Comedo-type ductal carcinoma in situ

Last revised by Mohammad Taghi Niknejad on 24 Feb 2023

A comedo-type ductal carcinoma in situ, also known as comedocarcinoma in situ, is a high grade subtype of ductal carcinoma in situ (DCIS). It is the most aggressive of intraductal carcinomas. In 30% of cases it can be multicentric and/or multifocal.

Comedo-type DCIS is diagnosed histologically when at least one duct in the breast is filled and expanded by large, markedly atypical cells. 

Comedo-type DCIS completely fills and dilates the ducts and lobules of the terminal duct lobular units (TDLU) with plugs of high grade tumor cells with pleomorphic nuclei and central necrosis ("comedonecrosis"). 

Infiltrating ductal carcinoma (infiltrative ductal carcinoma with central necrosis) may so closely mimic the pattern of DCIS with central comedonecrosis that on initial morphological analysis these foci of tumors are often labeled as DCIS (high grade, comedo-type).

There is a risk of occult infiltration. A comedo that extends for >2.5 cm has an invasive component in 45% of cases.

Casting-type microcalcifications are the most frequent mammographic finding (78% of cases) in comedo-type DCIS. Calcifications may be grouped or fine-linear branching.

As with DCIS in general, it appears as linear or segmental clumped non-mass enhancement.

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Cases and figures

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