Endometrial tumors with yolk sac tumor-like morphologic patterns or immunophenotypes: an expanded appraisal

Controversies in malignant ovarian germ cell tumors

Malignant ovarian germ cell tumors (MOGCT) are rare and often aggressive cancers that predominantly affect young women. Fortunately, combined surgery and chemotherapy results in high cure rates. In this review, we will consider some of the many controversies and poorly understood areas in the management of MOGCT that have arisen largely because of the lack of randomized trial data. This paucity of strong evidence is unsurprising, given the rarity of MOGCT and their multiple subtypes which differ biologically and in their clinical behavior. We will explore what is known about the biology and prognostic factors, and how the disease differs from its much more common and robust evidence-based male testicular counterpart. The type and extent of surgery, the value of surveillance in early-stage disease, and the role of neoadjuvant chemotherapy in advanced cases remain uncertain. In addition, optimizing outcomes in relapsed disease following initial chemotherapy is a key area for future development, as survival in this situation is worse than that in patients with testicular germ cell tumors. Fertility preservation remains of central importance, but the best way to achieve it remains debated. Finally, the type and duration of surveillance after treatment remain unclear. These and other controversies are discussed below.

Beyond the WHO 2020 Classification of Female Genital Tumors: Types of Endometrial Cancer: A Pathological and Molecular Focus on Challenging Rare Variants

Endometrial carcinoma is a heterogeneous group of malignancies characterized by distinct histopathological features and genetic underpinnings. The 2020 WHO classification has provided a comprehensive framework for the categorization of endometrial carcinoma. However, it has not fully addressed the spectrum of uncommon entities that are currently not recognized by the 2020 WHO and have only been described in the form of small case series and case reports. These neoplasms represent a real diagnostic challenge for pathologists; furthermore, their therapeutic management still remains controversial and information regarding tumor prognosis is very limited. This review aims to elucidate these lesser-known variants of endometrial carcinoma. We discuss the challenges of identifying these rare subtypes and the molecular alterations associated with them. Furthermore, we propose the need for expanded classification systems that include these variants to enhance clinical outcomes and research efforts. We believe that a better histological typing characterization of these entities may lead to more reproducible and accurate diagnoses and more personalized treatments. By raising awareness of these rare entities, we also hope to encourage further investigation and integration into clinical practice to improve patient care in endometrial carcinoma.

Yolk Sac Differentiation in Endometrial Carcinoma: Incidence and Clinicopathologic Features of Somatically Derived Yolk Sac Tumors Versus Carcinomas With Nonspecific Immunoexpression of Yolk Sac Markers

Endometrial somatically derived yolk sac tumors are characterized by yolk sac morphology with AFP, SALL-4, and/or Glypican-3 immunoexpression. Yolk sac marker expression, however, is not limited to tumors with overt yolk sac histology. Three hundred consecutive endometrial malignancies were assessed for immunomarkers of yolk sac differentiation. Of these, 9% expressed ≥1 yolk sac marker, including 29% of high-grade tumors. Only 3 (1%) met morphologic criteria for yolk sac differentiation; these were originally diagnosed as serous, high-grade NOS, and dedifferentiated carcinoma. Two were MMR-intact and comprised exclusively of yolk sac elements, while the dedifferentiated case was MMR deficient and had a background low-grade endometrioid carcinoma; this case also showed BRG1 loss. All 3 were INI1 intact. Nonspecific yolk sac marker expression was seen in 14 carcinosarcomas, 4 endometrioid, 2 serous, 1 clear cell, 1 dedifferentiated, 1 mixed serous/clear cell, and 1 mesonephric-like carcinoma. INI1 was intact in all cases; one showed BRG1 loss. Twenty were MMR-intact, and 4 were MMR deficient. All MMR-deficient cases with yolk sac marker expression, both with and without true yolk sac morphology, had no evidence of residual disease on follow-up, whereas 82% of MMR-intact cases developed recurrent/metastatic disease. In summary, endometrial somatically derived yolk sac tumors were rare but under-recognized. While AFP immunostaining was specific for this diagnosis, Glypican-3 and SALL-4 expression was seen in a variety of other high-grade carcinomas. INI1 loss was not associated with yolk sac morphology or immunomarker expression in the endometrium, and BRG1 loss was rare. All patients with MMR-deficient carcinomas with yolk sac immunoexpression +/- morphology were disease-free on follow-up, whereas the majority of MMR-intact cancers showed aggressive disease.

