Serous tumor of low malignant potential with early stromal invasion (serous LMP with microinvasion).

Eighteen examples of serous carcinoma arising in a background of a serous tumor of low malignant potential (SLMP with microinvasion) are reported. Nine of the 18 patients were less than 35 yr of age, and 5 were pregnant. In one patient, the microinvasive tumor was bilateral. The contralateral ovary had a serous tumor of low malignant potential (SLMP) in 9 additional women. Twelve patients presented with Stage I tumors, while 6 (33%) had tumors in Stages II and III. The tumors in all patients below the age of 30 were Stage I, and all three patients with Stage III tumors were older than 50. Two cell types were identified in all 18 tumors. The more dominant cell type was similar to those found in the typical SLMP tumors. The second cell type was larger with abundant eosinophilic cytoplasm, round nuclei, and prominent nucleoli; these were the cells that invaded the stroma of the papillary stalks in every case. Only one patient died of her disease, and she had Stage III tumor with massive ascites at presentation. All other patients are alive and well without evidence of disease from 2.5 to 5.5 yr after the diagnosis.