Mammographically detected spicules associated with malignant breast tumors frequently harbor additional tumor foci

Abstract

Background: On imaging, malignant breast masses are commonly associated with spicules. To the best of our knowledge, the clinical significance of such spiculae has not been previously studied, and no surgical guidelines are available for the management of mammographically detected spiculations.

Patients and methods: Between April 2018 and December 2019, all consecutive breast-conserving surgery -patients with invasive malignant lesions, who required intraoperative radiological breast specimen assessment with tomosynthesis, were retrospectively included in this analysis. The tumors were classified into two groups: those with spiculated margins as the dominant feature, and those with other distinct morphological characteristics. Spicule visualization, length, and distribution were evaluated in both groups using pre- and intraoperative imaging and compared with the histopathological features of the spicules.

Results: In total, 162 invasive lesions were evaluated. The presence of spicule-associated additional tumor foci was a common finding; 67.6% of the spiculated tumors and 48.9% of the other tumors had additional foci. Most additional tumor foci were within 1 cm of the tumor edge. The mean pathologically measured distance from the main tumor margin to the spicule-associated additional tumor foci was 4.3 ± 2.8 mm. Compared to the maximum spicule length determined from intraoperative images (9.5 ± 5.1 mm), the distance of actual tumor infiltration was much shorter, and a very weak correlation was observed.

Conclusions: Breast tumor spicules harbor additional tumor foci, which may lead to margin positivity and potential reoperation. Additional research is necessary to determine the actual tumor burden and clinical significance of spicules.

Keywords: breast cancer; breast conserving surgery; margin assessment; spicule.

Figure 1.

A 14 mm spiculated invasive ductal carcinoma (IDC) excised en bloc with spiculations. A tomosynthesis specimen radiogram at the level of the tumor documents the total removal of both the guidewire localized tumor (A; arrow) and the associated spicules (arrowheads). The histopathological analysis (B, H&E; 10 × magnification) showed that all the spicules contained additional tumors: the spicule shown in the red box contained IDC (100 × magnification); one spicule contained ductal carcinoma in situ (DCIS) (blue box, 150 × magnification); other spicules contained both DCIS and IDC in green (100 × magnification) and yellow (150 × magnification) boxes.

Figure 2.

A mammogram of a nonpalpable, spiculated 12 mm invasive ductal carcinoma: a craniocaudal-tomosynthesis view (A) demonstrates spiculations better than full-field digital mammography in mediolateral-projection (B). After breast conserving surgery, a more superficial axial section (C) the invasive additional cancer extends 2.2 mm from the tumor’s margin. In the deeper section (D) additional invasive cancer cells are visible further in the spicule extending up to 2.7 mm from the tumor’s margin highlighting that analyzing only one section of a spicule will underestimate the extent of the disease. (E) A magnified view of the base of the spicule.

Figure 3.

(A) A mediolateraloblique spot magnification view of a 13 mm mainly circumscribed, mixed papillary and invasive ductal carcinoma (arrows) with a few spicules (arrowheads). The histopathologal analysis (B) showed a single solid spicule with multiple foci, likely representing a continuum of low-grade ductal carcinoma in situ (arrows) extending as far as 10.1 mm from the tumor’s edge and close to the resection margin.