Synchronous Sentinel Lymph Node Metastasis of Lobular and Ductal Carcinoma Deepak Mohan, MD; Brian R. Mullin, MD; David J. Dabbs, MD
A
45-year-old woman presented with a palpable 2.0-cm mass in the right breast. Segmental mastectomy with sentinel lymph node biopsy was performed. Grossly the tumor was firm, stellate, and ivory-tan. Two distinct invasive populations were seen histologically: small irregular tubules infiltrating stroma in well-defined nests (well-differentiated infiltrating ductal carcinoma [IDC]) (Figure 1, A) and uniform, small, loosely cohesive cells infiltrating stroma in a single-file pattern (infiltrating lobular carcinoma [ILC]) (Figure 1, B). Surprisingly, the sentinel lymph node when stained for cytokeratin AE1/3 also showed 2 distinct metastatic populations, ductal (Figure 2, A) and lobular (Figure 2, B). Ecadherin immunoreactivity confirmed the ductal nature of the metastatic IDC cells (Figure 3, A); metastatic ILC cells did not stain (Figure 3, B). Small size, uniformity, lack of cohesiveness, and singlefile pattern are the most important distinguishing features of ILC.1 The morphologic distinction between IDC and ILC is, to a large extent, subjective, as borne out by the fact that the incidence of ILC ranges from 0.7% to 20% in published series.1 The immunohistochemical staining pattern for E-cadherin has helped differentiate IDC from ILC.2,3 Ductal epithelium expresses this surface adhesion protein on its surface membrane, whereas lobular epithelium does not.2,3 The differential diagnosis of ILC includes pure poorly differentiated IDC, mixed infiltrating ductal and lobular carcinoma, carcinoid tumor, and malignant lymphoma. Immunohistochemical staining is especially helpful in distinguishing ILC in axillary sentinel lymph nodes.3 We gratefully acknowledge the personnel of the Histology Laboratory at Magee-Womens Hospital, Pittsburgh, Pa. References 1. Rosai J. Ackerman’s Surgical Pathology. 8th ed. St Louis, Mo: Mosby-Year Book Inc; 1996:1433–1437. 2. Dabbs DJ. Diagnostic Immunohistochemistry. 1st ed. Philadelphia, Pa: Churchill Livingstone Co; 2002. 3. Oka H, Shiozaki H, Kobayashi K, et al. Expression of E-cadherin cell adhesion molecules in human breast cancer tissues and its relationship to metastasis. Cancer Res. 1993;53:1696–701.
Accepted for publication October 29, 2003. From the Department of Pathology, Division of Anatomic Pathology, Magee-Womens Hospital, University of Pittsburgh Medical Center, Pittsburgh, Pa. The authors have no relevant financial interest in the products or companies described in this article. Reprints: Deepak Mohan, MD, Department of Pathology, Division of Anatomic Pathology, University of Pittsburgh Medical Center, 260 Lothrop St, A614, Pittsburgh, PA 15260 (e-mail:
[email protected]. edu). Arch Pathol Lab Med—Vol 128, March 2004
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