Ductal carcinoma in situ (DCIS) is a heterogeneous process, divided into comedo and non-comedo types. The non-comedo subtypes include cribriform, micropapillary, and solid DCIS. DCIS is heterogeneous in biological behavior, histological appearance, and imaging findings. Because of this heterogeneity in biological behavior appropriate treatment has been controversial. The imaging findings associated with the micropapillary type of DCIS have not been extensively studied, due at least in part to the fact that pure, micropapillary DCIS is relatively uncommon. The article by Lee et al in this issue is an investigation into the imaging features of this tumor and the relative accuracy of determining extent of disease.
Pathologically, micropapillary DCIS is characterized by the presence of dilated ducts lined by a population of monotonous cells with small finger-like or club-shaped papillary fronds extending into the ductal lumen. The protuberances may form arches, which when present is a distinctive feature. This subtype of DCIS is associated with extensive disease as well as with multifocal and multicentric disease. When mixed micropapillary and cribriform types of DCIS are present, which is the most common situation, there is no special significance attached to the micropapillary forms.
Lee has assessed the imaging findings associated with this lesion and the clinical implications associated with this diagnosis. In their series of 41 patients, the majority of lesions were detected on screening. The findings on mammography are most often pleomorphic or amorphous calcifications with a segmental or regional distribution, findings that will prompt biopsy.
Ultrasound was found to be of limited value, with no ultrasound abnormality found in almost half of the 36 patients evaluated with sonography. The high false-negative rate is felt to be due at least in part to the fact that most of the lesions were screening detected rather than clinically detected, although it is possible that this subtype of DCIS may be sonographically occult even when extensive. In those cases where masses were found on ultrasound, these were hypoechoic with an irregular shape and angular margins, features more usually seen with invasive carcinomas.
Magnetic resonance imaging (MRI) was only performed in four cases, making it difficult to assess its usefulness in evaluating this subtype of DCIS. In those cases in which it was used, the findings were segmental or regional non–mass-like enhancement with clumped or heterogeneous internal enhancement. Additional study is needed to evaluate the role of MRI in this circumstance.
Both mammography and ultrasound were found to underestimate tumor size. Mammography underestimated tumor size in about one-third of the cases, and 80% of the cases were underestimated with ultrasound. MRI was found to be accurate for size estimation in those cases where it was used. Although the results of MRI are promising, the number of cases is too small to allow conclusions to be drawn regarding the utility of MRI in this situation.
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References
1. Lee YS, Mathew J, Dogan BE, et al. Imaging features of micropapillary DCIS: correlation with clinical and histopathological findings. Acad Radiol
2. Holland R., Hendriks J.H.: Extent, distribution and mammographic/histological correlations of breast ductal carcinoma in situ. Lancet 1990; 335: pp. 519-522.
3. Castellano I., Marchio C., Tomatis M., et. al.: Micropapillary ductal carcinoma in situ of the breast: an inter-institutional study. Modern Pathol 2010; 23: pp. 260-269.