The spleen is easily recognized by its alternating white and red pulps constituting the splenic pulp The white pulp stains purple and contains numerous lymphocytes (white blood cells) called splenocytes). The red pulp contains red blood cells. They are dispersed in splenic trabeculae seen easily on higher magnification.

Trabeculae  have veins within them called trabecular veins.

Differential diagnosis: The very compact organs like liver, pituitary gland and lymph nodes can be confused with spleen. Firstly liver has plates which radiate like the spoke of bicycle wheel, pituitary gland has cells which form cords rather than plates. Spleen has distinct red and white (blue) pulps and lymph nodes have distinct cortical nodules with light staining centers called germinal centers.

Ultrastructure
Histology
Embryology
Gross anatomy