[1072] Low-Grade “Ovarian” Serous Carcinomas Are Derived Mainly from the Fallopian Tube.

Beihua Kong, Nisreen AbuShahin, Li Xiang, Oluwole Fadare, Wenxin Zheng. University of Arizona Collage of Medicine, Tucson; Qilu Hospital Shandong University, Jinan, Shandong, China; Vanderbilt University School of Medicine, Nashville, TN

Background: Ovarian serous carcinoma can be broadly categorized into two clinicopathologically distinct groups: high- and low-grade. A significant subset, and possibly the majority, of high grade serous carcinomas are presently thought to originate in the fallopian tube. However, the cell of origin of their low grade counterparts is presently unclear. We compared the phenotypes of ovarian surface epithelia (OSE), ovarian epithelial inclusion cysts (OEIs) and low-grade serous carcinomas (LG-Ca) in order to test the hypothesis that LG-Ca have a tubal, rather than ovarian surface epithelial phenotype
Design: 98 benign ovaries, 50 fallopian tubes, 48 serous cystadenomas, 42 serous borderline tumors, and 28 low-grade serous carcinomas, including the OSE and OEIs of the benign ovaries, were studied by immunohistochemistry using antibodies to PAX8, Calretinin, Ki-67, and tubulin. The secretory to ciliated cell ratio (S/C) was also calculated for each case.
Results: See Table 1.

Secretory and ciliated cells

Features	OSE	OEI	FT	Cystadenoma	Bordeline tumor	LG-CA
S/C ratio∧	<0.0001	3.8 +/- 1.1	1.2 +/- 0.5	7 +/- 3.2	35 +/- 12	98 +/- 1.2
PAX8	2/48 (4%)	256/261 (98%)	50/50 (100%)	48/48 (0%)	42/42 (100%)	28/28 (100%)
Calretinin	48/48 (100%)	4/261 (2%)	0/50 (0%)	0/48 (0%)	0/42 (0%)	0/28 (0%)
Tubulin*cells	2 +/- 1.8%	48 +/- 15%	75 +/- 16%	41 +/- 20%	22 +/- 10%	5 +/- 2.3%
ki-67**index	<1%	4 +/- 1.2%	8 +/- 3.5%	5 +/- 2.1%	15 +/- 4.8%	32 +/- 12%

^S/C ratio based on H&E findings. *Tubulin stains ciliated cells, which was presented as an average of sum of all cases studied. **The numbers represent the average Ki-67 index for all cases studied. Cystadenoma, borderline tumor and LG-Ca diagnosed as ovarian based on conventional criteria


Conclusions: The immunophenotype of LG-Ca, OEIs, and normal tubal epithelium, are similar, and are notably different from the immunophenotype of OSE. This suggests that LG-Ca are ultimately tubal in origin. Differential patterns of tubulin expression between tubal epithelium and LG-Ca cells suggest that the cancer develops from a clonal expansion of tubal secretory cells, although detailed mechanisms underlying this process remain unclear. Alternatively, LG-Ca may arise through the direct implantation of tubal epithelium onto the ovary to form OEIs, from which the cancer develops.
Category: Gynecologic & Obstetrics

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 134, Wednesday Morning