Diffusely infiltrative endometrial adenocarcinoma: an adenoma malignum pattern of myoinvasion

The prognostic significance of a diffusely infiltrative intramyometrial growth pattern was evaluated in 110 cases of low-stage (stages I and II) endometrial adenocarcinoma. Fifty cases were associated with diffuse infiltration (DI group), and 50 cases had more conventional granulation tissue type intramyometrial infiltration (GTT group). Ten cases with carcinomatous involvement of deeply situated adenomyosis (ADMY group) were also studied. The diffusely infiltrative "adenoma malignum" growth pattern featured typically round, regular individual glands, clearly within myometrium but with minimal or absent stromal or inflammatory cell response. Myoinvasion of the conventional sort was characterized by irregular, sharply angulated abnormal glands within myometrium without interposed normal glands or endometrial stroma. The abnormal glands were surrounded, at least focally, by edematous stroma with granulation tissue type reaction and/or an inflammatory cell infiltrate. Mean follow-up was 77.8 months (range 3-219 months) for the patients with diffusely infiltrative myoinvasion and deep adenomyosis and 86.9 months (range 1-206 months) for the patients with conventional myoinvasion. Recurrence-free survival for patients with stage I disease and conventional myoinvasion (94%) was similar to that of patients with diffuse adenoma malignum infiltration (98%; p = 0.13). Survival rates for both groups were also similar. Two (4%) of the 50 patients with diffusely infiltrative adenoma malignum pattern of myoinvasion died of endometrial carcinoma 36 and 72 months after hysterectomy, and 2 (4%) of the 50 patients with conventional myoinvasion died 34 and 67 months after hysterectomy (p = 0.41). Survival in these patients correlated with depth of myometrial invasion and stage. There were no recurrences in the patients with deep adenomyosis. These results suggest that although endometrial carcinomas with diffuse myometrial infiltration are fully capable of aggressive clinical behavior, they do not appear to behave any more aggressively than those with conventional myometrial invasion. Prognostic indicators of clinically aggressive disease are similar to those that have been previously identified for endometrial carcinomas with the more conventional pattern of myometrial infiltration. They include cervical involvement, deep myometrial invasion, higher histologic grade, and lymph-vascular space invasion. Endometrial carcinomas with extensive involvement of adenomyosis and adjacent foci of minimal myometrial infiltration appear to have very low malignant potential, but the number of cases with this finding and adequate clinical follow-up is limited. This finding needs to be confirmed in a much larger series of cases.