GATA3 immunohistochemistry as a diagnostic adjunct for differentiated vulvar intraepithelial neoplasia: utility and limitations

Herein, the authors evaluate the diagnostic utility and limitations of GATA3 immunohistochemistry for the distinction of differentiated vulvar intraepithelial neoplasia (dVIN) from its potential mimics. Immunohistochemical studies for GATA3, p53, and p16 were performed on 124 pathologic vulvar tissues, inclusive of dVIN (n = 21), vulvar aberrant maturation (n = 10), high-grade squamous intraepithelial lesion (HSIL) (n = 44), and 49 non-neoplastic vulvar dermatoses of various types. GATA3 expression was scored using a modification of previously proposed criteria: pattern 0 (no significant loss of basal layer staining, >75% staining), pattern 1 (25-75% staining), and pattern 2 (<25% staining). With the exception of lichen sclerosus, 8% of which showed pattern 1 or 2 staining, all other non-neoplastic lesions showed pattern 0 expression. Aberrant GATA3 expression (i.e., patterns 1 or 2) was present in 90% of dVIN cases (2 [9.5%], 3 [14.3%], 16 [76.2%] with patterns 0, 1, and 2 respectively), 90% of vulvar aberrant maturation cases (1 [10%],7 [70%], 2 [20%] with patterns 0, 1, and 2 respectively), and 15.9% of HSIL cases (84.1% pattern 0; 2.3% pattern 1; 13.6% pattern 2). All HSIL cases were p16 positive, including the 7 pattern 1 and 2 cases. All cases of dVIN-like HSIL were pattern 0, and all (n = 2) cases of HSIL-like (basaloid) dVIN were pattern 2 (both of the latter cases displayed complete absence of epidermal staining). Only 1 dVIN case was both pattern 0 and p53-wild-type. We conclude that GATA3 is useful for the distinction of dVIN from non-neoplastic dermatoses and from HSIL, but is best used as part of a panel that includes p53 and p16 to mitigate its limitations.

Evaluation of Lineage/Site-specific Nuclear Immunohistochemical Markers SATB2, Cyclin D1, SALL4, and BCOR in High-grade Endometrial Carcinomas

Poorly differentiated malignant neoplasms involving the gynecologic tract routinely include a poorly differentiated endometrial carcinoma (EC) in the differential diagnosis. Some nuclear lineage/site-specific immunohistochemical markers are utilized in this diagnostic setting including SATB2, cyclin D1, SALL4, and BCOR, but their specificity and use in small samples are not clear across the spectrum of ECs. Cases of undifferentiated/dedifferentiated endometrial carcinomas (UEC/DDEC), clear cell carcinoma (CCC), uterine serous carcinoma (USC), FIGO grade 3 endometrial endometrioid carcinoma (EEC), and uterine carcinosarcoma (UCS) were identified and diagnoses confirmed. Whole-section immunohistochemical stains for SATB2, cyclin D1, SALL4, BCOR, and PAX8 were performed. A total of 113 cases were utilized: 15 CCC, 26 EEC, 19 UCS, 22 USC, and 31 UEC/DDEC. Cases were distributed across both low (49%) and high (51%) FIGO clinical stages. SATB2 was expressed by UCS (8/19, 42%), EEC (10/26, 38%), UEC/DDEC (11/30, 37%), and USC (6/22, 27%). Cyclin D1 was expressed by EEC (24/26, 92%), USC (17/22, 77%), UEC/DDEC (15/20 EEC component, 75%; 22/30 UEC, 73%), UCS (10/16 carcinoma, 63%; 11/19 sarcoma, 58%), and CCC (8/15, 53%). SALL4 was expressed most frequently by UEC/DDEC (12/30, 40%), but also USC (7/22, 32%), EEC (5/26, 19%), and UCS (4/16 carcinoma, 25%; 3/19 sarcoma, 16%). BCOR was expressed at low levels in 2 USC, 2 UEC/DDEC, and 2 UCS. PAX8 was generally positive but showed lower expression in UEC/DDEC (17/30, 57%) and in the sarcomatous portions of UCS (6/19, 32%). SATB2, cyclin D1, SALL4, and BCOR stain variable numbers of poorly-differentiated EC and must be carefully interpreted within morphologic and clinical context.

Cracking the case: The diagnosis and treatment of a complex high-grade endometrial carcinoma with hepatoid, endometrioid, serous features and somatically derived yolk sac tumor component in a 50 year old female

•Alpha-fetoprotein secreting tumors in gynecologic cancers have a broad differential.•Surgical pathology may provide a more comprehensive picture of tumor heterogeneity than initial biopsy.•Yolk Sac Tumor components intermixed with carcinoma points towards a somatic derivative rather than a collision tumor.•Alpha-fetoprotein can be trended over time to gauge response to treatment of cancers that produce the protein.

