Low-grade serous carcinoma of the ovary displaying a macropapillary pattern of invasion

Distinct histopathological features are associated with molecular subtypes and outcome in low grade serous ovarian carcinoma

Low grade serous ovarian carcinoma (LGSOC) demonstrates unique clinical and molecular features compared to other ovarian cancer types. The relationship between common histological features of LGSOC and molecular events, such as hormone receptor expression patterns and MAPK gene mutation status, remains poorly understood. Recent data suggest some of these molecular features may be biomarkers of response to recently introduced biologically-targeted therapies, namely endocrine therapy and MEK inhibitors. We utilize a cohort of 63 pathologically-confirmed LGSOC cases with whole exome sequencing and hormone receptor expression data to investigate these relationships. LGSOC cases demonstrated uniformly high oestrogen receptor (ER) expression, but variable progesterone receptor (PR) expression intensity. 60% and 37% of cases demonstrated micropapillary and macropapillary patterns of stromal invasion, respectively. 63% of cases demonstrated desmoplasia, which was significantly associated with advanced disease stage and visible residual disease after cytoreductive surgery. MAPK-mutant cases (KRAS, BRAF, NRAS) more frequently demonstrated macropapillary stromal invasion, while Chr1p loss was associated with desmoplasia and low PR expression. Presence of micropapillary stromal invasion and low PR expression were associated with significantly poorer survival after accounting for stage and residual disease status. Together, these data identify novel relationships between histopathological features and molecularly-defined subgroups in LGSOC.

Novel Histologic Classification of Small Tumor Cell Nests for Lung Adenocarcinoma With Prognostic and Etiological Significance: Small Solid Nests and Pure Micropapillary Nests

Small tumor cell nests such as micropapillary nests are histologic poor prognostic markers for adenocarcinomas of various organs, including the lung. However, for the lung, the association of micropapillary patterns with smoking is controversial, which may be because of a vague definition of micropapillary patterns. This study clarifies the implications of small tumor cell nests by introducing a new dichotomic classification based on the glandular polarity of tumor cells: pure micropapillary nests (pMPs), preserving glandular polarity, and small solid nests (SSNs), lacking polarity. We examined the clinicopathologic factors in 436 resected adenocarcinomas, and analyzed the overall survival between groups classified by either the presence or absence of pMPs and SSNs. pMP was positively associated with nonsmoking-related features such as epidermal growth factor receptor mutations and thyroid transcription factor 1 expression. By contrast, SSN was positively associated with smoking-related features such as KRAS mutations and hepatocyte nuclear factor-4a expressions. Besides, pMP and SSN were significant and independent indicators of poor prognosis in all stages. SSN was an indicator in stage I too, whereas pMP was not. Furthermore, prognoses of the group with SSN were significantly worse than those of pMP-only group. In conclusion, the present study has revealed 2 completely different patterns of small tumor cell nests in lung adenocarcinoma, the nonsmoking-related pMPs, and the smoking-related SSNs, by considering glandular polarity. MPP should include only pMPs, and SSNs should be in a solid pattern. This novel classification might boast clinical significance as a potent poor prognostic marker as well as a factor reflecting etiological and genetic characters.

Clinicopathologic, Immunohistochemical, and Molecular Characteristics of Ovarian Serous Carcinoma With Mixed Morphologic Features of High-grade and Low-grade Serous Carcinoma

