Histology Course S XII 1 Department of Pathology, University of Zurich Histology Course

S XII 1 seborrheic keratosis of the skin HE  
  ICD-10: L82

61-year-old male with pigmentation on back (mole?)

- Skin spindle with central, well demarcated, homogenous dark brown lesion, 6 mm in diameter
- Well demarcated edges and good dermoepidermal demarcation, no signs of infiltration of the dermis.
- Proliferation of basal-cell-like cells
- There is no pathological polymorphism of the cells and nuclei, the nuclei are unremarkable.
- Keratin inclusions can be seen.
- Distinct pigmentation in some areas.

Comment: The mitotic activity can be markedly elevated especially in inflamed seborrheic keratoses but there are no atypical mitoses. Seborrheic keratoses are often clinically diagnosed as nevi due to the pigmentation.