Ovarian Mucinous Carcinoma with a Yolk sac Tumor-Like Component: A Report of Three Cases with a Literature Review for Prognostic Analysis

The most common subtype of ovarian carcinoma associated with somatically derived yolk sac tumor (YST) is endometrioid carcinoma. Only two cases of ovarian mucinous carcinomas associated with YST have been reported; herein, we present three additional patients, along with a review of previous literature and our pathology archives to analyze the tumor prognosis. The patients' ages ranged from 38 to 53 years. Two patients had FIGO stage 1 tumors, and one patient had a stage 3 tumor. Two patients died of the disease within a year, and one patient survived with distant metastasis (32 months after surgery). In all three tumors, the YST-like component comprised less than 5% of the total tumor area. Together with the two previously reported mucinous carcinomas with a YST-like component, the prognosis of the five mucinous carcinomas with a YST-like component were compared with that of 19 conventional mucinous carcinomas resected at our hospital. The survival curves were estimated using the Kaplan-Meier method. As a result, the overall survival rate of patients with mucinous carcinomas with a YST-like component was significantly lower than that of patients with conventional mucinous carcinomas (P = .0014). Our study indicates that the presence of a YST-like component in mucinous carcinomas would be a strong prognostic indicator.

Mucinous Proliferations of the Uterine Corpus: Comprehensive Appraisal of an Evolving Spectrum of Neoplasms

A variety of endometrial lesions may contain mucinous cells. Herein, the author reviews the literature on the classification and clinicopathologic significance of uterine corpus proliferations with a significant mucinous component, assesses the 2020 World Health Organization classification of such lesions, and presents a diagnostic framework. The key epithelial mucinous lesions include mucinous metaplasia, atypical mucinous glandular proliferation and mucinous carcinoma. Each of these categories are classifiable into "usual" and gastrointestinal subtypes, the latter being indicative of intestinal (presence of goblet cells) and/or gastric-type (abundant, pale eosinophilic or clear cytoplasm and well-defined cell borders) morphology. It has been proposed that at least focal expression of gastrointestinal immunohistochemical markers be required for all gastrointestinal type lesions, and for gastrointestinal type atypical mucinous glandular proliferation and carcinoma, minimality or absence of estrogen receptor expression, and the absence of an endometrioid component. Mucinous carcinomas of the usual type, in which >50% of the tumor is comprised of a mucinous component, are the most common. Morphologic subtypes include mucinous carcinoma with microglandular features and mucinous carcinoma with signet rings (signet ring carcinoma). Endometrioid carcinomas with a less than a 50% mucinous component are classified as endometrioid carcinoma with mucinous differentiation. Several studies have directly compared endometrioid and mucinous carcinomas, the latter presumably of the usual type, with respect to patient outcomes after treatment. All have found no difference in overall and disease free survival between these groups. However, three major studies have found mucinous carcinomas to be associated with a higher risk of lymph node metastases. Nineteen cases of mucinous carcinoma of the gastrointestinal type have been reported, and the limited data on their follow-up after primary treatment suggests that this subtype is more clinically aggressive and should accordingly be classified separately from mucinous carcinomas of the usual type. The morphologic spectrum of mucinous carcinoma of the gastrointestinal type is unclear and continues to evolve. Mucinous change, which may sometimes be extensive, may also be associated with papillary proliferation of the endometrium, adenomyoma of the endocervical type, atypical, and typical adenomyomas. In a curettage or biopsy, intestinal type mucinous epithelium may be indicative of any of the gastrointestinal lesions mentioned above, but may also represent samplings of uterine teratomas, yolk sac tumors, genital and extragenital adenocarcinomas with intestinal differentiation, or low-grade appendiceal mucinous neoplasms that secondarily involve the endometrium.

