Lymphoscintigraphic Visualization of Internal Mammary Nodes With Subtumoral Injection of Radiocolloid in Patients With Breast Cancer

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Abstract
To determine whether subtumoral injection of radiocolloid is useful for lymphoscintigraphic visualization of the internal mammary node and in sentinel lymph node (SLN) biopsy of the axilla in breast cancer patients. The presence of retromammary lymphatics connecting to the axillary and internal mammary basins has been demonstrated by early anatomic studies. Thus, it is hypothesized that some lymph, especially that from the parenchyma under the tumor, may drain into both the axillary and internal mammary basins. Patients (n = 196) with T1-2, N0 breast cancer underwent preoperative lymphoscintigraphy with radiocolloid (technetium 99m tin colloid) injection into various sites of the breast, followed by SLN biopsy using the combined method with blue dye. Patients were divided into four groups: group A (n = 41), peritumoral injection of both radiocolloid and blue dye; group B (n = 70), periareolar radiocolloid and peritumoral blue dye; group C (n = 45), intradermal radiocolloid and periareolar blue dye; and group D (n = 40), subtumoral radiocolloid and intradermal blue dye. A retrospective analysis of 1,297 breast cancer patients who underwent extended radical mastectomy with internal mammary node dissection was also conducted to determine the relationship between vertical tumor location (superficial or deep) and frequency of axillary and internal mammary node metastases. One patient (2%) in group A, 3 (4%) in group B, 0 (0%) in group C, and 15 (38%) in group D exhibited hot spots in the internal mammary region on lymphoscintigraphy (P <.001, group D vs. the other groups). The concordance rate of radiocolloid and blue dye methods in detection of SLNs in the axillary basin was significantly lower in group D than in the other groups. In contrast, the mismatch rate (some SLNs were identified by radiocolloid and other SLNs were identified by blue dye, but no SLN was identified by both in the same patient) was significantly higher in group D than in the other groups. In patients treated with extended radical mastectomy, positivity of axillary and internal mammary metastases was significantly higher in patients (n = 215) with deep tumors than those (n = 368) with superficial tumors. These results suggest the presence of a retromammary lymphatic pathway from the deep portion of the breast to both axillary and internal mammary basins, which is distinct from the superficial pathway. Therefore, SLN biopsy with a combination of subtumoral and other (peritumoral, dermal, or areolar) injections of radiocolloid will improve both axillary and internal mammary nodal staging.