Clinical and Histopathological Investigation of Seborrheic Keratosis

BACKGROUND Seborrheic keratosis (SK) is one of the most common epidermal tumors of the skin. However, only a few large-scale clinicohistopathological investigations have been conducted on SK or on the possible correlation between histopathological SK subtype and location. OBJECTIVE The aim of this study was to analyze the clinical and histopathological features of a relatively large number of cases of diagnosed SK. METHODS Two hundred and seventy-one pathology slides of skin tissue from patients with clinically diagnosed SK and 206 cases of biopsy-proven SK were analyzed. The biopsy-proven cases of SK were assessed for histopathological subclassification. The demographic, clinical, and histopathological data of the patients were collected for analysis of associated factors. RESULTS The most frequent histopathological subtype was the acanthotic type, followed by mixed, hyperkeratotic, melanoacanthoma, clonal, irritated, and adenoid types; an unexpectedly high percentage (9.2%) of the melanoacanthoma variant was observed. The adenoid type was more common in sun-exposed sites than in sun-protected sites (p=0.028). Premalignant and malignant entities together represented almost one-quarter (24.2%) of the clinicopathological mismatch cases (i.e., mismatch between the clinical and histopathological diagnoses). Regarding the location of SK development, the frequency of mismatch for the sun-exposed areas was significantly higher than that for sun-protected areas (p=0.043). CONCLUSION The adenoid type was more common in sun-exposed sites. Biopsy sampling should be performed for lesions situated in sun-exposed areas to exclude other premalignant or malignant diseases.