Amplification of MDM2 and Loss of p16 Expression: Do They Have a Role in Malignant Transformation of Ovarian Brenner Tumor?

Immunohistochemistry as an adjunct for challenging histological patterns of borderline Brenner tumors: An illustrative study of 4 cases

Borderline Brenner tumors (BBT) have a range of morphology that shows considerable overlap with that of malignant Brenner tumors (MBT). In particular, two histological patterns of BBT can be particularly challenging: 1) BBT with intraepithelial carcinoma (BBT-IEC) and 2) BBT with a small nested pattern (BBT-SNP). BBT-IEC is characterized by a tumor with the low-power non-infiltrative silhouette of a conventional BBT, but with increased cytological atypia and mitotic activity similar to that of MBT. Conversely, BBT-SNP is characterized by a complex proliferation of small tumor nests that closely resemble the infiltrative growth pattern of MBT, but without the obligate cytologic atypia and mitotic activity of MBT. We suggest that the combination of p16, p53 and Ki-67 may be helpful in distinguishing these 2 patterns of BBT from both conventional BBT and from MBT. While both conventional BBT and BBT-IEC show a null pattern of p16 expression, our case of BBT-IEC showed aberrant p53 overexpression, albeit with a maturation pattern similar to that described for TP53 mutant mucinous ovarian carcinoma and differentiated vulvar intraepithelial neoplasia (dVIN). Similarly, while BBT-SNP shows an infiltrative-like growth pattern similar to that of MBT, our case also showed a wild-type pattern of p53 expression and a Ki-67 proliferative index similar to areas with conventional BBT histology. In conclusion, in our small case series, we show that the use of immunohistochemistry for p53 and Ki-67 may help to distinguish challenging patterns of BBT from MBT. Further studies are needed to validate this finding in a larger case cohort.

Coexistence of malignant ovarian Brenner tumor and borderline mucinous cystadenoma, combined with primary uterine corpus endometrioid carcinoma: A case report and literature review

Malignant Brenner tumor (MBT) of the ovary is a rare malignant ovarian tumor, whereas uterine corpus endometrioid carcinoma (UEC) constitutes one of the most common malignant tumors of the female reproductive system. The present study reported on a case of the coexistence of ovarian MBT and borderline mucinous cystadenoma combined with primary UEC. Therefore, the present case is a synchronous primary cancer of both ovary and endometrium. Although synchronous primary cancers of the endometrium and ovary are relatively uncommon, they are not rare; however, due to the rarity of MBT, this case was considered singular. To the best of our knowledge, this was the first-ever reported case of the coexistence of an ovarian MBT and borderline mucinous cystadenoma combined with primary UEC. Based on a review of the literature associated with the present case, its clinicopathological features, immunohistochemical phenotype, differential diagnosis, molecular changes, prognosis and treatment were summarized and discussed. The aim of the present study was to improve the understanding of this rare synchronous primary cancer of the ovary and endometrium so as to avoid future misdiagnosis.

MDM2 amplification in malignant Brenner tumors may play a role in progression to malignancy and aid in separation from urothelial and other ovarian carcinomas

Malignant Brenner tumor (MBT) is diagnosed in the setting of invasive high-grade carcinoma with urothelial-like morphology and the presence of an adjacent benign Brenner tumor (BBT) or borderline Brenner tumor (BLBT). MDM2 amplification was recently detected by next-generation sequencing on a small number of MBTs, potentially significant for future targeted therapy. Experience is limited, however, and evaluation of widely available MDM2 immunohistochemistry (IHC) has not been performed to determine clinical utility. After confirming all diagnoses morphologically and immunohistochemically, we performed MDM2 IHC on 4 MBTs, 3 BLBTs, 26 BBTs, 142 high-grade serous carcinomas (HGSC), 6 ovarian endometrioid carcinomas (OEC) with urothelial-like morphology, and 49 high-grade urothelial carcinomas (HGUC). MDM2 IHC was considered positive with diffuse (>25%) nuclear reactivity; in cases of patchy staining (10-25% nuclear reactivity), MDM2 was considered equivocal. Positive staining in <10% of cells was considered negative. In cases with positive or equivocal staining, MDM2 amplification was evaluated by fluorescence in-situ hybridization (FISH). Three MBTs (75%) showed diffuse nuclear reactivity for MDM2 by IHC, a finding corroborated by amplification of MDM2 in all three cases. One MBT and 2 BLBTs showed equivocal MDM2 IHC, but all three were negative for MDM2 amplification. The final BLBT, as well as all BBTs, HGSC, OEC, and HGUC, were negative for MDM2. In conclusion, our limited cohort confirms MDM2 amplification in MBT and suggests that MDM2 IHC may have an influence in rare diagnostically challenging cases.

Recurrent urothelial carcinoma-like FGFR3 genomic alterations in malignant Brenner tumors of the ovary

Malignant Brenner tumor is a rare primary ovarian carcinoma subtype that may present diagnostic and therapeutic conundrums. Here, we characterize the genomics of 11 malignant Brenner tumors, which represented 0.1% of 14,153 clinically advanced ovarian carcinomas submitted for genomic profiling during the course of clinical care. At the time of molecular profiling, there was no evidence of a primary urothelial carcinoma of the urinary tract in any case. Cases with transitional-like morphologic features in the setting of variant ovarian serous or endometrioid carcinoma morphology were excluded from the final cohort. Malignant Brenner tumors exhibited CDKN2A/2B loss and oncogenic FGFR1/3 genomic alterations in 55% of cases, respectively; including recurrent FGFR3 S249C or FGFR3-TACC3 fusion in 45% of cases. FGFR3-mutated cases had an associated benign or borderline Brenner tumor pre-cursor components, further confirming the diagnosis and the ovarian site of origin. Malignant Brenner tumors were microsatellite stable, had low tumor mutational burden and exhibited no evidence of homologous recombination deficiency. PIK3CA mutations were enriched with FGFR3 alterations, while FGFR3 wild-type cases featured MDM2 amplification or TP53 mutations. The FGFR3 S249C short variant mutation was absent in 14,142 non-Brenner, ovarian carcinomas subtypes. In contrast to malignant Brenner tumors, FGFR1/2/3 alterations were present in ~5% of non-Brenner, ovarian serous, clear cell and endometrioid carcinoma subtypes, most often as FGFR1 amplification in serous carcinoma or FGFR2 short variant alterations in clear cell or endometrioid carcinomas, respectively. Finally, malignant Brenner tumors had overall distinct genomic signatures compared to FGFR-mutated ovarian serous, endometrioid, and clear cell carcinoma subtypes. This study provides insights into the molecular pathogenesis of malignant Brenner tumors, contrasts the extent of FGFR1/2/3 alterations in ovarian serous, clear cell and endometrioid carcinomas and emphasizes the potential value of novel and FDA-approved, anti-FGFR inhibitors, such as erdafitinib and pemigatinib, in refractory, FGFR3-mutated malignant Brenner tumors.