α-Fetoprotein-Producing Endometrial Carcinoma Is Associated With Fetal Gut-Like and/or Hepatoid Morphology, Lymphovascular Infiltration, TP53 Abnormalities, and Poor Prognosis: Five Cases and Literature Review

The clinicopathological, immunohistochemical, and molecular characteristics of α-fetoprotein (AFP)-producing endometrial carcinoma (AFP+ EC) are poorly understood. From 284 cases of endometrial carcinoma in our pathology archive, we identified five cases (1.8%) of AFP+ EC with fetal gut–like (4/5) and/or hepatoid (2/5) morphology. All cases exhibited lymphovascular infiltration. In addition, 24 cases of endometrial carcinoma with elevated serum AFP levels were retrieved from the literature. The patient age ranged from 44 to 86 years (median: 63). Of 26 cases whose FIGO (International Federation of Gynecology and Obstetrics) stage and follow-up information was available (mean follow-up 24 months), 15 were stage I or II and 11 were stage III or IV. Even in stage I or II disease, death or relapse occurred in more than half of the patients (8/15). Detailed analysis of our five cases revealed that, on immunohistochemistry, AFP+ EC was positive for SALL4 (4/5), AFP (3/5), and HNF1β (4/5) in >50% of neoplastic cells and negative for estrogen and progesterone receptors (5/5), PAX8 (4/5), and napsin A (5/5). Four cases exhibited aberrant p53 immunohistochemistry and were confirmed to harbor TP53 mutations by direct sequencing. No mutation was found in POLE, CTNNB1, or KRAS. In conclusion, AFP+ EC merits recognition as a distinct subtype of endometrial carcinoma, which occurs in 1.8% of endometrial carcinoma cases, are associated with TP53 abnormalities, exhibit lymphovascular infiltration, and can show distant metastasis even when treated in early stage.

Yolk Sac Tumor Arising in Uterine Carcinosarcoma With Endometrioid and Serous Components: A Case Report With Immunohistochemical Analysis

Yolk sac tumor of the endometrium is an uncommon neoplasm. Here we report a case of yolk sac tumor arising in a uterine carcinosarcoma, with the carcinomatous component showing both endometrioid and serous components, and the sarcomatous component showing homologous (spindled) differentiation. The yolk sac tumor showed predominant glandular configuration and was present admixed with the epithelial components. Extensive immunostaining was performed to narrow the differential diagnosis, including potentially therapeutic testing for HER-2. To our knowledge, this is the first case of carcinosarcoma with this mix of epithelial components and corresponding reporting of these immune and therapeutic markers.

Combination IETA Ultrasonographic Characteristics Simple Scoring Method With Tumor Biomarkers Effectively Improves the Differentiation Ability of Benign and Malignant Lesions in Endometrium and Uterine Cavity

Objectives

To evaluate International Endometrial Tumor Analysis (IETA) ultrasonographic characteristics simple scoring method and tumor biomarkers for the diagnosis of uterine cavity and endometrial lesions.

Methods

We classified and scored the normalized description of IETA ultrasonic characteristics, according to IETA expert consensus literature, previous IETA-related research articles, and the previous research experience of this project group. We conducted a retrospective analysis of the ultrasound images of 594 patients enrolled from January 2017 to June 2020, scored them item by item, and finally calculated the total score of each case. Meanwhile, we combined the results of seven tumor biomarkers. The objective was to evaluate the sensitivity, specificity, coincidence rate, and the area under receiver operating characteristic (ROC) curve of IETA ultrasonographic characteristics simple scoring method and tumor biomarkers for benign and malignant uterine cavity or endometrial lesions. The diagnostic efficiency between the combined method and the single method was compared.

Results

A total of 594 cases were confirmed by postoperative pathology or surgery records, including 475 benign lesions and 119 malignant lesions. In the simple ultrasound scoring method, the average score of benign lesions was 3.879 ± 1.279 and that of malignant lesions was 9.676 ± 4.491. If ≥6.5 points was taken as the cutoff value for the judgment of malignant lesions, the sensitivity, specificity, coincidence rate, and the area under receiver operating characteristic (ROC) curve (AUC) were 76.5%, 96.0%, 92.1%, and 0.935, respectively. The difference in tumor antigen 19-9 (CA19-9) and human epididymal protein 4 (HE4) between benign and malignant lesions was statistically significant (all p ≤ 0.01). The other five tumor biomarkers (CA125, CA15-3, SCC-Ag, AFP, and CEA) showed no statistically significant difference in benign and malignant lesions. If the value of CA19-9 ≥13.96 U/ml was taken as cutoff value, the sensitivity, specificity, and coincidence rate of the diagnosis of endometrial benign and malignant lesions were 54.8%, 74.7%, and 70.7%, respectively, and the AUC was 0.620. If the value of HE4 ≥ 39.075 pmol/L was taken as cutoff point, the sensitivity, specificity, coincidence rate, and AUC were 77.4%, 67.9%, 69.8%, and 0.796, respectively. The sensitivity was increased to 97.6% and the AUC was 0.939 when IETA ultrasound characteristics simple scoring method combined CA19-9 and HE4 in parallel test.

