Slide 140.Keratoacanthoma, Skin

A. Brief Descriptions

    1. Rapidly developing neoplasm.

    2. Sun exposed skin of whites older than 50 years.

    3. Flesh-colored, dome-shaped nodules with a central keratin-filled plug. (crater-like)

 B. Gross Findings

  1. Begins as a firm, round, flesh colored or red papule later forming a central crater filled with keratin

C. Micro Findings

  1. Large, central keratin-filled crater.

  2. The epidermis extends like a lip over the sides of the crater.

  3. At the base of the crater, irregular epidermis proliferation extend both upward into the crater and downward from the base of the crater.

  4. In more centrally of the epidermal proliferation large squamoid cells have a characteristic homogenous and pale-pink (" glassy ") cytoplasm; at the periphery, the cells are basaloid.

  5. There are many horn pearls, most of which shows complete keratinization in their center.

  6. The base of fully developed keratoacanthoma appears regular and well demarcated.

  7. Rather dense inflammatory infiltrate is present at the base of the lesion.

D. Others

  1. Benign but rapidly growing tumor

  2. Predilection site: central face

  3. Age: at or after middle age

E. Reference

  1. Robbins Pathologic Basis of Disease. Ch27. p.1181



Fig. 140-1 (4x)





Fig. 140-2 (10X)





Fig. 140-3 (20X)





Fig. 140-3 (20X)




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Fig. 140-7 (40X)