Actinic keratosis

Criteria based on keratinocyte intraepidermal neoplasia[28]Fu W, Cockerell CJ. The actinic (solar) keratosis: a 21st-century perspective. Arch Dermatol. 2003 Jan;139(1):66-70. http://www.ncbi.nlm.nih.gov/pubmed/12533168?tool=bestpractice.com [75]Yantsos VA, Conrad N, Zabawski E, et al. Incipient intraepidermal cutaneous squamous cell carcinoma: a proposal for reclassifying and grading solar (actinic) keratoses. Semin Cutan Med Surg. 1999 Mar;18(1):3-14. http://www.ncbi.nlm.nih.gov/pubmed/10188837?tool=bestpractice.com

There are no standard, widely accepted grading criteria. A grading system called keratinocyte intraepidermal neoplasia (KIN) divides AK lesions as follows, but has been criticized several times in the literature and is not widely accepted.[76]Carag HR, Prieto VG, Yballe LS, et al. Utility of step sections: demonstration of additional pathological findings in biopsy samples initially diagnosed as actinic keratosis. Arch Dermatol. 2000 Apr;136(4):471-5. https://archderm.jamanetwork.com/article.aspx?articleid=190138 http://www.ncbi.nlm.nih.gov/pubmed/10768645?tool=bestpractice.com [77]Scurry J. Grading of actinic keratoses. J Am Acad Dermatol. 2001 Jun;44(6):1052-3. http://www.ncbi.nlm.nih.gov/pubmed/11369925?tool=bestpractice.com

KIN I

• Clinical: undetectable or flat, pink macule or patch on solar-damaged skin; background mottling; no roughness or hyperkeratosis

• Histologic: focal atypia of basal keratinocytes of lower one third of the epidermis.

KIN IIa

• Clinical: pink to red papule or plaque with rough, hyperkeratotic surface; minimal induration.

• Histologic: focal atypia of keratinocytes of the lower two-thirds of the epidermis; alternating ortho- and parakeratosis with sparing of acrotrichia.

KIN IIb

• Clinical: similar to IIa but more induration, more hyperkeratosis, and/or more erythema; all KIN lesions (other than KIN III) on lip and conjunctiva.

• Histologic: focal atypia of keratinocytes of at least the lower two-thirds of the epidermis; focal hyperkeratosis, often greater than IIa; 1 or more additional features such as acantholysis, involvement of adnexal structures, prominent acanthosis, and buds of keratinocytes into the upper papillary dermis present.

KIN III

• Clinical: red, scaly, indurated plaques on sun-damaged skin; may be pigmented; seen on other sites such as mucosa in bowenoid papulosis and erythroplasia of Queyrat.

• Histologic: diffuse atypical keratinocytic proliferation involving the full thickness of the epidermis; parakeratosis, acanthosis, papillomatosis, involvement of adnexal structures.