Background: Amplification of keratin 19 mRNA (K19) by reverse transcriptase-polymerase chain reaction (RT-PCR) has been shown to be a sensitive method to detect occult breast cancer metastases in lymph nodes.
Methods: Axillary lymph nodes were obtained from 126 patients with breast cancer, and metastases in these lymph nodes were studied by both histologic examination and K19 RT-PCR. The patients were categorized into 3 groups according to the results of these 2 examinations, i.e., patients with 1) both histologically and K19 RT-PCR negative lymph nodes (metastases negative group [n = 91]); 2) histologically negative but K19 RT-PCR positive lymph nodes (occult metastases positive group [ n = 15]); and 3) histologically positive lymph nodes (metastases positive group [n = 20]).
Results: Various histologic parameters such as tumor size, histologic type, histologic grade, lymphatic invasion, vascular invasion, and estrogen receptor status were compared among these three groups. There were no significant differences among any of these histologic parameters between the metastases positive and occult metastases positive groups. Conversely, tumor size of the metastases positive (2.5 +/- 0.2 cm) and occult metastases positive (2.5 +/- 0.2 cm) groups was significantly (P < 0.05) greater than that of the metastases negative group (1.9 +/- 0.1 cm), and positivity of lymphatic vessel invasion in the former 2 groups (70% and 53%, respectively) was also significantly (P < 0.01) greater than that in the latter group (18%).
Conclusions: These results demonstrate that histologic characteristics of breast cancers with occult metastases are similar to those of breast cancers with histologically detectable metastases.