Histopathological Subtypes and Clinical Presentation of Seborrheic Keratosis: A 15-Year Retrospective Analysis of 1,169 Cases in Hainan, China.

Seborrheic keratosis (SK), the most common benign epithelial tumor, frequently presents with cosmetic concerns despite its benign nature. The clinicopathological features of SK may demonstrate notable geographical variability. Diagnosis remains challenging due to varied clinical presentations. This study aimed to investigate the clinicopathological characteristics of SK through a comprehensive analysis of a large patient cohort. We conducted a retrospective analysis of clinical and pathological data from 1,169 patients diagnosed with SK between 1 January 2009 and 31 December 2023. Histopathological subtypes were categorized, and a descriptive analysis of demographic and clinical characteristics was performed. A total of 1,169 SK specimens were identified. The most frequent histopathological subtype was the acanthotic type (79.86%, 960 cases), followed by melanoacanthoma (7.98%, 92 cases), adenoid (5.32%, 64 cases), hyperkeratotic (4.90%, 59 cases), irritated (1.74%, 21 cases), and clonal (0.004%, 6 cases). The male-to-female ratio was 1.3:1, with a higher prevalence in men. SK most commonly affected the head, face, and neck, which accounted for 54.58% of cases (656/1,169), followed by the trunk (28.87%, 347 cases) and extremities (11.48%, 138 cases). The perineal area accounted for 4.48% (54 cases), while mucosal and plantar lesions were rare. The acanthotic subtype predominated across all anatomical sites, including mucosal and plantar regions. The age group most frequently diagnosed with SK was 40-59 years, with the acanthotic, melanoacanthoma, and adenoid types being particularly prevalent in this cohort. The clinical-pathological diagnostic concordance rate was 55.69%, indicating a relatively high rate of diagnostic discrepancy based on visual examination alone. Our study confirms the acanthotic subtype as the most common histological type of SK, predominantly observed in patients aged 40-59 years. The head, face, and neck emerged as the most frequently involved sites. Ultraviolet radiation may play a significant role in SK pathogenesis.