Contributed by Vandana Baloda, MD, Sonal Choudhary, MD and Rohit Bhargava, MD
A female in her early 70s was found to have a left breast lesion (detected on imaging studies) at an outside institution. It measured 0.7 cm and was located in the upper outer quadrant at 1 O'clock position. Dermatopathology services received the slides as a consult with limited history. The case was subsequently forwarded to division of breast pathology for further characterization.
Needle core biopsies showed a large dermal based neoplasm arranged in well-formed nests of basaloid cells, arranged in a jigsaw puzzle pattern (Fig. 1). The tumor showed low-grade cytologic features and low mitotic activity. No in-situ carcinoma was identified (Fig. 2). Based on the morphology, two possibilities were considered: adenoid cystic carcinoma and cylindroma. However, a p63 stain was negative. The initial antibody panel showed the tumor cells to be GATA3 negative, GCDFP-15 negative, mammaglobin negative, ER scattered weak positivity (Fig. 3), PR negative, E-cadherin & p120: membranous expression, CK20 negative, CK5 negative, CD1a negative, S100 negative, c-kit negative and chromogranin positive (Fig. 4). Low-grade neuroendocrine tumors of mammary origin are almost always strongly and diffusely ER positive, and since the current tumor showed only weak ER reactivity, additional markers to include breast (luminal and basal) markers and other site specific markers were performed. Tumor cells had the following immunoprofile: AE1/AE3-positive, basal markers (SOX10, CK14) - negative, AR-negative, site specific markers (CK7-negative, TTF1-negative, PAX 8-negative, CDX2-positive, SATB2- positive) (Figs. 5, 6 and 7).