Conclusions

In IETA ultrasound characteristics simple scoring method, with ≥6.5 points as the cutoff value, it could quickly and accurately assess the benign and malignant in uterine cavity and endometrial lesions, with high diagnostic value. The diagnostic efficacy of seven tumor biomarkers was all mediocre. Combining with these two methods, the comprehensive diagnosis could improve sensitivity and accuracy and reduce the risk of missed diagnosis.

Pattern of placental alkaline phosphatase (PLAP) expression in human tumors: a tissue microarray study on 12,381 tumors

Placental alkaline phosphatase (PLAP) is commonly expressed at high levels in testicular germ cell tumors. PLAP immunohistochemistry (IHC) is thus often used to confirm this diagnosis, especially in cases of putative metastasis. However, other tumors can also express PLAP. To comprehensively determine PLAP expression in normal and tumor tissue, a tissue microarray containing 16,166 samples from 131 different tumor types and subtypes as well as 608 samples from 76 different normal tissue types was analyzed by IHC. Moderate to strong PLAP positivity was found in 27 (21%) of 131 different tumor types including seminoma (96%), embryonal carcinoma (85%), and yolk sac tumors of the testis (56%); endometrioid carcinoma of the endometrium (28%) and the ovary (20%); gastric adenocarcinoma (22%); serous carcinoma (not otherwise specified) of the ovary (17%) and the uterus (11%); adenocarcinoma of the ampulla of Vater (15%); carcinosarcoma of the ovary (11%) and the uterus (8%); esophageal adenocarcinoma (10%); invasive urothelial carcinoma (4%); cholangiocarcinoma (2%); and adenocarcinoma of the lung (1%). Low‐level PLAP immunostaining, often involving only a small fraction of tumor cells, was seen in 21 additional tumor entities. The clinical significance of PLAP expression may vary between tumor types as high PLAP expression was linked to advanced pathological tumor stage (p = 0.0086), nodal metastasis (p = 0.0085), and lymphatic (p = 0.0007) and blood vessel invasion (p = 0.0222) in colorectal cancer, but to low pathological tumor stage in endometrial cancer (p = 0.0043). In conclusion, our data identify several tumor entities that can show PLAP expression at comparable levels to testicular germ cell tumors. These tumor entities need to be considered in cases of PLAP‐positive metastasis. Low‐level PLAP expression can be found in various other tumor entities and should generally not be viewed as a strong argument for germ cell neoplasia.

Extrauterine Mesonephric-like Neoplasms: Expanding the Morphologic Spectrum

Mesonephric-like adenocarcinomas (MLA) are rare neoplasms arising in the uterine corpus and ovary which have been added to the recent 2020 World Health Organization Classification of Female Genital Tumors. They have similar morphology and immunophenotype and exhibit molecular aberrations similar to cervical mesonephric adenocarcinomas. It is debated as to whether they are of mesonephric or Mullerian origin. We describe the clinical, pathologic, immunohistochemical, and molecular features of 5 cases of extrauterine mesonephric-like proliferations (4 ovary, 1 extraovarian), all with novel and hitherto unreported features. These include an origin of MLA in extraovarian endometriosis, an association of ovarian MLA with high-grade serous carcinoma, mixed germ cell tumor and mature teratoma, and a borderline ovarian endometrioid tumor exhibiting mesonephric differentiation. Four of the cases exhibited a KRAS variant and 3 also a PIK3CA variant. In reporting these cases, we expand on the published tumor types associated with MLA and report for the first time a borderline tumor exhibiting mesonephric differentiation. We show the value of molecular testing in helping to confirm a mesonephric-like lesion and in determining the relationship between the different neoplastic components. We provide further evidence for a Mullerian origin, rather than a true mesonephric origin, in some of these cases. We also speculate that in the 2 cases associated with germ cell neoplasms, the MLA arose out of the germ cell tumor.

