To investigate the characteristic sonographic and pathological features of breast ductal carcinoma in situ (DCIS) without microcalcifications on mammography (MG).

Forty cases of DCIS without microcalcifications on MG were retrospectively reviewed. The 40 lesions were classified into mass and non-mass groups according to their sonographic findings. The pathological subtypes and nuclear grades of these cases were also analyzed. Fisher exact test was used to compare the differences of the sonographic accuracy rate, sonographic microcalcification rate, pathological nuclear grade and subtype rate between mass and non-mass groups.

No abnormal finding was found in sixteen cases (40.0%) on MG and only one case (2.5%) on ultrasonography (US), respectively. The most common sonographic feature of DCIS without microcalcifications on MG were masses (75.0%, 30/40), and other sonographic findings were round/oval and irregular shape, microlobulated margin, heterogeneous hypoechogenicity and isoechogenicity, and posterior acoustic feature. Ductal dilatations and heterogeneous isoechogenicity were present in most non-mass lesions of DCIS without microcalcifications on MG (22.5%, 9/40). The ultrasonographic microcalcifications were found in 5 cases of DCIS without microcalcifications on MG. The common pathological features of DCIS without microcalcifications on MG were medium-low nuclear grade (85.0%, 34/40) and noncomedo (87.5%, 35/40). The difference of US accuracy rate in mass and non-mass groups was statistically significant [73.3% (22/30) vs 33.3% (3/9), P=0.047]. The differences of US microcalcification rate, pathological subtype and nuclear grade were not significant (P=1.000, 0.070).

The mass appearance and medium-low nuclear grade were most common sonographic findings and pathological features of DCIS without microcalcifications on MG. Ultrasonography should be an helpful tool for improving the diagnostic sensitivity of mammography in breast DCIS.