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infiltrative basal cell carcinoma

Wednesday 22 May 2013

Infiltrating type

This type, consisting of 10% of all BCC, includes non-sclerosing and sclerosing histological variants with an infiltrating rather than expansible growth pattern, where long, thin strands of tumour cells penetrate deeply among the collagen fascicles.

The superficial layers of the tumour often have a solid growth pattern and the infiltrative type is present in the lower or peripheral layers of the tumour.

If excision is not complete, this tumour can be included in the nodular type and the
infiltrative type is detected only during re-excision.

The sclerosing (morpheic, fibrosing, cicatricial or desmoplastic) variant of infiltrative BCC is characteristic of an increased number of fibroblasts and the presence of fibrotic desmoplastic stroma, which gives the tumour a characteristic clinical picture of a morphea or keloid scar.

Non‑sclerosing variant

This non‑sclerosing variant has an infiltrative rather than an expansile pattern of growth. It accounts for approximately 5% of all tumors, although this figure is higher in some patient groups.

The histological features are distinctive, with elongated strands of basaloid cells, cells thick, infiltrating between collagen bundles. Sometimes, even narrower strands are present, with spiking projections. There may be a slight increase in fibroblasts, but there is no significant fibrosis. Often there is a solid pattern superficially with the infiltrating nests at the periphery or base of the lesion. Sometimes a focal infiltrative pattern is seen in the re‑excision specimen of a biopsy proven solid (nodular) basal cell carcinoma.

These changes are limited to the region of the biopsy scar and appear to represent a scar induced phenomenon without any sinister connotations.

Like the sclerosing variant, it has a clinically indistinct border, but it differs from that variant in its opaque, yellow‑white color. Metallothionein, a presumptive marker of aggressive clinical behavior, is increased in the infiltrative variant.

Sclerosing type

The sclerosing category includes lesions which have also been referred to as fibrosing, scirrhous, desmoplastic and morpheic.

The uncommon ’field fire’ type with central fibrosis resulting from regression should not be included in this category. Up to 5% of all basal cell carcinomas are of the sclerosing type.

The tumor presents as an indurated, pale plaque with a slightly shiny surface and clinically indistinct margins. There are narrow elongated strands and small islands of tumor cells embedded in a dense fibrous stroma.

If the stroma has dense, eosinophilic areas resembling a keloid, then the term ’morpheic’ has traditionally been used, although at other times this term has been used interchangeably with ’sclerosing’.

The term ’keloidal’ has been applied to basal cell carcinomas with thick sclerotic keloidal collagen bundles in the stroma.

A selectively enhanced procollagen gene expression has been found in the sclerosing variant. Also, large defects have been found in the basal lamina that surrounds the tumor nests. Smooth muscle (x‑actin and myosin) are often present in the stroma.