5.1 Pathology of basal cell carcinoma
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)[edit source]
Recurrence of basal cell carcinomas[edit source]
Basal cell carcinomas may be locally destructive, but very rarely metastasise. 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, sclerosing (morphoeic) or superficial multifocal subtype. The risk of recurrence is greater if combinations of such features are present.
- tumours on the nose or nasolabial fold
- tumours recurring after previous radiotherapy
- tumours associated with perineural spread, particularly on the head and neck
- naevoid BCC syndrome (Gorlin's syndrome), which is rare
- immunosuppression (see: Organ transplantation and other conditions associated with prolonged immunosuppression).
Histological diagnosis of basal cell carcinomas[edit source]
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.
The clinical location, the architectural pattern and excision margins should be considered when determining the risk of recurrence.
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