Utility of mapping lymph nodes cleared from rectal adenocarcinoma specimens

The lymph node clearing technique improves the detection of lymph nodes in colorectal cancer specimens. The purpose of this study was to determine the utility of mapping the lymph nodes cleared from rectal adenocarcinoma specimens by evaluating the possible relationship between the pattern of lymph node metastases to the site of the recurrent disease. A retrospective medical record review was performed in 40 patients with primary rectal adenocarcinoma. The specimens were analysed by lymph node clearing technique and mapped after surgery. The lymph nodes were mapped according to their location in the cleared specimens. Statistical analysis was performed using the chi 2-test. A total of 1290 lymph nodes were cleared in 40 specimens. Of these, 1126 (87%) lymph nodes were < or = 5 mm. One-hundred and ten (9%) lymph nodes were metastatic. Sixty-seven (61%) of these 110 lymph nodes were 5 mm or less in size. The majority of lymph nodes with or without metastases were in the pelvis, as opposed to an extrapelvic location (P = 0.0001). Eleven patients recurred. In nine of these patients the recurrence showed a direct relationship between the level of metastatic lymph node location (pelvic vs. extrapelvic) and the site of the recurrent disease (loco-regional or systemic, P = 0.05). The majority of lymph nodes, both normal and metastatic, cleared from specimens from rectal adenocarcinoma were < or = 5 mm in diameter. The lymph node mapping technique may help in predicting the site of recurrence.