College of American Pathologists
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2008 —April Case of the Month

Updated April 4, 2008


CAP Foundation April 2008 Online Case of the Month

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After reading the summary, try answering the three related multiple-choice questions below.

A 24-year-old woman presented with abdominal pain. On examination, a left adnexal mass was palpated. Received was a 11 cm, 667 gm mass. On cut section, the tumor was yellow, predominantly solid, and had multiple small cysts containing hemorrhagic and mucoid material.

Archive Case and Diagnosis: This case first appeared as Performance Improvement Program in Surgical Pathology (PIP) 2005 Case 02 and is a yolk sac tumor (endodermal sinus tumor).

Criteria for Diagnosis and Comments: Yolk sac tumor of the ovary typically occurs in teenagers and young women. It commonly presents with abdominal pain and an adnexal or pelvic mass.

Gross Features: The tumors generally are unilateral, large (approximately 10-20 cm in greatest dimension,) solid and cystic. Only rarely are the tumors bilateral.

Microscopic Features: In your case, the tumor is composed of cysts and papillary projections lined by epithelioid cells with abundant, clear cytoplasm, prominent subnuclear vacuolization, scattered cytoplasmic eosinophilic hyaline bodies, moderate to severe nuclear atypia, and brisk mitotic activity up to 5 mitoses per single high power field. There are many Schiller-Duval bodies characterized by a fibrovascular core with typical perivascular epithelial formations. By immunohistochemistry, the tumor cells are alpha-fetoprotein and alpha-1-antichymotrypsin (+), CEA and Leu-M1 (-).

The original contributor (case submitted over 10 years ago) interpreted the histologic findings as those of a papillary cystadenocarcinoma of the ovary and sent the case for outside consultation. Consequent upon outside review and the performance of additional immunohistochemical studies, a diagnosis of yolk sac tumor was made. This highlights the difficulty encountered in the diagnosis of such cases.

Differential Diagnosis: The differential diagnosis generally includes ovarian surface epithelial tumors and other germ cell malignancies.

Germ cell tumors as a group typically occur in a young age group and are usually unilateral. The other malignant germ cell lesions differ morphologically from yolk sac tumor in that each typically exhibits specific histologic features. These include: cells with prominent single nucleoli and absence of any glandular/acinar differentiation (dysgerminoma); biphasic pattern of cyto- and syncytiotrophoblast (choriocarcinoma); and solid sheets and nests of primitive cells with multiple nucleoli (embryonal carcinoma). Typical immunostaining patterns for these are:

Yolk sac tumor: AFP(+),CDX-2(+),CD30(-), OCT3/4(-)
Choriocarcinoma: hCG(+), cytokeratin(+),OCT3/4(-)
Dysgerminoma: CD117(+),OCT3/4(+), D2-40(+), CD30(-)
Embryonal carcinoma: CD30(+), OCT3/4(+), D2-40(-), CD117(-)

The endometrioid and serous surface ovarian epithelial tumors may have a similar epithelioid appearance as yolk sac tumor but typically occur in older patients. Endometrioid carcinoma usually forms acini with a cribriform pattern or solid sheets with squamous differentiation. Serous tumors typically form tightly apposed papillae and slit-like spaces, or well-spaced papillary projections lined by stratified epithelium with marked nuclear atypia, and an appearance of detached, free-floating papillae. Psammoma bodies are typical in serous tumors, ranging from focal to abundant. Since many ovarian and serous tumors may have clear cell areas, evaluation of Wilms' tumor gene (WT-1) expression by immunohistochemistry may be useful since nuclear expression of WT-1 is reported in many serous tumors, and interestingly, also in adenomatoid tumors, but is absent in endometrioid and clear cell tumors as well as in yolk sac tumors. Secretory pattern type of endometrioid carcinoma could resemble yolk sac tumor; however, solid, cribriform and squamous areas, more typical of classic endometrioid carcinoma, can usually be found and unlike yolk sac tumor, is usually CK7(+).

Ovarian clear cell carcinoma, papillary pattern, is characterized by hyalinized papillae covered by polyhedral, cuboidal to flat cells with clear cytoplasm, hobnail cells, eccentric nuclei and positive immunostaining for CK7 and Leu-M1. Metastatic intestinal clear cell tumors may also have similar morphology, but, unlike EST, they are usually immunopositive for CK20 and carcinoembryonic antigen (CEA)

Supplementary Questions For each of the following, select the most likely diagnosis from the diagnostic set (an answer may be used once, more than once, or not at all).

Question Diagnostic Set

Which entity typically occurs in middle-aged women and is characterized by papillary fronds covered by stratified epithelial cells with scant cytoplasm, psammoma bodies and is WT1(+)?

A.  Choriocarcinoma
B.  Dysgerminoma
C.  Embryonal carcinoma
D.  Endometrioid carcinoma, secretory pattern
E. Serous tumor of borderline malignancy (low malignant potential)
F. Yolk sac tumor (endodermal sinus tumor)
2. Which entity may occur in combination with other ovarian germ cell tumors, exhibits a hemorrhagic cut surface, biphasic, and is cytokeratin(+) and hCG(+). A. Choriocarcinoma
B. Dysgerminoma
C. Embryonal carcinoma
D.  Endometrioid carcinoma, secretory pattern
E. Serous tumor of borderline malignancy (low malignant potential)
F. Yolk sac tumor (endodermal sinus tumor)
3. Which entity accounts for approximately 50% of malignant ovarian germ cell tumors arising in young women and is CD117(+), D2-40(+) and CD30(-)? A. Choriocarcinoma
B. Dysgerminoma
C. Embryonal carcinoma
D. Endometrioid carcinoma, secretory pattern
E. Serous tumor of borderline malignancy (low malignant potential)
F. Yolk sac tumor (endodermal sinus tumor)


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  2. Nogales FF, Bergeron C, Carlia RE, Alvaro T, Fulwood HR. Ovarian endometrioid tumors with yolk sac component. An unusual form of ovarian neoplasm: analysis of six cases. Am J Surg Pathol. 1996;20:1056-1066.
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