Ovarian Low-grade Serous Carcinoma: A Clinicopathologic Study of 33 Cases With Primary Surgery Performed at a Single Institution.

Ovarian low-grade serous carcinoma (LGSC) is an entity with distinct pathologic and clinical features. The number of studies on this type of tumor is limited. In this article, we present our experience with 33 cases of ovarian LGSC with primary surgical treatment at our institution. For comparison, a cohort of ovarian high-grade serous carcinoma (HGSC) was also studied. Clinical information was obtained from the patients' charts or from the treating physicians. Hematoxylin and eosin slides were reviewed of 28 available LGSCs, and the following parameters were recorded: presence/absence of a serous borderline tumor (SBT), presence/absence of micropapillary/cribriform pattern (MP/CP), architectural pattern in the invasive component, and presence/absence of desmoplasia or fibrosis. The incidence of ovarian LGSC was 4.7%. LGSC patients ranged in age from 19 to 79 years (mean, 52 y), with 21.2% younger than 40 years. HGSC patients ranged in age from 38 to 90 years (mean, 62 y), with 1.6% younger than 40 years. LGSCs were staged as follows: stage I (2), stage III (23), and stage IV (8). Twenty-eight of 33 LGSC cases had concurrent SBT, with this component accounting for >50% of the neoplasm in 15 cases. In addition, MP/CP was noted in 19 cases. Invasion patterns included micropapillae (93%), cribriform nests (74%), elongated papillae (26%), glandular (44.4%), medium-sized papillae (33.3%), solid nests (22.2%), macropapillae (19%), and single cells (19%). In addition, desmoplasia (44.4%) and fibrosis (37%) were noted. Follow-up data ranging from 13 to 195 months (median 61.2 mo) were available on 30/33 LGSC patients: 18 (60%) were dead of disease; 1 (3.3%) was dead of other cause; 5 (16.7%) were alive with disease; and 6 (20%) had no evidence of disease. Follow-up data from 1 to 169 months (median 48 mo) were available on 185 HGSC patients: 132 (71.4%) were dead of disease; 3 (1.6%) were dead of other cause; 21 (11.4%) were alive with disease; and 29 (15.7%) had no evidence of disease. Ovarian LGSC is rare with a predilection for younger patients relative to HGSC. Most LGSC cases are associated with SBT with an MP/CP, and their invasive component usually contains a micropapillary pattern. Most patients with ovarian LGSC present with advanced-stage disease and have a short-term survival advantage over patients with HGSC (estimated 5 y survival: 62.3% vs. 43.9%). However, over a prolonged period of time, this survival advantage decreases (estimated 10 y survival: 21.2% vs. 22.7%).