Fibroepithelial Stromal Polyp of the Vulvovaginal Region as Part of the RB1 Family of Tumors: Friend or Foe?

Fibroepithelial stromal polyps (FSPs) are benign mesenchymal lesions occurring in the vulvovaginal region. Following the identification of loss of Retinoblastoma 1 (RB1) on immunohistochemical staining in routine practice, we stained a series of FSPs and performed additional fluorescence in situ hybridization (FISH) and copy number variation (CNV) sequencing to detect losses/deletions in the Retinoblastoma transcriptional corepressor 1 (RB1) gene. Fifteen FSP cases were stained for RB1, and subsequently, 9 cases were examined by FISH to detect a loss of RB1 (13q). Next, CNV sequencing was performed to assess genomic alterations. The mean age of the patients was 50 years. Loss of RB1 expression on immunohistochemistry was seen in 13 cases, and heterogeneous RB1 staining in the remaining 2 cases. FISH showed deletion of RB1 in all of the cases. CNV sequencing failed in almost all cases due to a low tumor content. Based on our findings, we hypothesize that FSPs are part of a spectrum of genetically related lesions, namely the 13q/RB1 family of tumors (which includes pleomorphic fibromas and spindle cell/pleomorphic lipomas). Due to the clinical, morphologic, and molecular overlap, we suggest that FSPs are pleomorphic fibromas occurring in the specialized stroma of the genital region.

Monosomy 22 and partial loss of INI1 expression in a biphasic synovial sarcoma with an Ewing sarcoma-like poorly differentiated component: Report of a case.

Poorly differentiated synovial sarcoma (PDSS) is a less common subtype of synovial sarcoma (SS) associated with a poor prognosis. We present a case of a SS with a poorly differentiated component that resembles Ewing sarcoma (ES). Initial immunohistochemical staining revealed a characteristic and strong expression of transducin-like enhancer of split 1 (TLE1) and weak to absent expression of integrase integrator 1 (INI1) staining. Stainings for keratin and epithelial membrane antigen (EMA) were negative in the tumoral lesion. Fluorescence In Situ Hybridization (FISH) analysis showed a rearrangement of the synaptotagmin (SYT) gene, confirming the diagnosis of SS. FISH analysis for the EWS RNA-binding protein 1 (EWSR1) gene revealed monoallelic loss of EWSR1. This finding was confirmed by an array comparative genomic hybridization (aCGH), showing complete loss of chromosome 22. Based on literature review, showing only a handful of cases of cytogenetically studied SS with loss of chromosome 22, this is probably a rare event in SS. Therefore, we assume that monoallelic loss of chromosome 22 cannot fully elaborate the underlying mechanism of the INI1 staining pattern in all SS, but it could account for the weak to absent INI1 staining in at least some cases.

Distinguishing score 0 from score 1+ in HER2 immunohistochemistry-negative breast cancer: clinical and pathobiological relevance.

OBJECTIVES: To investigate the clinical and pathobiological significance of distinguishing score 0 and score 1+ within the group of immunohistochemistry (IHC)-negative invasive breast cancers. METHODS: We studied HER2 status using both IHC and fluorescence in situ hybridization (FISH) in 150 consecutive breast tumors submitted to our laboratory after a negative IHC result in local testing centers. RESULTS: We were able to discern a group of score 0 tumors that had a lower HER2 copy number than the group consisting of score 1+ tumors. In contrast with the group of score 1+ tumors, HER2 FISH was consistently negative for both copy number-based and ratio-based tumors without equivocal results. CONCLUSIONS: In a setting with stringent quality assurance, score 0 and score 1+ tumors emerge as distinct and clinically important subgroups within the HER2 IHC-negative population.

Relationship between pathological features, HER2 protein expression and HER2 and CEP17 copy number in breast cancer: biological and methodological considerations.

AIMS: A few reports have assessed HER2 status in breast cancer by both dual-probe fluorescence in situ hybridisation (FISH) and immunohistochemistry (IHC) in an unselected and consecutive fashion, but CEP17 and HER2 copy number were not evaluated separately in these studies. Therefore, the aim of this study was to perform FISH testing for HER2 in a large number of breast tumours, irrespective of the IHC scores, which were also determined in all cases. METHODS: Both FISH and IHC were applied to 200 tumours from 196 consecutive patients who underwent resection of primary breast cancer with the sentinel procedure and/or axillary dissection. Not only the ratio, but also mean HER2 and CEP17 copy number were determined and used in statistical analyses to evaluate relationships between FISH, IHC and clinicopathological features. RESULTS: The amplification status based solely on HER2 signals was 98% concordant with results of dual-probe FISH. In non-amplified tumours, the mean CEP17 and HER2 copy number correlated, possibly because of cell cycling. Amplified tumours were histopathologically more aggressive than non-amplified tumours, and features of aggressiveness increased with the mean HER2 copy number. In both amplified and non-amplified tumours, a gene dosage effect was observed: an increase in the mean HER2 copy number was associated with a higher IHC score. CONCLUSIONS: This working method and analysis enabled new insights to be obtained into the pathobiology of HER2 in breast cancer. The findings may be helpful in optimising the methodology of HER2 testing.