiting tumor suppressor genes, 3. Genes that regulate apoptosis, and 4. Genes involved in DNA repair. Carcinogenesis is a multistep process. Each cancer must result from accumulation of multiple mutations. Besides this carcinogens like chemicals, microbial and radiation can cause genetic damage or mutations that initiate cancer. Initiation of carcinogenesis is started with mutations and promotion of tumor growth is in involved cell. Due to the advanced tumor diagnosis, it helps in early tumor detection. We can identify a malignant cell by cell criteria. This property helps us to treat cancer early and help us to cure it. Therefore, nowadays tumor pathology or neoplasia is a topic of the time.

**Keywords:** neoplasia, definition, classifications, epidemiology of cancer, molecular basis of cancer, Warburg effect, invasion and metastasis, chemical and radiation carcinogenesis, microbial carcinogenesis, lab diagnosis, tumor marker, paraneoplastic syndrome, tumor staging