Despite the current classification of high-grade serous carcinoma (HGSCA) and low-grade serous carcinoma (LGSCA) as mutually exclusive diseases based on morphology and molecular pathogenesis, cases with mixed morphologic features of HGSCA and LGSCA have been reported. Herein we assess the clinicopathologic, immunohistochemical (IHC), and molecular genetic characteristics of a group of these cases, which we termed indeterminate grade serous carcinoma (IGSCA) in comparison with groups of HGSCA and LGSCA. Using the World Health Organization (WHO) classification criteria, we selected 27 LGSCA and 19 IGSCA for detailed morphologic study. Thirteen classic HGSCA, 19 classic LGSCA, and 19 IGSCA were selected for p53 and BRAF V600E IHC and molecular genetic testing by next-generation sequencing. IGSCA showed the architectural patterns of invasion of LGSCA, but with higher grade nuclear features focally and a mitotic index intermediate between LGSCA and HGSCA. Few cases in the IGSCA group showed mutant TP53 by IHC or sequencing (4/18, 22.2%), 1 case had mutant BRAF non-V600E by sequencing, and 1 had an NRAS mutation. When present, the mutations were identical in the low-grade and high-grade areas. The IGSCA group had a long-term survival similar to the classic HGSCA group. IGSCA with mixed morphologic features of HGSCA and LGSCA is a rare and potentially clinically aggressive variant of serous carcinoma. Their distinct morphologic, but heterogenous molecular features, including low frequency of TP53 and BRAF mutations suggest that these rare tumors may have a different pathogenesis pathway compared with classic HGSCA and classic LGSCA.

Ovarian tumors: a survey of selected advances of note during the life of this journal

The author reviews highlights of advances in knowledge concerning ovarian tumor pathology since the time of an essay in the first issue of this Journal written by Dr Robert E. Scully, who, both before and for several decades after the Journal was instituted, made many original contributions to the field and was the major architect of the 1973 World Health Organization classification of ovarian tumors which was much more clear and logical than prior ones. The current review considers the neoplasms in essentially the same order as was done in the first issue of this journal and presents a personal look at the highlights of new information concerning various well-known categories, surface epithelial, germ cell, sex cord-stromal, metastatic neoplasms and briefly, benign so-called tumor-like lesions. Some of the most notable developments are as follows: (1) an orderly approach to the classification of implants of serous borderline tumors into noninvasive and invasive categories; (2) recognition of distinctive micropapillary patterns seen in some borderline tumors and low-grade carcinomas; (3) a remarkable propensity for some endometrioid carcinomas to mimic sex cord- stromal tumors; (4) appreciation of the differences between primary mucinous tumors of intestinal and müllerian types; (5) the importance of distinguishing within primary mucinous carcinomas between expansile and destructive stromal invasion; (6) emphasis on the diagnosis of immature teratoma being based on the presence of primitive-embryonic-appearing tissues; (7) appreciation of variant morphology of cases of struma ovarii which may lead to significant diagnostic problems; (8) subdivision of granulosa cell tumors into adult and juvenile types because of the differing features of the two groups including in the second category the propensity for more malignant neoplasms to be mimicked; (9) recognition of a distinctive form of Sertoli-Leydig cell tumor, the retiform variant, with a propensity to occur in the young; (10) appreciation of a unique highly malignant neoplasm that typically afflicts the young and may be associated with hypercalcemia, so-called small cell carcinoma of hypercalcemic type; (11) greater awareness than was hitherto the case of the propensity for metastatic intestinal adenocarcinoma to mimic primary endometrioid carcinoma and similarly for metastatic mucinous carcinomas to simulate primary mucinous cystic tumors; (12) recognition of the distinctive features of low-grade appendiceal mucinous neoplasms that spread to the ovary and are typically associated with pseudomyxoma peritonei; and (13) appreciation that the histologic spectrum seen in cases of Krukenberg tumor is broader than often previously thought.

Architectural Histopathological Changes in Ovarian Serous Carcinomas

Ovarian serous carcinomas have a very large spectrum of growth patterns that contrast with the most primitive ovarian carcinomas, in which the morphology varies very much less. Serous carcinomas growth patterns include papillary and glandular aspects, but also cribriform, solid, microcystic and trabecular, some being common to the both high- and low-grade types of ovarian serous carcinomas, others being distinct. The study included 45 cases of ovarian serous carcinomas out of which five cases with low grade and 40 cases with high grade. High grade serous carcinomas were associated with mixed growth patterns, with large complex papillae, glands with irregular shape lined by stratified epithelia, often with areas of extended necrosis. In the case of low grade ovarian carcinomas we observed the association with more uniform growth patterns, micropapillary or glandular, the presence of optically empty slit-like spaces, psammoma bodies, the absence of necrosis and the association with a borderline or benign component. The recognition of the common histopathological aspects, allows a more accurate diagnosis of the ovarian serous carcinoma types and subtypes, which has a great importance in the actual era of personalized therapy.

