Internal mammary lymphadenopathy in breast carcinoma: CT appraisal of anatomic distribution.

Internal mammary lymph nodes are an important site of occult metastasis in clinically operable and recurrent breast carcinoma. Anatomic distribution of enlarged internal mammary nodes in patients with breast cancer was analyzed in a review of thoracic computed tomographic studies of 219 women with operable, advanced, or recurrent cancer. Enlarged nodes were observed in 45 patients (20.5%), 32 with unilateral and 13 with bilateral involvement. Mean nodal diameter was 1.95 cm (0.6-6.0 cm). Lymphadenopathy was limited to one anterior intercostal space in 43%, two spaces in 26%, three spaces in 22%, and four spaces in 9%. Solitary or dominant nodal enlargement was centered at the first space in 14%, second space in 60%, and third space in 26%. Isolated lymphadenopathy in the fourth or fifth spaces was not observed. Metastases to internal mammary nodes frequently occur at multiple levels and are most common in the second and third spaces. This finding concurs with current surgical practice when internal mammary nodes are sampled.