3.3.10 Cutaneous Metastases

Skin metastases; skin secondaries.

Prevalence is around 2%, incidence varying from 8 - 10%. In up to 10%, skin manifestation is the first visceral tumor sign or leads to source of origin via histological examination. Most common sources: breast, colon and lung carcinomas as well as leukemias followed by ovarian, head & neck and throat, renal cell - and gastrointestinal carcinoma.

There is no clear pathomechanism behind why metastases localise to the skin except by direct penetration. Some homing factors can play a role in leukemia dissemination. Sometimes skin metastases are found in a post-zosteric area.

Solitary or multiple, firm blue-red to yellow papules and nodules in various levels of the skin with rapid growth and a short history. Most CMs exhibited a single pattern, with pink and red coloration, irregular or dotted vessels, and occasional dots, globules, lines, streaks, lacunae, or milky-red structures. Appearing as single lesion or aggregated, zosteriform or disseminated. Sometimes erysipela-like pattern or lymphangiosis-like (cancer en cuirasse) in mammary carcinoma.

Allocation of the localisation of a skin metastasis with regard to the original tumour is not possible. Exceptions are penetrating tumors to skin fom bone, muscle, fascia or joint. Mammary carcinomas are often thoracical, prostate suprapubic. Sister Mary Joseph’s nodules located at the umbilicum derive from the ovarian and gastro-intestinal origin. Oesophageal, gastric and colonic cancers, biliary tract, pulmonary and renal carcinomas prefer hairy scalp, neck and face.

Estimated frequencies of cutaneous metastases:

Frequency of renal and urogenital cancer CMs

• Renal cancer: 4-8 %

• Bladder cancer: < 4 %

• Prostate cancer: 1 %

• Uterine cancer: very rare

• Cervical cancer: < 2 %

• Ovarian cancer: 3.5 %

Frequency of gastro-intestinal cancer CMs

• Colo-rectal cancer 11 % in male / in female 1.3 %

• Gastric cancer < 1.5 %

• Pancreatic cancer 2 %

• Hepato-cellular cancer <1 %

Frequency of breast cancer CMs

• about 30 % of all breast cancer metastases involve the skin

Frequency of lung and pleural cancers CMs

• Lung cancer: 1.8 - 11 % / small cell type lowest incidence

• Pleural cancer: very rare

No clear classifcation of cutaneous metastases of visceral tumours but grouping them into nodular, inflammatory, fibrotic and sclerodermic-like types is widely accepted.

First action is a biopsy or complete resection for histopathological evaluation. Often immunohistochemistry or modern molecular cell differentiation is indicated. Thereafter, tumor screening with different methods (i.e. serum, different imaging techniques) follow.

Depends on origin of cell and tumor. Mostly needs immunhistochemistry and molecular typing.

Depending on the type of primary tumor, stage, pretreatment and available resources of modern surgical, radiologic or chemotherapeutic / biologic / targeted cancer treatment. Some metastases melt, become necrotic or bleed or become superinfected.

Whenever an unknown lesion in the skin appears slowly or rapidly and when it cannot be classified to the spectrum of benign or malignant tumors of the skin or certain dermatoses.

There is no prevention. Biopsy or excision for diagnosis is a first step to lead to decision algorithms of therapy according to the individual tumor.