5.1 Pathology of basal cell carcinoma

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Clinical practice guidelines for keratinocyte cancer > 5.1 Pathology of basal cell carcinoma


Background

Basal cell carcinomas (BCCs) are a group of tumours comprising masses of basaloid cells with hyperchromatic nuclei and scanty cytoplasm, resembling cells of the basal layer of the epidermis and of follicular epithelium. The tumour has a blue cell appearance.

Overview of evidence (non-systematic literature review)

Recurrence of basal cell carcinomas

Basal cell carcinomas may be locally destructive, but very rarely metastasise.[1] Local recurrence is not uncommon. There is an increased risk of local recurrence for large, deep or ulcerated tumours, especially if incompletely or narrowly excised, and for tumours of micronodular, infiltrating, sclerosingscar-like (morphoeic) (morphoeic) or superficial multifocal subtype.[2][3][4] The risk of recurrence is greater if combinations of such features are present.

Other presentations and features associated with a higher risk of recurrence include (Table 1):[5][6]

Table 1. Tumour-specific factors associated with recurrence of basal cell carcinoma Table 1 KC guideline Tumour specific factors BCC .png

Histological diagnosis of basal cell carcinomas

Histological diagnosis of BCCs is usually straightforward. Most tumours are of nodular or nodulocystic subtype. Frequently, the tumour shows a mixed pattern.

Superficial BCC is a common subtype and frequently occurs on the trunk. It is characterised by small basaloid groupings attached to the deep aspect of the epidermis and is sometimes associated with a deeper nodular component.

Peripheral nuclear palisading is a characteristic feature of most BCCs.

Differential diagnoses that should be considered include cutaneous squamous cell carcinoma (with basaloid cell features), Merkel cell carcinoma (an aggressive tumour; see Pathology of rare tumours) and various skin appendage tumours (commonly benign), particularly those of follicular origin.

Special staining by immunochemistry can be helpful. Basal cell carcinoma is typically positive for cytokeratin and Ber-ep4, and negative for epithelial membrane antigen (EMA). Merkel cell carcinoma is diffusely positive for cytokeratin 20 (CK20). Cytokeratin 20 is also useful in follicular neoplasms, which may contain a few CK20-positive Merkel cells.


Key point(s)

The clinical location, the architectural pattern and excision margins should be considered when determining the risk of recurrence.


References

  1. Lo JS, Snow SN, Reizner GT, Mohs FE, Larson PO, Hruza GJ. Metastatic basal cell carcinoma: report of twelve cases with a review of the literature. J Am Acad Dermatol 1991 May;24(5 Pt 1):715-9 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/1869642.
  2. Dellon AL, DeSilva S, Connolly M, Ross A. Prediction of recurrence in incompletely excised basal cell carcinoma. Plast Reconstr Surg 1985 Jun;75(6):860-71 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/4001206.
  3. Salasche SJ, Amonette RA. Morpheaform basal-cell epitheliomas. A study of subclinical extensions in a series of 51 cases. J Dermatol Surg Oncol 1981 May;7(5):387-94 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/7240543.
  4. Sloane JP. The value of typing basal cell carcinomas in predicting recurrence after surgical excision. Br J Dermatol 1977 Feb;96(2):127-32 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/843446.
  5. Mierzwa ML. Radiotherapy for Skin Cancers of the Face, Head, and Neck. Facial Plast Surg Clin North Am 2019 Feb;27(1):131-138 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/30420066.
  6. Armstrong LTD, Magnusson MR, Guppy MPB. Risk factors for recurrence of facial basal cell carcinoma after surgical excision: A follow-up analysis. J Plast Reconstr Aesthet Surg 2017 Dec;70(12):1738-1745 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/28579037.

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