Hello! Thank you for the query. If this lump comes from the anus or is attached to the verge of it, hemorrhoid is most possible reason. Itching is quite characteristic for hemorrhoids. It usually appears after a stool. Lump in perineum area can be also a sign of fistula between the skin and the rectum. In such case, lump gets painful and some discharge can appear. Other benign skin lesions like cyst or hair follicle inflammation are also possible. Please consult your doctor with this lump and the treatment depends of the diagnosis. Hope this will help. Regards.