CUTANEOUS METASTASES
Metastasis
to the skin is an uncommon presentation of internal malignancy. Cutaneous
metastases are far more likely to be seen in a patient with a diagnosis of
previously metastatic disease. The frequency of cutaneous metastasis is
dependent on the primary tumor. Almost all types of internal malignancy have
been reported to metastasize to the skin; however, a few types of cancers
account for the bulk of cutaneous metastases. The distribution of the
metastases is also dependent on the original tumor. The most common form of
skin metastasis is from an underlying, previously metastatic melanoma.
Clinical Findings: Most cutaneous metastases mani- fest as slowly
enlarging, dermal nodules. They are almost always firm and have been shown to
vary in coloration. Some nodules eventually develop necrosis, ulcerate, and
spontaneously bleed. Skin metastasis can occur as a direct extension from an
underlying malignancy or as a remote focus of tumor deposition. Although skin metastasis
often arises in the vicinity of the underlying primary malignancy, the location
of tumor metastases is not a reliable means of predicting the primary source.
The scalp is a common site, probably because of its rich vascular flow.
Sister Mary Joseph nodule is a name given to a periumbilical skin metastasis
from an underlying abdominal malignancy. This is a rare presentation that was
first described by an astute nun at St. Mary’s Hospital at the Mayo Clinic.
This has been described to occur most commonly with ovarian carcinoma, gastric
carcinoma, and colonic carcinoma.
Melanoma metastases are usually
pigmented and tend to occur in groups. Cutaneous metastasis from melanoma can
manifest with the rapid onset of multiple black papules and macules that continue
to erupt. As the tumors progress, patients can develop a generalized melanosis.
This is a universally fatal sign that occurs late in the course of disease. It
is believed to be caused by the systemic production of melanin with deposition
in the skin.
Breast carcinoma is another form of
malignancy that frequently metastasizes to the skin. Breast carcinoma tends to
affect the skin within the local region of the breast by direct extension.
Pathogenesis: The exact reason why some tumors metastasize to
the skin is unknown. This is a complex biological process that is dependent on
many variables. Metastases are likely to be dependent on size, ability to
invade surrounding tissues (including blood and lymphatic vessels), and ability
to grow at distant sites far removed from the original tumor. This is an
intricate process that depends on the production of multiple growth factors and
evasion of the patient’s immune system.
Histology: The diagnosis of cutaneous metastasis is almost
always made by the pathologist after histological review. Each tumor is unique,
and the histological picture depends on the primary tumor.
Treatment: Solitary cutaneous metastases can be surgically
excised. The risk of recurrence is high, and adjunctive chemotherapy and
radiotherapy should be considered. Palliative surgical excision can be
under-taken for any cutaneous metastases that are painful, ulcerated, or
inhibiting the patient’s ability to function. The prognosis for patients with
cutaneous metastasis is poor. The overall survival rate for multiple cutaneous
metastases has been reported to be 3 to 6 months. The length of survival is
increasing now because of improved treatments.
