Adult Granulosa Cell Tumor

This case first appeared as Performance Improvement Program in Surgical Pathology (PIP) 2021, Case 39, and is adult granulosa cell tumor in the ovary.

The information provided in this case was accurate and correct at the time of publication in 2021.

Any changes in terminology since the time of publication may not be reflected in this case.

Microscopic sections demonstrate a cellular lesion with a diffuse growth pattern showing a “watered silk” appearance at low power with cysts present on the periphery. High-power magnification demonstrates epithelioid cells with round to ovoid nuclei with longitudinal grooves. They have fine chromatin and conspicuous nucleoli. There is minimal cytologic atypia, and mitosis are fewer than 5/10 high-power fields (HPF). These findings are diagnostic of adult granulosa cell tumor (AGCT).

AGCT account for approximately 2% of malignant ovarian tumors and have an average age of presentation of 50 years old. Most present as large unilateral adnexal masses, on average 12 cm. Clinical manifestations of hyperestrogenemia occur in up to two-thirds of cases, and menometrorrhagia or postmenopausal bleeding may be the presenting symptom. The estrogenic excess can less commonly manifest as endometrial hyperplasia or endometrioid adenocarcinoma (fewer than 5% of patients with AGCT). Symptoms of androgen excess may occur in up to 10% of cases, primarily as secondary amenorrhea. Most tumors (95%) are Stage 1 at presentation. Some present with hemoperitoneum secondary to tumor rupture, which may be a helpful clinical clue encountered at the time of frozen section. The most important prognostic factor is stage, with decreasing 5-year overall survival in advanced cases. AGCT may recur up to decades later, and thus lifelong surveillance is important for patients.

AGCT is a proliferation of granulosa cells in the background of fibrothecomatous ovarian stroma. Several growth patterns may simultaneously occur. The most common type is diffuse, followed by trabecular, microfollicular (with pathognomonic Call-Exner bodies), macrofollicular, insular, and gyriform or watered silk patterns. Cystic AGCT can demonstrate Call-Exner bodies associated with tumor cell nests in the cyst wall, which can be easily overlooked. The cells have scant eosinophilic cytoplasm with oval nuclei that demonstrate longitudinal grooves. Most often, the chromatin pattern is fine, and nuclei can have variable nucleoli.

AGCT express markers of sex cord differentiation, including inhibin, calretinin, SF1, and FOXL2 by immunohistochemistry (IHC). While FOXL2 IHC positivity is nonspecific, FOXL2 c.402C>G somatic mutations are more specific (found in approximately 95% to 97% of cases). Recently, TERT promoter mutations have been identified in recurrent AGCT while absent in their original primary, implicating their role in progression of AGCTs.

Keratin immunohistochemical staining can be variably positive and can be used as a tool when the differential diagnosis is between a luteinized AGCT and a thecoma. In these cases, aggressive sampling of the periphery and keratin staining can help identify granulosa cells to support the diagnosis of luteinized AGCT over thecoma.

Fibroma is one of the most common sex cord-stromal tumors. Cellular fibromas are more common in the differential diagnosis for AGCT and are typically 8 to 9 cm on average. Cellular fibromas may have a diffuse growth pattern but often have areas of storiform growth. Tumor cells are basophilic and spindled, with oblong nuclei that lack grooves. Reticulin can be particularly helpful because it is not nested, as in AGCT, but is instead pericellular. By IHC, WT1, FOXL2, and SF1 are positive; rarely inhibin and calretinin may have focal positivity. Fibromas lack FOXL2 mutations.

Reticulin staining can be helpful in diagnosing AGCT, particularly in luteinized AGCT in a fibrous stroma when considering a thecoma in the differential diagnosis. In thecomas, reticulin stain highlights reticulum fibrils wrapping individual theca cells, while in AGCT the reticulum fibrils surround nests or clusters of cells. Caution should be used in interpreting reticulin, because many sex cord-stromal tumors may demonstrate a fibrothecomatous stroma that can become luteinized, but they should have reticulin surrounding individual cells. Correlating reticulin staining with nested areas on H&E sections is critical, and molecular testing for FOXL2 mutations is often required in challenging cases.

Endometrioid adenocarcinoma with sex cord-like differentiation has cords and trabeculae of tumor cells in a background of hyalinized stroma. The background stroma may be luteinized. It often is associated with endometriosis, and sampling may help to identify areas with squamous or mucinous differentiation. IHC is helpful in differentiating these entities; endometrioid adenocarcinoma should express CK7, EMA, and PAX8, without expression of inhibin or SF1.

