Which criteria are used to choose whether to perform a shave biopsy or a punch biopsy to diagnose suspected facial basal cell carcinomas?

Question

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}. Punch biopsies are also sometimes used instead of shave biopsies {2,3}.

Which criteria are used to choose whether to perform a shave biopsy or a punch biopsy to diagnose suspected facial basal cell carcinomas? (i.e., confirming whether it is a BCC and if so, determining which type of BCC it is).

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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} https://www.apma.org/files/Derm-%20case%20reports%20APMA%202018.pdf (mirror)

• {3} Fifty-five Basal Cell Carcinomas Treated With Topical Imiquimod: Outcome at 5-Year Follow-up. David Vidal, MD, PhD; Xavier Matías-Guiu, MD, PhD; Agustín Alomar, MD, PhD. Arch Dermatol. 2007;143(2):264-276. https://doi.org/doi:10.1001/archderm.143.2.266

  A 4-mm punch biopsy specimen was taken during the first 3 weeks of therapy to study the mechanism of action of imiquimod in BCC,2 and a final biopsy specimen was obtained 6 weeks after treatment to assess clearance of BCC.

Answer 1

https://emedicine.medscape.com/article/276624-workup#c8 (mirror) explains that using a shave biopsy is the typical biopsy to use but a punch biopsy is preferable in some situations:

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. Nevertheless, in the case of a pigmented lesion where there may be difficulty distinguishing between pigmented BCC and melanoma, an excisional or punch biopsy may be indicated; this is to ensure that the depth of the lesion can be determined if it proves to be a malignant melanoma.

In most cases, a superficial biopsy specimen that contains dermis is all that is required to confirm the diagnosis of BCC, although it is possible to miss the tumor. For example, an ulcerated BCC may reepithelialize with normal epidermis while tumor is still present at a deeper level. Part or all of the BCC may be sampled, but avoid going beyond the clinical margins if the biopsy is only for diagnostic purposes.

Punch biopsy is an easy method to obtain a thick specimen, but is rarely required. The most suspicious area of a lesion may be sampled, or multiple biopsy samples may be taken if the tumor is large or has a varied appearance in different areas. Avoid punch biopsy if curettage is planned for final treatment.