What is the main type of inheritance found in HNPCC, and what is its primary cancer feature?

Hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome, is primarily characterized by autosomal dominant inheritance. This means that an individual only needs one mutated copy of a gene associated with the syndrome to develop the condition. In HNPCC, the genes usually involved are mismatch repair (MMR) genes, such as MLH1, MSH2, MSH6, and PMS2. Because the inheritance is autosomal dominant, individuals with a family history of HNPCC have a significantly increased risk of developing colorectal cancer and other associated malignancies.

The primary cancer feature of HNPCC is the tendency for right-sided colon cancers, which are typically characterized by a different histological pattern compared to left-sided cancers often seen in sporadic cases. Right-sided colon cancers tend to arise in the proximal colon and are generally more poorly differentiated. Unlike familial adenomatous polyposis (FAP), patients with HNPCC develop colorectal cancers without an abundance of polyps, making it distinct in presentation.

Thus, the notion that HNPCC is linked to autosomal dominant inheritance and is characterized by right-sided colon cancers without polyposis is fundamentally accurate and aligns with the understanding of this genetic condition.