Answer
Answer
Recent reports have shown that papillomas involved by DCIS show loss of heterozygosity (LOH) at several loci on chromosomes 16p and 16q, indicating these are clonal neoplasms. [6, 7] Although LOH at several of these loci have been identified in both IDP and DCIS involving a papilloma, LOH at 16q23 appears to be specific for the latter. [7] This specific LOH seen in DCIS involving a papilloma may reflect a characteristic abnormality in the lesion. However, further study is needed to confirm this.
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Media Gallery
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DCIS (blue arrow) is seen involving a small focus of this IDP (classic IDP present at black arrow). 40x.
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Same tumor as above. 200x. This focus shows all the features of a common, benign IDP, including a single layer of luminal epithelium and a myoepithelial layer (arrow).
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Same tumor as above, at blue arrow. 200x. Low grade DCIS involves the surface of the IDP at this focus, primarily showing a cribriform pattern.
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Same tumor as above, at blue arrow. 400x. This focus shows classic cribriform, low grade DCIS.
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Same tumor as above. 200x. This separate, small focus of DCIS was also present on the IDP.
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Same tumor as above. 400x. The focus of DCIS is low grade with a classic cribriform architecture.
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DCIS (blue arrow) involving an IDP (classic IDP present at black arrow). 40x.
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Same tumor as above, at black arrow. 200x. This focus shows classic features of a benign IDP, with a single layer of luminal epithelium and a myoepithelial layer.
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Same tumor as above, at blue arrow. 200x. The DCIS is characterized by a monotonous proliferation of low grade cells in a cribriform pattern.
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DCIS in an IDP. 100x. This IDP is smaller than the previous examples, and the DCIS component accounts for a larger fraction of the lesion.
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Same tumor as above. 200x. The DCIS is low grade with a predominantly cribriform architecture.
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DCIS involving an IDP. 20x. This field shows areas of common DCIS with comedo necrosis. An IDP is seen in the lower portion of the field.
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Same tumor as above. 200x. DCIS is present on the surface of the IDP.
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Same tumor as above. 400x. A layer of myoepithelium (arrow) is seen underlying a layer of surface epithelium, confirming the suspicion this lesion is composed partly of an IDP.
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Same tumor as above. 400x. This focus shows DCIS, with high grade nuclei and clear cytoplasm, involving the surface of the IDP.
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Same tumor as above. 400x. A focus of DCIS separate from the IDP. This focus has identical histology to the DCIS involving the IDP.
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IDP with prominent apocrine metaplasia. 100x.
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Same IDP as above. 200x. The IDP is involved by extensive, well-developed apocrine metaplasia (volumous pink, granular cytoplasm, enlarged nuclei, and prominent nucleoli). Although the cellular proliferation involving the IDP is monomorphic, the prominent apocrine metaplasia and low grade cytology are strong indicators the proliferation is benign.
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Same IDP as above. 200x. A transition from normal (i.e. not involved by apocrine metaplasia) surface epithelium to epithelium that has undergone apocrine metaplasia is present.
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IDP sampled by core needle biopsy. 40x.
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Same IDP as above. 200x. This IDP is involved by a small proliferation of epithelial cells, seen on the right side of the figure
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Same IDP as above. 400x. The cells comprising the epithelial proliferation are monomorphic, have a moderate amount of pink cytoplasm, and form somewhat uniform spaces. These features are concerning for DCIS.
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Same IDP as above. 200x. This focus shows an area of well-developed apocrine metaplasia (bottom left), and an adjacent focus of hyperplasia. The hyperplasia has undergone apocrine metaplasia, as made evident by comparison with the adjacent area of well-developed apocrine metaplasia. This focus of hyperplasia has very similar histologic features to the previous described proliferation in this IDP concerning for DCIS. As such, the cellular proliferations in this IDP were interpreted as benign.
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IDP with prominent apocrine metaplasia. 100x.
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Same IDP as above. 400x. This focus shows a monomorphic proliferation with abundant pink cytoplasm and low grade nuclei. The findings are concerning for DCIS
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Same IDP as above. 200x. An area of well-developed, definite apocrine metaplasia (bottom of figure) is adjacent to an area with features very similar to the cellular proliferation in the IDP that was concerning for DCIS. Given the close proximity of this proliferation to definite, benign apocrine metaplasia, it is most likely the monomorphism of the proliferation is a result of early apocrine metaplasia.
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Same IDP as above. 400x. Definite well-developed apocrine metaplasia (blue arrow) shows transition from moderately-developed apocrine metaplasia (black arrow). Given this moderately-developed apocrine metaplasia is cytologically indistinguishable from the concerning proliferations in the IDP, we interpreted the concerning proliferations as benign.
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IDP sampled by core needle biopsy. 40x.
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Same IDP as above. 200x. A prominent epithelial proliferation involves the IDP.
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IDP. 400x. The proliferation is composed of monomorphic cells with abundant pink cytoplasm, that form disturbingly round spaces. These features are concerning, but not sufficient for the diagnosis of DCIS.
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Same IDP as above. 200x. In contast to the above previous figure, this cellular proliferation has typical features of UDH.
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Same IDP as above. 200x. A definite focus of UDH without apocrine metaplasia (black arrow) is seen undergoing a transition to early, poorly-developed apocrine metaplasia (blue arrow). Hyperplasia with moderately-developed apocrine metaplasia (yellow arrow) is seen to transition from the poorly-developed apocrine metaplasia. The focus at the yellow arrow looks very similar to the previous concerning focus. As such, the previously shown concerning focus was interpreted as benign hyperplasia with apocrine metaplasia.
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Same IDP as above, blue and black arrows. 400x.
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Same IDP as above, yellow arrow. 400x.
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Apocrine DCIS involving an IDP. 20x.
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Same tumor as above. 40x. A portion of IDP is present on the left side of the figure. An expansive proliferation is present on the right side of the figure. Necrosis is present.
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Same tumor as above. 40x. The proliferation involves large areas of the lesion.
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Same tumor as above. 100x. Extensive necrosis involves the lesion.
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Same tumor as above. 200x. The epithelial proliferation shows no transition from a benign proliferation, and no transition to a well-developed apocrine proliferation. The cells contain abundant pink cytoplasm, as is seen in apocrine DCIS.
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Same tumor as above. 400x. The proliferation is composed of low-grade, monomorphic cells with abundant pink cytoplasm. Convincing polarization of cells is seen (left side of figure).
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Same tumor as above. 100x. In this focus, both benign IDP (left side of figure) and the atypical cellular proliferation (right side of figure) are seen. No transition from a benign proliferation is present.
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Same tumor as above. 200x. Higher power examination confirms the lack of transition from a definite benign proliferation, and shows cellular monomorphism.
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Same tumor as above. 100x. Foci of comedo necrosis are identified.
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