[92] Metastatic Melanoma Presenting as Isolated Breast Tumor: A Study of 20 Cases

Carlos E Bacchi, Sheila C Wludarski, Abiy B Ambaye, Janez Lamovec, Giovanni Falconieri. Consultoria em Patologia, Botucatu, SP, Brazil; Institute of Oncology, Ljubljana, Slovenia; University of Vermont, Burlington, VT; General Hospital, Udine, Italy

Background: Breast may be invoved by metastasis in widely metastatic melanoma (MM) which is easily recognized microscopically if clinical information is available. However, MM presenting as an isolated mammary tumor may be more challenging to recognize since it may simulate a primary tumor clinically and morphologically.
Design: Cases of MM clinically presenting as breast tumors were retrieved. Breast MM in patients with systemic metastases or melanoma of the mammary skin were excluded. A panel of antibodies against keratins, S100 protein, gp100, and melan A was applied.
Results: 20 cases (17 females; 3 males) fulfilling the search criteria were included in the study. The age range was 27 to 91 years, median 47.5 years. A history of cutaneous melanoma was obtained in 19 cases; 1 patient had a history of choroid melanoma. Tissue material consisted mostly of core needle biopsy or limited excision specimens, although mastectomy was performed in two cases. 6 cases had been submitted as consultation material for “suspected breast cancer” for confirmation and/or for ER/PR and Her2 status assessment. The initial diagnoses proffered included high-grade invasive ductal (5 cases) or papillary carcinoma (2 cases) due to sheets of polygonal cells or pseudopapillary fronds, respectively. Diverging differentiation findings were also noticed, including sheets of monotonous small cells percolating through the breast fat (suggesting large-cell lymphoma), intersecting fascicles of cohesive cells (sarcomatoid carcinoma), cell nests admixed with lymphoid stroma (medullary carcinoma), lipoblast-like cells within a myxoid stroma (liposarcoma or lipophyllodes tumor). Tumor cells were negative for keratins and positive for S100 protein (20/20), gp100 (16/18) and melan A (14/16).
Conclusions: MM involving the breast may simulate a wide spectrum of primary breast malignancies. Although the application of a simple panel of antibodies assist in rendering the correct interpretation, a significant diagnostic bias may be introduced by lesions presenting as isolated tumors, especially when a timely history of primary cutaneous melanoma is not available or is even neglected by the patient. Further challenges are introduced by the extraordinary phenotypic plasticity of MM. Awareness of this pattern variance in the breast may be useful to avoid inappropriate treatment, especially in cases simulating a “triple negative” poorly differentiated carcinoma of the breast.
Category: Breast

Monday, March 19, 2012 1:00 PM

Poster Session II # 52, Monday Afternoon


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