Contributed by Stacey Barron, MD, Amal Kanbour-Shakir, MD and David Dabbs, MD
The patient is a 69 year old female with a history of bilateral breast cancer. In late 1995, she underwent a segmental mastectomy of the left breast that demonstrated invasive ductal carcinoma. Immunohistochemical staining was interpreted as borderline expression of estrogen receptor and negative expression of progesterone receptor. A few months later, in early 1996, she underwent a right total mastectomy with axillary dissection for invasive ductal carcinoma with a lobular component and signet ring features metastatic to thirteen out of thirteen axillary lymph nodes. The tumor in the left axillary lymph nodes was morphologically similar to the tumor of the left breast. Given that the mass of the right breast shared only part of the features of the left breast carcinoma, a second primary could not be ruled out. She was also treated with Tamoxifen, chemotherapy and radiation therapy to the right chest wall and left breast.
Sixteen years later, in early 2012, she began to have bone pain. Radiologic imaging demonstrated several sclerotic lesions within the pelvis. A CT-guided biopsy of the left iliac bone demonstrated metastatic breast carcinoma (Figure 1 and Figure 2). Following this diagnosis, she was initiated on another chemotherapy regimen as well as radiation therapy.
In the summer of 2013, she presented with complaints of intermittent leg swelling around her psoriasis and a new palpable lymph node in her right groin. On physical exam, left and right lower extremity psoriasis was noted to be present as well as psoriatic spots on the arms and buttocks. No additional skin lesions except for her psoriatic plaques were noted on her exam. In addition, her dermatologist did perform a recent head to toe exam which did not reveal any suspicious lesions. The enlarged lymph node measured up to 1.5 cm.
A CT of the chest, abdomen and pelvis demonstrated the known diffuse sclerotic bony metastases of the pelvis and lumbar spine without interval change. No visceral metastatic disease was identified within the abdomen. The newly enlarged right inguinal node was confirmed on CT and presumed to be metastatic disease. She subsequently underwent biopsy of the right inguinal mass.
On low power, histologic sections demonstrate a soft tissue core biopsy with irregular nests of basophilic tumor cells (Figure 3). High power view demonstrates sheets and clusters of small, round to oval cells of uniform size. The nucleus is vesicular and nucleoli are present. The cells have scant cytoplasm with indistinct cytoplasmic borders. Numerous scattered apoptotic bodies and mitotic figures are seen (Figure 4). The morphology of the current tumor in the right groin is DIFFERENT from the metastatic breast tumor.
The tumor cells demonstrate diffuse positive expression for synaptophysin and patchy positivity for chromogranin (Figure 5). CK20 and CAM 5.2 demonstrate paranuclear dot-like positive expression (Figure 6). The tumor cells are negative for CK7, TTF-1, ER, and mammaglobin (Figure 7), and also negative for GCDFP-15, PAX8, PR and Her-2/neu. The tumor proliferation index by ki-67 is very high (90%) (Figure 8). Additionally, the tumor cells demonstrate patchy nuclear positive expression for Merkel cell polyomavirus (Figure 9).