Can anyone explain what a lobule is?

Breast profile:

A ducts

B lobules

C dilated section of duct to hold milk

D nipple

E fat

F pectoralis major muscle

G chest wall/rib cage

Enlargement:

A normal duct cells

B basement membrane

C lumen (center of duct)

http://www.breastcancer.org/pictures/breast_anatomy/image_1.jsp

Lobes, Lobules and Breast Cancer Each breast is composed of up to 20 sections called "lobes." Each lobe is made up of many smaller "lobules," where milk is made. Lobes and lobules are connected by small tubes called "ducts" that can carry milk to the nipple.   http://www.womenshealthzone.net/cancer/breast-cancer/lobes-lobules/

The picture is a bit misleading as far as the location of the lobules.  They aren't all nested around the pectoralis muscles.  Lobules are in many places in the breast, including just underneath the areola. The ducts are not semi-straight tubes; ducts often twist and turn, much like a sagebrush.  Ducts may branch, but they don't normally intersect.

I doubt if you'd be able to feel a solitary lobule.

Normal, sexually mature breast showed an average lobular surface of 0.23 sq mm http://www.ncbi.nlm.nih.gov/pubmed/7301774

Most breast lumps are either the benign fibroadenomas or the almost always benign cyst (fluid filled sac).  Overall, if you lump all age groups together, about 80% of breast biopsies turn out to be benign.  If you are post-menopausal and have a breast lump,you have a somewhat greater chance that breast lumps are cancerous.