Juvenile granulosa cell tumor (JGCT) accounts for 5% of all granulosa cell tumors. They often occur in younger women under the age of 30 and may present with precocious puberty due to their hormonal effects. They are typically large unilateral masses (5 to 15 cm) that have a solid and cystic cut surface. The parenchyma may be soft to indurated and is yellow to white in appearance. On microscopic examination, they typically have a diffuse architecture with irregular follicles dispersed throughout. The follicles are lined by granulosa cells, which have abundant eosinophilic cytoplasm and round nuclei with variable atypia. Their nuclei almost uniformly lack grooves. Mitotic figures are frequent. They are positive for inhibin, calretinin, WT1, FOXL2, and keratin and have retained SMARCA4 (BRG1). They lack FOXL2 mutations.

Small cell carcinoma, hypercalcemic type is an aggressive tumor that usually occurs in the second or third decade of life. They present as large unilateral masses, on average 15 cm. As the name implies, hypercalcemia is a frequent finding due to parathyroid hormone-related peptide production by tumor cells. It most often demonstrates a diffuse growth pattern, but cells may be nested, corded, trabecular, or single file. Necrosis is common. Glands or cysts can be lined by mucinous epithelium, and the intervening stroma may be edematous, myxoid, or hyalinized. At the periphery, vascular invasion is often present, as well as adjacent soft tissue involvement. Cytologically, both large and small cell components can be seen. Small cells are round with scant cytoplasm, hyperchromatic nuclei, and small nucleoli. The larger cell component has abundant eosinophilic cytoplasm, large nuclei with a vesicular chromatin pattern, and prominent nucleoli. Mitotic activity is usually brisk. They have mutations in SMARCA4, which can be inferred by aberrant loss of SMARCA4 (BRG1) IHC staining in most cases. The tumor cells are often positive for CAM5.2, p16, and calretinin but negative for inhibin. Abnormal (mutant) p53 expression can also be seen.

Steroid cell tumors are typically well circumscribed and unilateral large tumors, 8 cm on average. They most often have a diffuse growth pattern but can have small nests of tumor cells. The cells are polygonal or round with distinct cellular borders and have abundant eosinophilic or clear cytoplasm. Their nuclei are centrally located with prominent nucleoli. Stroma is not a frequent feature but can be fibromatous or edematous when present. They typically stain positive for inhibin and calretinin, with infrequent keratin expression. They lack FOXL2 mutations.

1. Which is the most specific diagnostic test for adult granulosa cell tumors (AGCT)?
   
   
   1. Negative inhibin immunohistochemical (IHC) stain
   2. Positive FOXL2 c.402C>G mutation
   3. Positive FOXL2 IHC stain
   4. Positive keratin IHC
   5. Positive SMARCA4 mutation
2. Which immunophenotype is correct for small cell carcinoma, hypercalcemic type?
   
   
   1. Block-like p16 staining
   2. Loss of SMARCA4 (BRG1) staining
   3. Negative keratin staining
   4. Positive inhibin staining
   5. Positive WT1 staining
3. Which of the following is associated with poor prognosis in AGCT?
   
   
   1. High stage
   2. Mitoses <5/10 HPF
   3. Premenopausal patients
   4. Size <5 cm
   5. Young age

1. Burandt E, Young RH. Thecoma of the ovary: a report of 70 cases emphasizing aspects of its histopathology different from those often portrayed and its differential diagnosis. Am J Surg Pathol. 2014;38(8):1023-1032.
2. Chapter 16, Sex cord-stromal and steroid cell tumors of the ovary 501-540. In: Clement PB, Stall JN, Young RH, eds. Atlas of Gynecologic Surgical Pathology. 4th ed. Elsevier. 2020:501-540.
   
3. Guerrieri C, Frånlund B, Malmström H, Boeryd B. Ovarian endometrioid carcinomas simulating sex cord-stromal tumors: a study using inhibin and cytokeratin 7. Int J Gynecol Pathol. 1998:17(3):266-271.
4. Pilsworth JA, Cochrane DR, Xia Z, et al. TERT promoter mutation in adult granulosa cell tumor of the ovary. Mod Pathol. 2018:31(7):1107-1115.
5. Stall JN, Young RH. Granulosa cell tumors of the ovary with prominent thecoma-like foci: a report of 16 cases emphasizing the ongoing utility of the reticulin stain in the modern era. Int J Gynecol Pathol. 2019;38(2):143-150.
6. Young RH. Ovarian sex cord-stromal tumours and their mimics. Pathology. 2018:50(1):5-15.
7. Young RH, Prat J, Scully RE. Ovarian endometrioid carcinomas resembling sex cord-stromal tumors. A clinicopathological analysis of 13 cases. Am J Surg Pathol. 1982;6(6):513-522.

1. Positive FOXL2 c.402C>G mutation (b)
2. Loss of SMARCA4 (BRG1) staining (b)
3. High stage (a)