Adenocarcinoma Low grade, please explain the condition

My dad had done the colonoscopy last week in that biopsy result as follows:
SPECIMEN : Growth sigmoid Colon
GROSS : Pale white 3 mm nodules enbedded in toto .
MICROSCOPIC : Sections show an invasive adenocarcinoma The tumour cells infiltrate muscularis
DIAGNOSIS : muccsa , sigmoid colon , Biopsy Adenocarcinoma LOw grade .

can you please explain the condition and preferred way of diagnosis