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Given a neoplasm of uncertain behavior of skin on a patient's face that is suspected to be a basal cell carcinoma (BCC), the typical first step is to perform a shave biopsy to determine the type of basal cell carcinomas so that one can decide the treatment {1}.

The downside of a shave biopsy is that it leaves a small scar.

The main 4 types of BCCs are:

  • superficial: often treatable with imiquimod cream {2,3,4},
  • nodular: sometimes treatable with imiquimod cream {2,3},
  • micronodular: requires surgery (preferably Mohs if on face for cosmetic reason),
  • infiltrative: requires surgery (preferably Mohs if on face for cosmetic reason).

Why isn't imiquimod cream used prior to performing a biopsy used for a suspected facial basal cell carcinoma?

Rationale: if imiquimod cream is successful in treating the BCC, no need to perform a biopsy.


References:

  • {1} Medscape (mirror):

    A skin biopsy is often required to confirm the diagnosis and determine the histologic subtype of basal cell carcinoma (BCC). Most often, a shave biopsy is all that is required. [Mar 2, 2020]

  • {2} Bath-Hextall, Fiona, Mara Ozolins, Sarah J. Armstrong, Graham B. Colver, William Perkins, Paul SJ Miller, and Hywel C. Williams. "Surgical excision versus imiquimod 5% cream for nodular and superficial basal-cell carcinoma (SINS): a multicentre, non-inferiority, randomised controlled trial." The lancet oncology 15, no. 1 (2014): 96-105. https://doi.org/10.1016/S1470-2045(13)70530-8

    Imiquimod was inferior to surgery according to our predefined non-inferiority criterion. Although excisional surgery remains the best treatment for low-risk basal-cell carcinoma, imiquimod cream might still be a useful treatment option for small low-risk superficial or nodular basal-cell carcinoma dependent on factors such as patient preference, size and site of the lesion, and whether the patient has more than one lesion.

    [Note: I believe the statement "Although excisional surgery remains the best treatment for low-risk basal-cell carcinoma" is incorrect, as from what I recall Mohs surgery has been shown to yield superior results compared to excisional surgery.]

  • {3} https://dermnetnz.org/topics/imiquimod/

    Imiquimod is mainly used to treat: [...] Basal cell carcinoma (BCC), especially superficial BCC and sometimes low-risk nodular BCC

  • {4} Raasch, Beverly. "Management of superficial basal cell carcinoma: focus on imiquimod." Clinical, cosmetic and investigational dermatology: CCID 2 (2009): 65. https://dx.doi.org/10.2147%2Fccid.s3507 ; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3047930/

    To date one long-term study indicates a treatment success rate [of Imiquimod for superficial BCCs] of 78%–81% and that initial response is a predictor of long-term outcome. Recurrences tend to occur within the first year after treatment. Future research will com


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