Diagnosis: Cutaneous metastasis of primary breast cancer
Based on our patient’s history, we gave a presumptive diagnosis of cutaneous breast cancer metastasis. A punch biopsy was performed. The pathology report showed nests of neoplastic cells within the dermis, which was consistent with this diagnosis. Immunohistochemical stains and fluorescence in-situ hybridization confirmed triple-negative breast markers for estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2.
An uncommon phenomenonseen mostly with breast cancer
Cutaneous metastatic carcinoma is relatively uncommon; one meta-analysis reported the overall incidence to be 5.3%.1 While it is unusual, any internal malignancy can metastasize to the skin. In women, the most common malignancy to do so is breast cancer. One study found breast cancer to be associated with 26.5% of cutaneous metastatic cases.2 These metastases often occur well after the patient has been treated for the primary malignancy.
Identifying features. Most cutaneous metastases occur near the site of the primary tumor, initially in the form of a firm, mobile, nonpainful nodule.3 This nodule is typically skin-colored or red, but in the case of cutaneous metastases of melanomas, it can appear blue or black. In the case of breast cancer, the lesions most often arise on the chest and abdomen.4 Occasionally, metastases can ulcerate through the skin.
Some forms of cutaneous metastasis, such as carcinoma erysipeloides, can appear in specific patterns. Carcinoma erysipeloides has a similar appearance to cellulitis; it manifests as a sharply demarcated, red, inflammatory patch in the skin adjacent to the primary tumor.
Consider the clinical picture
Cutaneous metastatic lesions have a wide range of differential diagnoses due to their varied appearances. It is important to view the overall clinical picture when distinguishing such lesions. Although cutaneous metastasis is uncommon, it should always be considered when asymptomatic skin lesions resist treatment—even in someone without a known history of malignancy.
Perform a biopsy. The diagnosis can be confirmed with a skin biopsy. A punch biopsy is preferable, as visualization of the dermis is crucial, and histology often reveals nests of pleomorphic cells. Further cellular cytology can elicit the primary malignancy of origin.
Making our diagnosis
We ruled out several possibilities before arriving at our diagnosis. An infectious etiology (eg, cutaneous candidiasis) was considered, as was a cutaneous change due to radiation therapy. We also considered shingles, the early stages of which would have been similar in appearance to our patient’s lesions, and urticaria, which can manifest as erythematous papules and wheals across various parts of the body. A lack of specific symptoms (eg, pruritis, pain, fever) made these alternative diagnoses less likely. The fact that our patient’s lesions persisted for more than a year without any response to treatment—and that they continued to grow—alerted us of a more sinister etiology.
Continue to: Treating the tumor is often not possible