We report a case of a 60-year-old woman with a 4-year history of an asymptomatic plaque on her left cheek. The lesion was composed of two distinct adjacent and continuous parts comprising a lateral yellowish flat portion and a medial reddish nodular portion. Histologic examination revealed that the plaque was composed of two different adjacent tumors. The lateral portion of the plaque had the aspect of a seborrheic keratosis (SK) with hyperkeratosis and acanthosis with irregular proliferation of apparently benign basaloid and squamous keratinocytes and small horn pseudocysts. The medial portion showed a dermal tumor made up of differently sized lobules composed of immature sebocytes mixed with single or clustered mature sebaceous cells. Sebaceous ductal differentiation was visible. We made the diagnosis of SK associated with sebaceoma. The association of an SK with a benign neoplasm with sebaceous differentiation is rare. It may only be a coincidence, but a role for the preexisting SK cannot be ruled out.
- Collision tumor
- Seborrheic keratosis
ASJC Scopus subject areas
- Pathology and Forensic Medicine