Reproducible diagnosis of ovarian carcinoma cell types is critical for cell type-specific treatment. The purpose of this study was to test the reproducibility of cell type diagnosis across Canada. Analysis of the interobserver reproducibility of histologic tumor type was performed among 6 pathologists after brief training in the use of modified World Health Organization criteria to classify ovarian carcinomas into 1 of 6 categories: high-grade serous, endometrioid, clear cell, mucinous, low-grade serous, and other. These 6 pathologists independently reviewed a test set of 40 ovarian carcinomas. A validation set of 88 consecutive ovarian carcinomas drawn from 5 centers was subject to local review by 1 of the 6 study pathologists, and central review by a single observer. Interobserver agreement was assessed through calculation of concordance and kappa values for pair-wise comparison. For the test set, the paired concordance between pathologists in cell type diagnosis ranged from 85.0% to 97.5% (average 92.3%), and the kappa values were 0.80 to 0.97 (average 0.89). Inclusion of immunostaining results did not significantly improve reproducibility (P=0.69). For the validation set, the concordance between original diagnosis and local review was 84% and between local review and central review was 94%. The kappa values were 0.73 and 0.89, respectively. With a brief training exercise and the use of defined criteria for ovarian carcinoma subtyping, there is excellent interobserver reproducibility in diagnosis of cell type. This has implications for clinical trials of subtype-specific ovarian carcinoma treatments.

Seventy-five malignant mesotheliomas of the peritoneum in women were reviewed to highlight their morphologic spectrum. The patients ranged from 17 to 92 (mean, 47.4) years of age. The clinical presentation was usually abdominal or pelvic pain, abdominal swelling (sometimes due to ascites), or a pelvic mass. On microscopic examination, the majority of the tumors had only an epithelial morphology, but 4 were biphasic and 1 was sarcomatoid. The most common epithelial patterns were tubular and papillary (which often coexisted), but 5 tumors were purely diffuse; 2 had cells with abundant glassy eosinophilic cytoplasm (so-called deciduoid mesothelioma). The cells in the tubular and papillary patterns were generally cuboidal with scant to moderate amounts of eosinophilic cytoplasm. Nuclear atypia was usually only mild, although a minority of cases had moderate or even, occasionally, severe atypia. Many tumors had foci that, viewed in isolation, resembled so-called well-differentiated papillary mesothelioma, and accordingly that diagnosis should be made cautiously. Unusual features were lymphoid follicles (13 cases), striking myxoid stroma (5 cases), prominent foamy histiocytes (5 cases), and a striking vascular proliferation (1 case). The varied morphology of peritoneal malignant mesotheliomas may raise a broad differential diagnosis, but in most cases the resemblance to other tumors is limited. Histochemistry, immunohistochemistry, and electron microscopy may provide important aid, particularly when tissue is limited, but should be needed only occasionally.

Endometrial stromal tumours (ESTs) are diagnosed in most instances by light microscopy. Often, the greatest challenge is to distinguish between the different subtypes of these tumours. Furthermore, a handful of new or relatively new entities have been described in the literature, which may cause problems in the differential diagnosis; highly cellular leiomyoma is the most common. In addition, new antibodies have been developed to help in the distinction of ESTs from their mimics, as there are prognostic and therapeutic implications. A practical approach is provided for the diagnosis of ESTs on the basis of systematic assessment of histological and immunohistochemical parameters, and recent developments related to these tumours are highlighted.

The use of frozen section in gynecological pathology has not been emphasized in the literature to the same degree as in other surgical fields. This review focuses on the indications, contraindications, and limitations of frozen-section diagnosis specific to the female genital tract. An intraoperative consultation in gynecological pathology is indicated (a) to ensure that the tissue sampled is adequate for diagnosis, (b) to determine the nature of a disease process, (c) to plan for appropriate ancillary studies, (d) to determine tumor spread, and (e) to assess the margins. In the ovary, mucinous tumors in particular may present a challenge and potential for misdiagnosis at the time of frozen section. It is important to determine the nature of the ovarian involvement, as tumor size greater than 10 cm or bilateral involvement strongly suggests a metastatic process. Also, the distinction between ovarian carcinoma and tumors of borderline malignancy may be difficult in a limited sampling. In the germ cell category, an important distinction is that of a dysgerminoma from a large cell lymphoma, due to different treatment regimes. Pregnant and postpartum women present a unique challenge as the effects of high levels of pregnancy-related hormones may result in lesions that closely mimic malignancy. Although intraoperative frozen section should be discouraged as a primary diagnostic procedure for endometrial carcinoma, it can be very helpful to identify those patients who are at risk for extrauterine spread and who may require lymphadenectomy. Analysis of a cone biopsy of the cervix by frozen section may be warranted particularly if the previous biopsy showed equivocal stromal invasion, an uncertain depth of invasion, there are issues related to fertility; however, the process is time consuming and may compromise the permanent sections if the lesion is very small. Frozen-section diagnosis in squamous cell carcinoma and in Paget disease of the vulva is infrequently requested as these entities are multifocal resulting in an inaccurate frozen-section diagnosis. Lastly, intraoperative evaluation of lymph nodes including the role of sentinel lymph nodes is discussed.