Skin - Hyperplasia



comment:
Epithelial hyperplasia is the most common spontaneous, non-neoplastic lesion of the skin observed in B6C3F1 mice in NTP studies. Hyperplasia of the epithelium of the epidermis and adnexa is also a common response to dermal application of chemicals. In more severe cases, especially when accompanied by inflammation, hyperplasia of follicular epithelium, follicular units, and sebaceous glands often occurs. It is characterized by increased thickness of the nonkeratinized layers of the epidermis due to an increased number (layers) of epithelial cells ( Figure 2


Sebaceous gland hyperplasia is characterized by large sebaceous glands with increased numbers of cells forming numerous lobules around central ducts ( Figure 3


Follicular hyperplasia is characterized by increased numbers of follicular units within the dermis and subcutis ( Figure 5

recommendation:
“Epithelial hyperplasia” is preferred over the term “acanthosis.” Whenever present, epithelial hyperplasia should be diagnosed and assigned a severity grade. When follicular epithelium is also hyperplastic, this should be reflected in the severity grade assigned to epithelial hyperplasia and described in the pathology narrative. If follicular epithelial hyperplasia occurs without epidermal involvement, the term “Skin, Hair follicle, Epithelium – Hyperplasia” should be used. Associated lesions, such as inflammation, should be diagnosed separately. When present as a regenerative response, secondary to an adjacent ulcer, hyperplasia should not be diagnosed but should be described in the narrative.When present, sebaceous hyperplasia or follicular hyperplasia should be diagnosed and assigned a severity grade. Hyperplasia of the sebaceous cells is often accompanied by hypertrophy. In such cases, hypertrophy need not be diagnosed.
references:
Elwell MR, Stedman MA, Kovatch RM. 1990. Skin and subcutis. In: Pathology of the Fischer Rat: Reference and Atlas (Boorman GA, Eustis SL, Elwell MR, Montgomery CA, MacKenzie WF, eds). Academic Press, San Diego, 261-277. Abstract: https://www.ncbi.nlm.nih.gov/nlmcatalog/9002563
Klein-Szanto AJP, Conti CJ. 2002. Skin and oral mucosa. In: Handbook of Toxicologic Pathology, 2nd ed (Haschek WM, Rousseaux CG, Wallig MA, eds). Academic Press, San Diego, 2:85-116. Abstract: http://www.sciencedirect.com/science/book/9780123302151
Peckham JC, Heider K. 1999. Skin and subcutis. In: Pathology of the Mouse: Reference and Atlas (Maronpot RR, Boorman GA, Gaul BW, eds). Cache River Press, Vienna, IL, 555-612. Abstract: http://www.cacheriverpress.com/books/pathmouse.htm
Web page last updated on: January 02, 2014