Fluorescence in situ hybridization: a multitarget approach in diagnosis and management of urothelial cancer

"Indeterminate" UroVysion Fluorescence In Situ Hybridization Results

OBJECTIVES

UroVysion cases with one to three abnormal cells that do not meet the threshold for positivity may be better classified as "indeterminate." The aim of this study is to determine the incidence and clinical significance of these indeterminate UroVysion results.

METHODS

The UroVysion fluorescence in situ hybridization (FISH) results over a 4-year period in our institution were retrospectively analyzed. Follow-up of the initial UroVysion cases, including urine cytology or bladder biopsy performed within 12 months of the initial diagnosis of the result, was obtained from pathology reports.

RESULTS

A significant fraction (178 of 1,907, 9.3%) of the UroVysion cases had indeterminate results. Overall, the subsequent malignancy rate of the group with indeterminate UroVysion results (14 of 59, 23.7%) was higher than the group with normal results (48 of 319, 15.0%), although the difference was not significant (P = .124). For patients without a history of urinary tract neoplasm, the subsequent malignancy rate in the group with indeterminate results (7 of 18, 38.9%) was significantly higher than the group with normal results (16 of 103, 15.5%) (P = .044).

CONCLUSIONS

Our results support that indeterminate UroVysion FISH result may warrant closer clinical follow-up in patients without a history of urinary tract neoplasm. We suggest reporting these cases as "aneusomy of undetermined significance."

Role of Tetrasomy for the Diagnosis of Urothelial Carcinoma Using UroVysion Fluorescent In Situ Hybridization

CONTEXT

-UroVysion fluorescent in situ hybridization (FISH) is routinely used to detect urothelial carcinoma (UC). A positive threshold is defined as chromosome polysomy in 4 or more cells, which also includes tetrasomy, a natural product of cell division.

OBJECTIVES

-To evaluate tetrasomy for UC detection and explore the relation to the surgical diagnosis or patient history.

DESIGN

-The FISH was performed on 1532 urine samples from patients with cytology results and 4 or more years of follow-up. We created separate polysomy and tetrasomy categories and constructed receiver operating curves to determine appropriate thresholds using biopsy (n = 194) as the gold standard. Standard FISH and a novel assay integrating cytomorphology and FISH (Target-FISH) were compared. Matching tissue biopsies of urine samples with 10 or more tetrasomy cells were analyzed.

RESULTS

-No significant threshold was found for tetrasomy cells. Exclusion of tetrasomy from the polysomy category changed the threshold from 8.5 to 4.5 cells, increased specificity (59.2% to 78.9%), but reduced sensitivity (78.9% to 65.9%). In Target-FISH, the same approach yielded a specificity of 93.7% and sensitivity of 65.2%. Similarly, specificity improved significantly for low- and high-grade UC, but sensitivity decreased for low-grade UC. No evidence of UC was observed in 95% (52 of 55) of the patients referred for screening who had 10 or more tetrasomy cells by FISH. Matching biopsies for urines containing 10 or more tetrasomy cells showed few or no tetrasomy cells.

CONCLUSIONS

-Tetrasomy is a nonspecific finding frequently encountered in urine FISH and should be excluded from the polysomy classification. Target-FISH is an optimal approach, offering the ability to detect rare tetrasomy tumors.

Urine Cytopathology and Ancillary Methods

Urothelial carcinoma (UC) is the most common malignancy of the urinary tract. Cytology and cystoscopy are two of the most commonly used tests for screening and diagnosis of UC. However, the sensitivity of cytology for UC is less than ideal, while cystoscopy is an invasive and expensive procedure. The search for an accurate, sensitive, noninvasive, and cost-effective method for detecting UC has led to the development of ancillary studies using immunological and molecular methods.

DNA mimics for the rapid identification of microorganisms by fluorescence in situ hybridization (FISH)

Fluorescence in situ hybridization (FISH) is a well-established technique that is used for a variety of purposes, ranging from pathogen detection in clinical diagnostics to the determination of chromosomal stability in stem cell research. The key step of FISH involves the detection of a nucleic acid region and as such, DNA molecules have typically been used to probe for the sequences of interest. However, since the turn of the century, an increasing number of laboratories have started to move on to the more robust DNA mimics methods, most notably peptide and locked nucleic acids (PNA and LNA). In this review, we will cover the state-of-the-art of the different DNA mimics in regard to their application as efficient markers for the presence of individual microbial cells, and consider their potential advantages and pitfalls. Available PNA probes are then reassessed in terms of sensitivity and specificity using rRNA databases. In addition, we also attempt to predict the applicability of DNA mimics in well-known techniques attempting to detect in situ low number of copies of specific nucleic acid sequences such as catalyzed reporter deposition (CARD) and recognition of individual genes (RING) FISH.

[Fluorescence in situ hybridization. A new diagnostic dimension in cytology]

Fluorescence in situ hybridization (FISH) is a powerful method for the identification of chromosomal aberrations to improve the diagnostic performance of cytology. FISH is applicable to almost any type of cytological specimen irrespective of cell type, staining or fixation modality. Multi-target tests for the simultaneous analysis of four chromosomes or chromosomal loci improves the sensitivity of cytological diagnosis in bladder and lung cancer and is most helpful in equivocal cytology. FISH also allows a reliable distinction between malignant mesothelioma and reactive mesothelial cells. Specific translocations can easily be detected by FISH for precise diagnosis of lymphomas and sarcomas. Testing for HER-2 amplification has become a standard method to select patients with breast cancer for therapy with trastuzumab. Co-analysis of HPV and selected genes could become a useful approach in gynecological cytology. The spectrum of diagnostic FISH applications is continuously growing.

Diagnostic significance of allelic imbalance in cancer

Allelic imbalance (AI), a deviation from the normal 1:1 ratio of maternal and paternal alleles, occurs in virtually all solid and blood-borne malignancies. The frequency and spectrum of AI in a tumor cell reflects the karyotypic complexity of the cancer genome. Hence, many investigations have assessed the extent of AI to analyze differences between normal and tumor tissues in a variety of different organs. In this review, the authors describe established and emerging technologies used to assess the extent of AI in human tissues, and their application in the diagnosis of cancer. The four major methods to be reviewed represent powerful and widely used tools for the identification of allelic imbalances accompanying cancer initiation and progression. These are fluorescent in situ hybridization, comparative genomic hybridization, single nucleotide polymorphism arrays and the use of microsatellite markers. For each method, the authors provide a brief description of the approach and elaborate on specific studies that highlight its utility in the diagnosis of human cancers.