1) Acute Peptic Ulcer :-
Grossly – Acute ulcers are multiple. They are more common anywhere in the stomach decreasing frequently in the first part of duodenum. They may be oval or circular in shape.

Microscopically – They are shallow, do not invade the muscular layer. Margin & base show inflammatory reactions. These commonly heal by re-epithelialisation without leaving any scars.

2) Chronic Peptic Ulcer :-
Grossly – Grossly gastric & duodenal ulcers are similar. Ulcers are commonly solitary, small (1-1.25cm in diameter), round to oval & characteristically ‘punched out’. Ulcers may very in depth from being superficial to deep ulcers (mucosa to muscular layer).
Mostly are benign <1% can turn into malignant form which are larger ,bowl shaped with elevated mucosa at margins. Gastric ulcer are found along the lesser curvature in the region of pyloric antrum & duodenal ulcer are found in the first part of the duodenum (post pyloric).

Microscopically –Have 4 histological zones, from within outside :-
Necrotic Zone :- Lies in the floor of the ulcer & composed of fibrous exudates containing necrotic debris.
Superficial exudative zone :- lies underneath of necrotic zone. Tissue elements show coagulative necrosis giving eosinophillic, smudgy (dirty        mark) appearance.
Granulation tissue Zone :- Merging into necrotic zone, composed of nonspecific inflammatory infiltrate.
Zone of cicatrisation :- It is merging into thick layer of granulation tissue composed of dense fibrocollagenic scar. Thrombosed arteries may cross the ulcer which on erosion may result in haemorrhage.