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Cutaneous metastases from breast cancer.

In this issue of the SMJ, Conner and Cohen 1 provide an excellent review of the rare alopecia neoplastica syndrome of hair loss from scalp metastasis, which is sometimes a diagnostic problem. All 25 patients were women, and 21 had breast cancer. As such scalp lesions may remain flat for some time, alopecia areata, an inflammatory condition with discrete areas of hair loss, may be suspected initially. Eventually plaques develop which may become nodular and erythematous; even then, such lesions may be mistaken for inflammatory dermatitis. Hair loss appears to be due to the destruction of pilosebaceous units by a dense collagenous stroma formed by scalp metastases. Alopecia neoplastica should be considered in the context of skin metastasis from breast cancer, their most common source in this and other cutaneous regions. A random pattern of hair loss in a breast cancer patient, not due to radiation or chemotherapy, should suggest alopecia neoplastica. Another example of localization of breast metastasis to a specific cutaneous field is eyelid involvement, with histiocytoid features. Such metastases are probably hematogenous and rarely the first sign of breast cancer. Scirrhous changes are common in primary breast cancer, and also occur in cutaneous metastases at other sites. Most cutaneous breast cancer metastases probably spread from the primary tumor by lymphatic routes. This is true of the en cuirasse pattern, in which the chest skin metastases are continuous and fibrotic. So-called skip metastases to cutaneous regions adjacent to the primary tumor, such as the skin of the contralateral breast and upper trunk may occur, with intervening, apparently normal skin regions. Continuous spread through lymphatic local vessels may be prevented by obstruction via surgery or radiation. Tumor cells in obstructed blood vessels may cause telangiectatic breast cancer skin lesions. Although the cases reported here, and most cutaneous metastases, are intradermal, movable subcutaneous nodules, initially without dermal involvement, may sometimes be the origin of skin involvement, and can be observed to infiltrate the dermis. Breast cancer itself usually arises from the mammary ducts, which are ectodermal appendages; a few breast cancers resemble the apocrine glands from which mammary parenchyma arises. This may account for its predilection for cutaneous metastases, which it shares with melanoma. Neglected tumors may directly infiltrate the skin (T4b), and chest wall surgical scar recurrences are common. These are manifestations of locally advanced (stage IIIB) breast cancer; more distant cutaneous metastases imply stage IV disease. Yet, in the absence of internal metastases, some such patients may have a surprisingly good prognosis; I and others have observed prolonged survival, and even cure of some. Skin lesions are excellent markers for response to systemic therapy. The management of cutaneous recurrences in breast cancer patients is determined by whether or not they are known to have internal metastases. If not, restaging is indicated to rule them in, but a negative result does not rule out metastases too small ( 10 cells) to be detected by imaging; overt internal metastases will ultimately develop in about two thirds of patients with cutaneous recurrence. For this reason, I initially treat all such patients with a systemic therapy which they have not yet received; in effect, salvage adjuvant therapy. If their skin lesions do not respond to a month or two of treatment, another systemic therapy, if available, should be initiated. Since skin lesions are likely to ulcerate, and may become the source of new distant metastases, the regions in which those responsive to systemic therapy arose should then be irradiated. Durable control is often achieved. If no internal metastases are present, and skin lesions were refractory, or occurred in previously irradiated fields, they should be resected. A similar approach to alopecia neoplastica may be appropriate, though radiation itself causes alopecia. Surgery may be considered for patients with localized lesions and without internal metastases.