Seborrhoeic keratosis and malignancy: collision tumour or malignant transformation?

Area of Science:

• Dermatopathology
• Oncology
• Histopathology

Background:

• Seborrhoeic keratoses are common benign skin neoplasms.
• The association between seborrhoeic keratoses and non-melanoma skin cancer is not well-established.
• Distinguishing between benign seborrhoeic keratoses and malignant lesions can be challenging clinically.

Purpose of the Study:

• To investigate the incidence and types of non-melanoma skin cancer associated with seborrhoeic keratoses.
• To determine if malignant changes arise within seborrhoeic keratoses or represent collision tumors.
• To evaluate clinical diagnostic accuracy for these associated lesions.

Main Methods:

• Retrospective analysis of 813 histological specimens reported as seborrhoeic keratoses.
• Identification and classification of any co-existing non-melanoma skin cancers.
• Comparison of histological findings with clinical diagnoses.

Main Results:

• 43 (5.3%) specimens showed associated non-melanoma skin cancer.
• Intraepidermal carcinoma (squamous cell carcinoma in situ) was most common (36 cases).
• 28 lesions suggested malignant transformation within seborrhoeic keratoses, predominantly on the head; 12 showed adjacent dual pathologies, often on the trunk/limbs.

Conclusions:

• A significant proportion of seborrhoeic keratoses harbor non-melanoma skin cancer, potentially through malignant transformation or collision.
• Clinical diagnosis can be unreliable for these associated lesions.
• Further investigation into the pathogenesis and clinical management of these dual-pathology lesions is warranted.