Regional micrometastasis of low rectal cancer in mesorectum: a study utilizing HE stain on whole-mount section and ISH analyses on tissue microarray

AIM

To investigate the regional spread of microscopic tumor nodules in the mesorectum of patients with low rectal cancer, and to provide further pathological evidence for optimal procedure selection of radical resection for rectal cancer.

METHODS

Sixty-two patients with low rectal cancer underwent low anterior resection and total mesorectal excision (TME). Surgical specimens were sliced transversely on serial embedded blocks at 2.5-mm intervals, and stained with hematoxylin and eosin (HE). On whole-mount sections the mesorectum was divided into 3 regions: the outer region of the mesorectum (ORM), the middle region of the mesorectum (MRM), and the inner region of the mesorectum (IRM). Microscopic metastatic foci were investigated for metastatic mesorectal region, frequency, types, involvement of the lymphatic system, and correlation with the primary tumor. Tumor-suspect nodules previously considered disease free by HE stain on whole-mount section were examined by in situ hybridization (ISH) on tissue microarray (TMA) through detecting mRNAs of CEA and CK20 with non radioactive biotin-tagged oligonucleotide probes.

RESULTS

Microscopic spread of the tumor was observed in 50.0 percent of patients (31 out of 62, 24 by HE stain on whole-mount section and 7 by ISH on TMA) and that in the ORM was observed in 38.7 percent of the patients (24 out of 62, 16 observed by HE stain on whole-mount section and 8 by ISH on TMA). Microscopic tumor foci spread in the circumferential resection margin (CRM) occurred in 8.1 percent of the patients (5 out of 62, 4 observed by HE stain on whole-mount section and one by ISH on TMA), and distal mesorectum (DMR) involvement was detected in 6.5 percent (4 out of 62, all observed by HE stain on whole-mount section), with the spread extending to within 3 cm from the lower margin of the tumor. Most (26 of 31) of the patients with microscopic spread in mesorectum had TNM Stage III diseases.

CONCLUSIONS

The results of the present study support the theory that complete excision of the mesorectum without destruction of the ORM is essential for surgical management of low rectal cancer, and an optimal DMR clearance resection margin of no less than 4 cm was referenced. Five patients with microscopic tumor nodule spread in the CRM observed in the study suggested that microscopic metastases exist in pelvic lateral areas and in the mesorectum simultaneously, indicating the significance of preoperative and/or postoperative radiochemotherapy.

Microscopic spread of low rectal cancer in regions of the mesorectum: detailed pathological assessment with whole-mount sections

BACKGROUND AND AIMS

The aim was to investigate the regional spread of microscopic tumor nodules in the mesorectum of patients with low rectal cancer, and to provide further pathological evidence for optimal procedure selection of radical resection for rectal cancer.

PATIENTS AND METHODS

Sixty-two patients with low rectal cancer underwent low anterior resection and total mesorectal excision (TME). Surgical specimens were sliced transversely on serial embedded blocks at 2.5-mm intervals, and stained with hematoxylin and eosin. On whole-mount sections the mesorectum was divided into three regions: the outer region of the mesorectum (ORM), the middle region of the mesorectum (MRM), and the inner region of the mesorectum (IRM). Microscopic metastatic foci were investigated for metastatic mesorectal region, frequency, types, involvement of the lymphatic system, and correlation with the primary tumor.

RESULTS

Microscopic spread of the tumor was observed in 38.7% of patients (24 out of 62) and that in the ORM was observed in 25.8% of the patients (16 out of 62). Microscopic tumor foci spread in the circumferential resection margin (CRM) occurred in 6.5% of the patients (4 out of 62), and distal mesorectum (DMR) involvement was detected in 6.5% (4 out of 62), with the spread extending to within 3 cm from the lower margin of the tumor.

CONCLUSIONS

The results of the present study support the theory that complete excision of the mesorectum without destruction of the ORM is essential for surgical management of low rectal cancer, and an optimal DMR clearance resection margin should be no less than 4 cm. Four patients with microscopic tumor nodule spread in the ORM observed in the study suggested that microscopic metastases exist in pelvic lateral areas and in the mesorectum simultaneously, indicating the significance of preoperative and/or postoperative radiochemotherapy.

Prognostic significance of extranodal microscopic foci discontinuous with primary lesion in rectal cancer

PURPOSE

The most common recurrence after curative resection of rectal carcinoma originates from tiny, undetectable residual foci within the pelvic cavity. The significance and methods used to predict the presence of extramural and extranodal microscopic cancer foci discontinuous with the main lesion of rectal cancers were investigated.

METHODS

Four hundred twenty-seven patients who underwent resection of rectal carcinoma were studied. All resected specimens were examined for histologic evidence of extramural cancer separate from the main lesion.

RESULTS

Extramural cancers not in continuity with the main rectal lesion were classified as follows: 1) extranodal microscopic cancers; 2) large tumor nodules; 3) lymph node metastases. Each classification was found to influence long-term prognosis. Among them, microscopic cancer was thought to be especially relevant because, by virtue of its microscopic nature, it may be left in the pelvic cavity, causing local recurrence. The existence of large tumor nodules and metastatic lymph nodes correlated closely with the presence of microscopic cancer. Because large tumor nodules and lymph node metastases are possibly detectable during the operation by palpation and may be analyzed by microscopic frozen sections, they might be useful predictors of the presence of microscopic cancers.

CONCLUSIONS

In cases with extensive local rectal cancer spread, the nerve-sparing rectal resection that omits lateral dissection may be insufficient for local control because of incomplete removal of occult microscopic cancer, resulting in local recurrence. Presence of microscopic cancer correlates closely with large tumor nodules and metastatic lymph nodes. Intraoperative frozen section investigations may, thus, help in deciding on extent of location resection.

Synergistic effects of hyperthermia in preoperative radiochemotherapy for rectal carcinoma

PURPOSE

We investigated the effectiveness of hyperthermia added to preoperative radiation and chemotherapy for the treatment of rectal carcinoma.

METHODS

Forty-one patients receiving preoperative radiation were divided into two groups, Group A (20 patients; receiving radiation, hyperthermia, and chemotherapy) and Group B (21 patients, receiving no hyperthermia). Total dose of radiation was 40.5 Gy. Hyperthermia was administered using 8 MHz of radiofrequency. Rectal temperature reached 42 degrees C. A total dose of 3,400 mg of 5-fluorouracil given by suppository was used as the chemotherapeutic agent. Effect of the preoperative treatment was assessed by tumor reduction on barium enema, histologic findings of the resected specimens, area measurement of the residual cancer tissue, and by silver-staining nucleolar organizer region (AgNOR) score.

RESULTS

Tumor reduction on barium enema was significantly greater in Group A than in Group B (P < 0.01). Excluding two cases of mucinous carcinoma because a large acellular mucinous accumulation added materially to the cancerous area, the ratio of residual cancer area to total lesion size in Group A was significantly smaller than in Group B (P < 0.05). AgNOR score of the resected tumor tended to be smaller in Group A than in Group B.

CONCLUSION

Addition of hyperthermia resulted in a greater degree of tumor necrosis and was considered to be useful as a preoperative treatment for rectal carcinoma.