Malpighian layer
The Malpighian layer (stratum mucosum or stratum malpighii) of the epidermis is generally defined as both the stratum basale (basal layer) and the thicker stratum spinosum (spinous layer/prickle cell layer) immediately above it as a single unit,<ref name="Rooks">McGrath, J.A.; Eady, R.A.; Pope, F.M. (2004). Rook's Textbook of Dermatology (Seventh Edition). Blackwell Publishing. Pages 3.1-3.6. Template:ISBN.</ref><ref>TheFreeDictionary > Malpighian layer Citing: *Saunders Comprehensive Veterinary Dictionary, 3 ed. 2007</ref> although it is occasionally defined as the stratum basale specifically,<ref>TheFreeDictionary > Malpighian layer Citing: *The American Heritage Medical Dictionary 2007</ref> or the stratum spinosum specifically.<ref>Template:Cite book</ref>
It is named after the Italian biologist and physician Marcello Malpighi.
Basal cell carcinoma originates from the basal layer of the stratum malpighii.
This layer is where almost all of the mitotic activity in the epidermis occurs. The activity of these cells is increased by IL-1 (interleukin-1) and epidermal growth factor. The activity is decreased by transforming growth factor beta.<ref>Mescher, A. L., Mescher, A. L., & Junqueira, L. C. U. (2016). Junqueira's basic histology: Text and atlas (Fourteenth edition.). New York: McGraw-Hill Education.</ref>