BRAFV600E mutations and immunohistochemical expression of VE1 protein in low-grade serous neoplasms of the ovary

AIMS

The most common BRAF mutation in ovarian low-grade serous neoplasms (LGSNs) involves substitution of valine by glutamic acid at position 600 (V600E). Small studies have demonstrated high specificity of immunohistochemistry with mutation-specific monoclonal antibody VE1. We sought to investigate the expression of VE1 protein in LGSNs and its correlation with BRAF mutation-associated histological features and BRAF mutation status.

METHODS AND RESULTS

We reviewed pathology reports and available slides from ovarian serous borderline tumours (SBTs) and low-grade serous carcinomas (LGSCs) diagnosed between 2000 and 2012. VE1 immunohistochemistry was performed on formalin-fixed, paraffin-embedded tissue sections. Tumours with ≥50% positive cells were considered positive. Of 121 LGSNs, there were 73 SBTs, eight SBTs with micropapillary features (mpSBT) and 40 LGSCs (22 primary, 18 metastatic). VE1 was positive in 52% (38 of 73) of SBTs and 9% (two of 22) of primary LGSCs, and in none of the mpSBTs and metastatic LGSCs (P < 0.0001). Of 76 tumours with known mutation status, 42 (55%) harboured mutations, including BRAF^V600E (26, 34%), KRAS^G12D (eight, 11%), and KRAS^G12V (eight, 11%). BRAF^V600E mutations were present in 48% (25 of 52) of SBTs and 5% (one of 22) of LGSCs (P < 0.0001). VE1 was positive in 96% (25 of 26) of BRAF^V600E -mutated tumours and correlated with BRAF mutation-associated histological features (P < 0.0001).

CONCLUSIONS

BRAF^V600E mutations are significantly more common in SBTs than in LGSCs. Immunohistochemical expression of VE1 protein is associated strongly with BRAF^V600E mutation and BRAF mutation-associated histological features. VE1 immunohistochemistry is a reliable method for the detection of BRAF^V600E mutations.

Ovarian Cancer in Hereditary Cancer Susceptibility Syndromes

Hereditary breast and ovarian cancer (HBOC) syndrome and Lynch syndrome (LS) are associated with increased risk of developing ovarian carcinoma. Patients with HBOC have a lifetime risk of up to 50% of developing high-grade serous carcinoma of tube or ovary; patients with LS have a 10% lifetime risk of developing endometrioid or clear cell carcinoma of the ovary. Testing all patients with tubo-ovarian high-grade serous carcinoma for mutations associated with HBOC syndrome, and all patients presenting with endometrioid or clear cell carcinoma of the ovary for mutations associated with LS can identify patients with undiagnosed underlying hereditary cancer susceptibility syndromes.

Is Invasive Micropapillary Serous Carcinoma a Low-grade Carcinoma?

"Invasive micropapillary serous carcinoma" has been proposed as a synonym for low-grade serous carcinoma by some expert pathologists. In contrast, Singer and colleagues reported that some serous carcinomas with conspicuous invasive micropapillary pattern (SC-IMPs) can show high-grade nuclear atypia. However, the molecular features of such tumors have not been well documented. The aim of this study was to demonstrate and emphasize the fact that high-grade serous carcinoma confirmed by immunohistochemistry and molecular analysis can show conspicuous invasive micropapillary pattern. We selected 24 "SC-IMPs" and investigated: (1) their morphologic features; (2) the immunostaining pattern of p53 protein; and (3) KRAS/BRAF/TP53 gene mutations. The 24 SC-IMPs were subdivided into low-grade and high-grade tumors based primarily on the nuclear atypia, with the mitotic rate used as a secondary feature: low grade (n=5) and high grade (n=19). Low-grade SC-IMPs were characterized by low-mitotic activity, absence of abnormal mitosis, presence of serous borderline tumor, occasional BRAF mutation, and infrequent TP53 mutation. High-grade SC-IMPs were characterized by high-mitotic activity, presence of abnormal mitosis, conventional high-grade serous carcinoma, frequent TP53 mutation, and lack of KRAS/BRAF mutation. We demonstrated that high-grade serous carcinoma confirmed by aberrant p53 immunostaining and molecular analysis can show conspicuous invasive micropapillary pattern, validating Singer and colleague's report. Serous carcinoma with conspicuous invasive micropapillary pattern should not be readily regarded as low-grade serous carcinoma. Nuclear grade is the most important diagnostic feature in the SC-IMPs.

