We tried to determine the significance of invasion to the muscularis mucosae on the progression and recurrence of the superficial bladder cancer. Muscularis mucosae was composed of the smooth muscle bundles around relatively large vessels and
found
in
the lamina propria, approximately midway between the surface mucosa and the true muscular layer, lying parallel to the mucosa.
Between January 1984 and December 1993, 81 patients with diagnosed superficial bladder cancer showing lamina propria invation (pT1) were treated by transurethral resection (TUR) at our hospital. the mean age was 59.4 years (range, 31-86 years),
the
mean
follow-up period was 35.3 months (range, 13-120 months) and the male : female ratio was 69:12.
We subclassified superficial bladder cancer showing lamina propria invasion into two groups, with (pTlb) or without (pT1a) cancer invasion ot the muscularis mucosae. The muscularis mucosae was identified in 58 (71.6%) of 81 cases. In the other
cases
(28.4%), relatively large vessels were used as the landmark instead of the muscularis mucosae. Of 81 bladder cancers, 52 (64.2%) were diagnosed as pT1a and 29 (35.8%) as pT1b. The progression rate of pT1b cancer (41.4%) was significantly higher
than
that of pT1a cancer (3.8%) (p=0.001). And the recurrence rate of pT1b cancer (55.2%) was significantly higher than that of pT1a cancer (26.9%) (p=0.024).
In conclusion, superficial bladder cancer invading to the muscularis mucosae has a high risk for disease progression after TUR. Careful follow-up examination and aggressive therapy should be recommended in patients with these tumors.
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