Intratumoral versus intraparenchymal injection technique for lymphoscintigraphy in breast cancer.

A 1.5-cm nonpalpable mass was detected in the upper outer quadrant of the left breast by screening mammography in a 55-year-old woman. The patient was scheduled for a sentinel node procedure, and lymphoscintigraphy was performed the day before surgery. Unintentionally, she received an intraparenchymal tracer injection 3 cm away from the malignant lesion instead of the intended intratumoral injection. Lymphoscintigraphy revealed two sentinel nodes in the axilla. A second dose of Tc-99m nanocolloid was injected the next day into the primary tumor through a catheter that had been inserted under ultrasound guidance the previous day. Once more, a lymphoscintigraphic image was obtained that showed additional sentinel nodes in two different regions outside the axilla. This observation supports the authors' contention that lymphatic watersheds exist in the breast and highlights the importance of tracer administration into or close to the tumor.