[Update on gynecopathology]

Recent years have witnessed significant achievements in light microscopic, immunohistochemical and molecular diagnostics in gynecopathology. In this article four topics will be discussed as examples. The squamous precancerous and carcinomatous lesions of the female anogenital tract and the cervix are caused by a transforming high risk human papillomavirus (HPV) infection. No differences in morphological findings can be found between the different locations. In contrast to the current WHO classification a new categorization into low grade and high grade precancerous lesions is suggested. Only some cervical adenocarcinomas are related to high risk HPV infection. Nevertheless, some of these unusual variants demonstrate p16 overexpression. Uterine leiomyosarcomas are clinically aggressive neoplasms independent of the histological grade and in most cases curative treatment is not feasible. It is most important to distinguish leiomyosarcoma from those leiomyoma variants which mimic uterine leiomyosarcoma. Pelvic and ovarian serous carcinomas can be separated into low grade and high grade types which differ significantly in formal pathogenesis, molecular features and pathomorphological findings. Significant differences are also obvious in clinical behavior and response to chemotherapy regimens.

Advanced stage micropapillary serous borderline ovarian tumor in a postmenopausal woman: a case report

Serous borderline ovarian tumors (SBOT) generally occur in young women, present at early stages and are associated with an excellent prognosis. However, there are rare subtypes of SBOT which may exhibit a more aggressive course. In contrast with other types of SBOT, the micropapillary variant SBOT (SBOT-MP) tends to present at advanced stages. Herein, we present a rare case of a SBOT-MP that occurred in a 66-year-old woman, who had tumoral involvement on bilateral ovaries, sigmoid serosa and a positive peritoneal cytology. The currently recommended treatment options for these cases are also discussed.

Ovarian low-grade and high-grade serous carcinoma: pathogenesis, clinicopathologic and molecular biologic features, and diagnostic problems

Ovarian serous carcinomas have been graded using various systems. Recently, a 2-tier system in which tumors are subdivided into low grade and high grade has been proposed. This approach is simplistic, reproducible, and based on biologic evidence indicating that both tumors develop via different pathways. Low-grade serous carcinomas exhibit low-grade nuclei with infrequent mitotic figures. They evolve from adenofibromas or borderline tumors, have frequent mutations of the KRAS, BRAF, or ERBB2 genes, and lack TP53 mutations (Type I pathway). The progression to invasive carcinoma is a slow step-wise process. Low-grade tumors are indolent and have better outcome than high-grade tumors. In contrast, high-grade serous carcinomas have high-grade nuclei and numerous mitotic figures. Identification of a precursor lesion in the ovary has been elusive and therefore the origin of ovarian carcinoma has been described as de novo. More recently, studies have suggested that a proportion seem to originate from intraepithelial carcinoma in the fallopian tube. The development of these tumors is rapid (Type II pathway). Most are characterized by TP53 mutations and lack mutations of KRAS, BRAF, or ERBB2. Although both types of serous carcinomas evolve along different pathways, rare high-grade serous carcinomas seem to arise through the Type I pathway. Immunohistochemical stains for p53, p16, and Ki-67 for distinction of low-grade from high-grade tumors are of limited value but can be helpful in selected instances. This review provides an update on the pathogenesis and clinicopathologic features of these 2 types of serous carcinomas and addresses some of the diagnostic problems that are encountered in routine practice.