protuberans is a slowly grow-ing malignant tumour of fibroblasts, arising
usually on the upper trunk. At first it seems like a dermato-fibroma or keloid
but, as it slowly expands, it turns into a plaque of red or bluish nodules with
an irregular protuberant surface. It seldom metastasizes. It should be removed
with extra wide margins, and even then will sometimes recur.
3% of patients with internal cancers have cutaneous metastases. They usually
arise late and indicate a grave prognosis, but occasionally a solitary
cutaneous metastasis is the first sign of the occurrence of a tumour.
most common cutaneous metastases come from breast cancer. The skin of the
breast is also most often involved by the direct extension of a tumour. This
may show up as a sharply demarcated and firm area of erythema (carcinoma
erysipeloides), firm telangiectatic plaques and papules (carcinoma
telan-giectoides) or as skin like orange peel (peau d‚Äôorange)
caused by blocked and dilatated lymphatics. Carcinoma of the breast may also
send metastases to the scalp causing patches of alopecia (Fig. 18.61), or to
other areas as firm and discrete dermal nodules.
common primaries metastasizing to the skin are tumours of the lung,
gastrointestinal tract, uterus, prostate and kidney. The most frequent sites
for sec-ondary deposits are the umbilicus and the scalp.