Molecular characterization of uterine and ovarian tumors with mixed epithelial and germ cell features confirms frequent somatic derivation

Ovarian germ cell tumors, including yolk sac tumors, are most commonly diagnosed in children and young women. Most so-called yolk sac tumors reported in women >35 years old have been associated with an epithelial proliferation (endometriosis or carcinoma). Here, we describe eight cases clinically diagnosed as uterine or ovarian germ cell tumors in women >35 years old. In addition to routine morphologic examination and immunohistochemical evaluation, we present data from targeted next-generation sequencing (NGS) and isochromosome (12p) fluorescence in situ hybridization (FISH). We identified two groups of tumors with mixed germ cell and epithelial features: (1) tumors with background endometriosis and endometrioid carcinoma-like mutations (PTEN, PIK3CA, FGFR2, and CTNNB1), and (2) high-grade morphology, presumptive presence of isochromosome (12p) by FISH, and TP53 or PIK3CA mutations. These findings support the notion that the "germ cell tumor" component of these tumors is often somatically derived. Two tumors in our cohort were from premenopausal women; one showed no detectable mutations by NGS (suggestive of germ cell derivation), whereas the other showed PIK3CA, PTEN, and CTNNB1 mutations (suggestive of somatic derivation). Accurate classification of these tumors is likely important for selection of appropriate chemotherapy.

Malignant tumours of the uterus and ovaries with Mullerian and germ cell or trophoblastic components have a somatic origin and are characterised by genomic instability. Histopathology 2020;77:788-797. [PMID: 32558949 DOI: 10.1111/his.14188]

AIMS

Tumours of the female genital tract with a combination of malignant Mullerian and germ cell or trophoblastic tumour (MMGC/T) components are usually diagnosed in postmenopausal women, and pursue an aggressive clinical course characterised by poor response to therapy and early relapses. These clinical features suggest that MMGC/T are somatic in origin, but objective molecular data to support this interpretation are lacking. This study evaluates the molecular features of nine MMGC/T, including seven tumours containing yolk sac tumour (YST), one tumour containing choriocarcinoma and one tumour containing epithelioid trophoblastic tumour. The objectives were to: (i) investigate whether MMGC/T show a distinct genetic profile and (ii) explore the relationship between the different histological components.

METHODS AND RESULTS

Next-generation sequencing of paired samples demonstrated that the mutational profile of the Mullerian and non-Mullerian components of the tumour were almost identical in all cases. Moreover, the driver mutations identified were those expected in the specific subtype of Mullerian component present in each case. In contrast, variants expected in postpubertal germ cell tumours and gestational trophoblastic tumours were not identified, and FISH for i(12p) was negative in all cases tested. In this study, mismatch repair-proficient MMGC/T (eight of nine) were characterised by a complex copy-number variant profile, including numerous focal, regional, arm-level and chromosome-level events.

CONCLUSIONS

Comparison of paired samples supports that the YST and trophoblastic tumour components of MMGC/T have a somatic origin and often show numerous copy-number variants, suggestive of underlying genomic instability.

Pediatric vulvar malignancies: rare but important to know

Malignancies of the vulva in the pediatric population are exceptionally rare, which makes it difficult to gain any insight into their clinicopathologic profile. In this review, we summarize all published cases of a vulva malignancy in pediatric patients (≤21 years) reported in the English language literature for the 50-year period between 1970 and 2020. We estimate that less than 100 malignancies have been reported in total, approximately 50% of which were rhabdomyosarcomas. Invasive squamous cell carcinomas, yolk sac tumors, Ewing sarcoma/primitive neuroectodermal tumors (ES/PNET) and melanomas each represented approximately 10% of reported cases. For rhabdomyosarcoma, the alveolar and embryonal subtypes were reported with equal frequency, with both representing 70% of cases combined. The average patient age was 9.8 years. 48% and 35% were Intergroup Rhabdomyosarcoma Study clinical groupings I and III respectively. Managements were generally multimodal, and overall outcomes for the group were favorable. For invasive squamous cell carcinoma, the patients were all in their teenage years, with an average age at diagnosis of 15.2 years. A small subset of cases were associated with human papillomavirus and immunosuppression, and it is possible that immunosuppression has a role in vulvar squamous carcinogenesis in this population. One case was associated with lichen sclerosus. The patients with yolk sac tumors ranged in age from less than 1 year to 20 years (mean 12) and 67% of cases were stage I at presentation. An insufficient number of cases have been reported to define their prognosis, although some cases were notably aggressive. The few reported cases of melanoma are distinctive only because they were all associated with lichen sclerosus, suggestive of some role for the latter in their pathogenesis. The average age of patients reported with ES/PNET was 15 years (range 3.3 to 20). At least half of the reported cases were advanced stage at presentation, and patient outcomes were notably poor: 62.5% were dead of disease at follow-up. Pediatric vulvar malignancies are rare and are mostly comprised of 5 entities. Their accurate pathologic classification is necessary to facilitate optimal management.