Morphologic Mimickers of Seborrheic Keratoses: Cutaneous Lesions Masquerading as Seborrheic Keratoses.

Seborrheic keratosis is an epithelial-derived benign neoplasm, which presents as a solitary tumor or multiple lesions. It is an acquired skin tumor that is frequently observed in older individuals. Benign neoplasms, as well as premalignant or malignant tumors, can mimic the clinical appearance of a seborrheic keratosis. A man presented with a chronic lesion on his abdomen that had changed in the color and size. The suspected diagnosis was a seborrheic keratosis. However, the microscopic evaluation of a biopsy tissue specimen established a diagnosis of a pigmented squamous cell carcinoma in situ. In addition to squamous cell carcinoma in situ and squamous cell carcinoma, other malignant tumors, premalignant lesions, and benign lesions can mimic a seborrheic keratosis. If a patient presents with a presumptive seborrheic keratosis that has changed in appearance and for which malignancy is also suspected, a biopsy may be helpful for diagnostic clarification to either confirm that the lesion is indeed a seborrheic keratosis or to establish the diagnosis of the lesion that mimics a seborrheic keratosis.