Pathology and pathobiology of actinic (solar) keratosis - an update.Br J Dermatol. 2007 Dec;157 Suppl 2:18-20.

Actinic keratosis is a UV light-induced lesion and develops mostly in fair-skinned patients being susceptible to solar damage. The term actinic keratosis (AK) describes clinically ill-defined reddish to reddish-brown scaly lesions on erythematous base in areas damaged severely by sunlight. The term does not imply anything about the biology or histopathology. Actinic keratoses (AKs) have been recognized as precursor of cancer or of precancerous lesions in the past but today they are considered as an early in situ squamous cell carcinoma (1,2) and are categorized in several classifications with subdivisions into three grades depending on the amount of atypical keratinocytes in the epidermis.(3-6) The incidence of development of AK in caucasians increases with age, proximity to the equator and outdoor occupation. Australia has the highest skin cancer rate in the world. AKs are discovered in up to 40-50% of the Australian population older than 40 years.(7) AKs are the most common malignant lesion of the skin.(8-12).

Cytological diagnosis of basal cell carcinoma and actinic keratosis, using Papanicolaou and May-Grünwald-Giemsa stained cutaneous tissue smear.Cytopathology. 2007 Oct 4.

Objective: Cytology may become the diagnostic method of choice with the advent of new non-invasive treatments for non-melanoma skin cancer, as the sampling technique for cytology entails little tissue disfiguration. The aim of this study was to compare and evaluate the diagnostic performance of scrape cytology using two different cytological staining techniques, and to evaluate additional touch imprint cytology, with that of histopathology of basal cell carcinoma (BCC) and actinic keratosis (AK). Methods: We investigated 50 BCC and 28 AK histologically verified lesions, from 41 and 25 patients, respectively. Two separate skin scrape samples and one touch imprint sample were taken from each lesion. The smears were stained with Papanicolaou (Pap) or May-Grünwald-Giemsa (MGG) stains. All cytological specimens were examined in random order by pathologists without knowledge of the histology. Cytodiagnostic results were compared with the histopathological report. Results: Scrape cytodiagnosis agreed with histopathology in 48 (Pap) and 47 (MGG) of the 50 BCC cases, and in 26 of 28 (Pap) and 21 of 26 (MGG) AK cases, yielding sensitivities of 96%, 94%, 93% and 81%, respectively. No significant difference in sensitivity between the two staining methods was found but a trend towards higher Pap sensitivity for AK was noted (P = 0.10). Touch imprint cytology confirmed histopathology in 38 of the 77 cases of BCC and AK. Conclusion: Cytological diagnosis with either Pap or MGG stain for BCC and AK is reliable, and differentiates well between BCC and AK. Imprint cytology proved to be non-diagnostic in half of the examined cases.