**Core Concept**
Ulcer with undermined edges is a classic histopathological and clinical feature of tubercular ulcers, which result from chronic infection and tissue destruction by *Mycobacterium tuberculosis*. This type of ulcer is characterized by a well-demarcated, irregular border with undermined edges due to the slow, progressive nature of the infection and granulomatous tissue destruction.

**Why the Correct Answer is Right**
Tubercular ulcers typically present with undermined, rolled, and irregular edges due to the destructive action of granulomas and caseous necrosis in the tissue. The infection causes chronic inflammation and tissue breakdown, leading to a "punched-out" appearance with well-defined, undermined borders. This is distinct from other ulcers like malignant (which have irregular, ragged edges) or venous (which have a well-demarcated, convex base and poor healing). The presence of undermined edges is highly suggestive of tuberculosis, especially in endemic areas or patients with a history of exposure.

**Why Each Wrong Option is Incorrect**
Option A: Malignant ulcers have ragged, irregular, and poorly defined edges with infiltrative growth, not undermined borders.
Option C: Venous ulcers have a convex, well-demarcated base, with a pale, edematous appearance and are usually found in dependent areas.
Option D: Diabetic ulcers typically have a shallow, punched-out appearance with a granular base and are often located on the plantar surface; they do not show prominent undermining.

**Clinical Pearl / High-Yield Fact**
Remember: "Undermined edges = Tubercular ulcer." This is a key diagnostic clue in the differential diagnosis of chronic ulcers, especially in patients with a history of exposure or chronic infection.

✓ Correct Answer: B. Tubercular ulcer