Cutaneous metastases from solid tumors in general occur at a rate of about 1% per primary tumor.1 In breast cancer, cutaneous metastases occur at a rate of about 2.5% per primary tumor. Because of the high incidence of breast cancers relative to other internal malignancies, breast cancer accounts for almost 33% of all cutaneous metastases.2 Infiltrating ductal carcinoma accounts for almost 70% of cutaneous metastases from breast cancers, whereas lobular carcinoma accounts for about 15%.
Cutaneous metastases may be the first presenting sign of primary malignancy. In one retrospective study, 6% of breast carcinomas (N=992) initially presented with only skin manifestations.3 Clinical appearance can vary, but cutaneous metastases from breast adenocarcinomas often present as isolated dermal nodules with superficial discoloration or changes in texture. The most common location of cutaneous metastases is on the chest ipsilateral to the primary breast malignancy.4 We pre-sent a case of metastatic adenocarcinoma of the breast presenting with diffuse cutaneous nodules with no surface changes.
Case Report
A 64-year-old woman who was otherwise in good health presented to her primary care physician for evaluation of recent-onset fatigue. Laboratory testing revealed that she was mildly anemic with mild thrombocytopenia and lymphocytosis. She was referred to a hematologist, who ordered flow cytometry and cytogenetic testing. Blood abnormalities were not considered severe enough to warrant a bone marrow biopsy, and she was monitored clinically for the next 2 years.
Two years after the initial presentation, the primary care physician performed a breast examination that was unremarkable, but enlarged axillary lymph nodes up to 15 mm were discovered in the right breast during routine breast ultrasonography. Additionally, she noted that she had experienced unintentional weight loss of 10 lb over the past year. The hematologist suspected a low-grade lymphoma and performed a bone marrow biopsy. The immunohistochemistry of the bone marrow specimen was consistent with an estrogen receptor–positive, progesterone receptor–negative, human epidermal growth factor receptor 2–negative invasive lobular breast carcinoma, which was then confirmed in the right breast on magnetic resonance imaging. The patient denied any history of prior radiation treatment, but she disclosed a family history of breast cancer in her cousin.
Several weeks after the bone marrow biopsy, an oncologist found that the patient also had an abdominal mass and bone metastases of the primary breast cancer. Colonoscopy confirmed metastases to the colon that subsequently led to obstruction and ultimately required a right hemicolectomy. The patient’s oncologist started her on anastrozole, an aromatase inhibitor (AI), for treatment of the metastatic breast cancer and zoledronic acid, a bisphosphonate, along with calcium and vitamin D for the bone involvement.
Shortly after, during a routine annual skin examination, the patient’s dermatologist (H.T.N.) discovered 3 soft, fixed, subcutaneous-appearing nodules—one on the right chest that was 15 mm in diameter, one on the left mid back that was 7 mm, and one on the left upper anterior thigh that was 10 mm. They were discrete with well-defined borders but had only minimal elevation, making them difficult to detect clinically, especially without palpation. The nodules were not visibly apparent because they were flesh-colored with no surface discoloration or texture changes. The patient remembered that the lesions had appeared gradually several months prior, predating the breast cancer diagnosis, and were not associated with pain, itching, or burning, so she was not alarmed by their appearance and never sought medical attention. The dermatologist (H.T.N.) recommended a biopsy at the time of the skin examination, but the patient declined.
One year after the appearance of the first skin lesions, 14 more nodules (Figure 1) progressively erupted on the ipsilateral and contralateral chest (Figure 2A), axillae, arms, shoulders, back (Figure 2B), and thighs (Figure 2C). At this point, the dermatologists performed a punch biopsy on a lesion on the back to confirm the suspicion of cutaneous metastasis of the primary breast cancer. The biopsy showed interstitial dermal proliferation of atypical cells between collagen bundles and stained strongly positive for cytokeratin 7, an epithelial protein common in breast adenocarcinoma (Figure 3). Further immunohistochemical staining returned metastatic estrogen receptor–positive, progesterone receptor–negative, human epidermal growth factor receptor 2–negative invasive lobular breast carcinoma. Therefore, the markers for the cutaneous metastases were consistent with the markers for the original breast cancer.
Figure 1. Map of all cutaneous metastases (indicated in yellow) present 1 year after the appearance of the initial metastases. Lesions were present on the ipsilateral chest, contralateral chest, axillae, arms, shoulders, back, and thighs.
Figure 2. Cutaneous metastasis of a primary adenocarcinoma of the breast. Lesions sites included the right chest (A), back/shoulder (B), and left thigh (C)(arrows).
Figure 3. A biopsy from a lesion on the back showed interstitial dermal proliferation of atypical cells between collagen bundles (A)(H&E, original magnification ×400) and strong positive staining with cytokeratin 7 (B)(original magnification ×100).
After 1 year of treatment with anastrozole, the patient’s internal metastases had not changed considerably, but the cutaneous metastases continued to grow—the lesion on the left thigh doubled from 10 to 20 mm in diameter, and new nodules developed on the chest, back, arms, and legs. One year and a half after the initial lesions were documented, several nodules had disappeared and several new ones appeared. The remaining nodules remained relatively constant in size.
After stopping anastrozole, the patient was enrolled in a research trial using bortezomib, a chemotherapeutic agent typically used for multiple myeloma, as well as fulvestrant, an estrogen receptor antagonist; however, because of continued progression of the metastatic cancer, the patient was removed from the trial and switched to the established regimen of everolimus, a chemotherapeutic agent, and exemestane, another AI. Everolimus eventually was stopped, but the patient continued on exemestane as monotherapy. In addition to development of pleural disease, the cutaneous metastases continued to progress. The patient did not receive any local treatment for her cutaneous metastases.