Case 2 -

So-called biopsy associated epithelial displacement in the setting of an intracystic papillary carcinoma

History: This 55-year old woman had undergone a prior core needle biopsy that showed an "atypical papillary intraductal proliferation, suspicious for ductal carcinoma in situ." The subsequent excision showed ductal carcinoma in situ arising in association with a papilloma. How would you interpret the cellular focus that was adjacent to a duct that contained ductal carcinoma in situ? Case 2 - Figure 1 Case 2 - Figure 2 Diagnosis: So-called biopsy associated epithelial displacement in the setting of an intracystic papillary carcinoma. Discussion: Rosen and others have called attention to a histologic finding, which may be confused with microinvasion, that they termed "displaced" epithelium associated with needle biopsy procedures. By use of the word "displacement" they are implying a mechanical process, caused by the biopsy needle device pushing (or pulling) clumps of epithelium out of ducts and into surrounding stroma. Displacement may involve vascular spaces as well as stroma. It may develop in both benign and malignant lesions, particularly those with ducts that are distended by architecturally-complex, papillary, or highly cellular proliferations. Although generally focal, we have observed dramatic examples, with numerous foci. Displaced epithelium may be recognized by recognition of several characteristic features. First, displaced epithelium is geographically associated with biopsy site changes including hemorrhage, organizing inflammation, and granulation tissue. This, admittedly, may resemble tumor-associated desmoplasia. However, in most cases low magnification observation reveals that displaced clumps tend to be deposited as foci, often multiple, that course along biopsy tracts. Second, displaced epithelium tends to form isolated spheroids of cells; these are very small and may be inconspicuous at low magnification. There is no tendency to form larger or confluent nests. These spheroids are very sharply demarcated, without "single cells", and often separated from stroma by a thin clear space not unlike a retraction artifact. Finally, displaced cell nests often have a characteristic squamoid appearance. Displaced nests, whether benign or malignant, are presumed to be biologically inert. They have no proven clinical significance. Obviously, the main point is to avoid diagnosing such foci as microscopic invasive neoplasm. References: Youngson B, Cranor M, Rosen P. Epithelial displacement in surgical breast specimens following needling procedures. American Journal of Surgical Pathology 1994; 18(9):896-903.