Low-grade serous carcinoma with solid growth pattern: an unusual architecture and potential pitfall

Low-grade serous carcinoma of the ovary is an uncommon lesion, composing approximately 3% of ovarian neoplasms. It typically arises in association with a serous borderline tumor and is most often at an advanced stage upon diagnosis. Gene mutations in BRAF and KRAS are characteristic. Various histologic architectural patterns are known, such as papillary, micropapillary, inverted micropapillary, glandular and nested. We report a case of low-grade serous carcinoma arising years after a serous borderline tumor and contralateral teratoma; the low-grade serous carcinoma showed two patterns: micropapillary growth and a previously unreported form of solid pattern manifesting as large tumor islands without slit-like spaces. This unusual solid morphology raises the differential diagnosis of high-grade serous carcinoma, which would result in different clinical management. The presence of areas with classic micropapillary architecture, in addition to the absence of high-grade cytonuclear atypia and marked pleomorphism, support the diagnosis of low-grade serous carcinoma. Immunohistochemical stains for p53 and p16 failed to show abnormal patterns characteristic of high-grade serous carcinoma. The patient declined chemotherapy and is on letrozole; she has had recurrent right pleural effusions over six months of follow-up after surgery.

Low-grade serous carcinoma; Ovary; Serous borderline tumor; Letrozole; Pleural effusion; Malignant

[1] WHO Classification of Tumours Editorial Board. Female genital tumours. 5th ed. WHO classification of tumours series. International Agency for Research on Cancer: Lyon. 2020.

[2] Ahn G, Folkins AK, McKenney JK, Longacre TA. Low-grade serous carcinoma of the ovary: clinicopathologic analysis of 52 invasive cases and identification of a possible noninvasive intermediate lesion. The American Journal of Surgical Pathology. 2016; 40: 1165–1176.

[3] Slomovitz B, Gourley C, Carey MS, Malpica A, Shih I, Huntsman D, et al. Low-grade serous ovarian cancer: state of the science. Gynecologic Oncology. 2020; 156: 715–725.

[4] Silva EG, Deavers MT, Malpica A. Patterns of low-grade serous carcinoma with emphasis on the nonepithelial-lined spaces pattern of invasion and the disorganized orphan papillae. International Journal of Gynecological Pathology. 2010; 29: 507–512.

[5] Quddus MR, Rashid LB, Hansen K, Sung CJ, Lawrence WD. High-grade serous carcinoma arising in a low-grade serous carcinoma and micropapillary serous borderline tumour of the ovary in a 23-year-old woman. Histopathology. 2009; 54: 771–773.

[6] Dehari R, Kurman RJ, Logani S, Shih I. The development of high-grade serous carcinoma from atypical proliferative (borderline) serous tumors and low-grade micropapillary serous carcinoma. American Journal of Surgical Pathology. 2007; 31: 1007–1012.

[7] Köbel M, Luo L, Grevers X, Lee S, Brooks-Wilson A, Gilks CB, et al. Ovarian carcinoma histotype. International Journal of Gynecological Pathology. 2019; 38: 353–362.