What is papilloma with atypia (atypical papilloma)?

Updated: Jun 18, 2020
  • Author: Oudai Hassan, MD; Chief Editor: Chandandeep Nagi, MD  more...
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Although intraductal papillomas (IDPs) are benign, they are occasionally involved by a monomorphic, atypical cellular proliferation, morphologically identical to ductal carcinoma in situ (DCIS) or atypical ductal hyperplasia (ADH). Specific terminology for this differs among authorities. Some diagnose atypical papilloma (also known as papilloma with atypia) if the monomorphic cellular proliferation is smaller than 3 mm in greatest dimension and is low grade, and diagnose DCIS involving a papilloma if the proliferation is 3 mm or larger or is intermediate to high grade. [1, 2] Others advocate the diagnosis of DCIS involving a papilloma irrespective of the size and grade of the atypical cellular proliferation. [3]

Large/central IDP subtypes (L/C ST) may be involved by complex, crowded benign cellular proliferations involved by varying degrees of apocrine metaplasia, which can mimic the histologic features of DCIS (see Microscopic Findings). These lesions are difficult to evaluate, and examination of the entire lesion may be required to distinguish them from DCIS involving a papilloma. Given this, the material afforded by core needle biopsy (CNB) may be insufficient to make a confident diagnosis.

Several studies have shown IDPs involved by suspicious cellular proliferations seen on CNB are more commonly associated with cancer upon excision than IDPs without atypia diagnosed on CNB (see Prognosis and Predictive Factors). As such, the term atypical papilloma may refer to an IDP sampled on CNB with features suspicious for DCIS involving an IDP.

For the purposes of this article, the term "DCIS involving a papilloma" is used to describe an IDP involved by a cytologically malignant cell population, regardless of the size of the proliferation. "Atypical papilloma" is used to describe an IDP seen on CNB that is involved by a proliferation that has features suspicious for DCIS involving a papilloma, and therefore requires excision for a more definitive diagnosis.

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