Fluorescent In Situ Hybridization in Surgical Pathology Practice

In Situ Gene Expression in Native Cryofixed Bone Tissue

Bone is a very complex tissue that is constantly changing throughout the lifespan. The precise mechanism of bone regeneration remains poorly understood. Large bone defects can be caused by gunshot injury, trauma, accidents, congenital anomalies and tissue resection due to cancer. Therefore, understanding bone homeostasis and regeneration has considerable clinical and scientific importance in the development of bone therapy. Macrophages are well known innate immune cells secreting different combinations of cytokines and their role in bone regeneration during bone healing is essential. Here, we present a method to identify mRNA transcripts in cryosections of non-decalcified rat bone using in situ hybridization and hybridization chain reaction to explore gene expression in situ for better understanding the gene expression of the bone tissues.

Expression of CTAG1B clone EPR13780 versus DDIT3 gene rearrangement distinguishes myxoid liposarcoma from its mimics with detection of novel DDIT3 gene copy number variations

Myxoid liposarcoma (MLPS) has different patterns that are often difficult to distinguish from other soft tissue lesions. MLPS is characterized by a reciprocal translocation involving the DNA Damage Inducible Transcript 3 gene (DDIT3) that can be detected using fluorescent in situ hybridization (FISH). Recently, the marker for cancer testis antigen 1b (CTAG1B) was found to be expressed in MLPS. The aim of the present study was to assess the potential use immunohistochemistry (IHC) for CTAG1B expression and DDIT3 rearrangement to diagnose MLPS and distinguish it from similar lesions. Out of 29 cases including MLPS and its mimics, CTAG1B was expressed in 92.86% of cases of MLPS and 20% of its mimics. DDIT3 rearrangement was 100% sensitive and 92.86% specific in distinguishing MLPS from its mimics. The DDIT3 rearrangement was found to be more sensitive but less specific than cytoplasmic expression of CTAG1B marker. DDIT3 polysomy and amplification were detected in some cases. Therefore, both CTAG1B expression and FISH for DDIT3 gene can be used to distinguish MLPS from similar tumors. The use of both immunohistochemistry for CTAG1B in addition to DDIT3 gene rearrangement detection by FISH was more specific than using either of them alone. However, the DDIT3 gene rearrangement alone was the most sensitive test for distinguishing MLPS from its mimics.

Optimized workflow for digitalized FISH analysis in pathology

BACKGROUND

Effective workflow management in a diagnostic pathology laboratory is critical to achieve rapid turnover while maintaining high quality. Fluorescence in situ hybridization analysis (FISH) is the preferred technique for detecting single chromosomal aberrations in diagnostic surgical pathology.

MATERIAL AND METHODS

FISH analysis applying a rapid hybridization protocol and using an automated whole-slide fluorescence scanning device (3DHISTECH, Sysmex, Switzerland) were implemented in our workflow. By analyzing 42 diagnostic cases, effects of two different scanning profiles on scanning time, and device memory usage were investigated. Manual signal counting (CaseViewer) and software based signal counting (FISHQuant) were compared.

RESULTS

The two scanning profiles, both including a Z-stack function, differed in their exposure time and digital gain. The "low profile" setting (LP) resulted in a significantly shorter scanning time and lower storage volume compared to the "high profile" (HP) setting, making the LP ideal for routine applications. Both signal counting methods (manual versus software based) provided similar cut-offs on a test-cohort of 13 samples.

CONCLUSION

Scanning FISH slides provides good picture quality, reduces the analysis time and allows easy picture archiving and facilitates remote diagnostics, allowing an effective workflow.

Clinical Utility of In Situ Hybridization Assays in Head and Neck Neoplasms

Head and neck pathology present a unique set of challenges including the morphological diversity of the neoplasms and presentation of metastases of unknown primary origin. The detection of human papillomavirus and Epstein-Barr virus associated with squamous cell carcinoma and newer entities like HPV-related carcinoma with adenoid cystic like features have critical prognostic and management implications. In salivary gland neoplasms, differential diagnoses can be broad and include non-neoplastic conditions as well as benign and malignant neoplasms. The detection of specific gene rearrangements can be immensely helpful in reaching the diagnosis in pleomorphic adenoma, mucoepidermoid carcinoma, secretory carcinoma, hyalinizing clear cell carcinoma and adenoid cystic carcinoma. Furthermore, molecular techniques are essential in diagnosis of small round blue cell neoplasms and spindle cell neoplasms including Ewing sarcoma, rhabdomyosarcoma, synovial sarcoma, biphenotypic sinonasal sarcoma, dermatofibrosarcoma protuberans, nodular fasciitis and inflammatory myofibroblastic tumor. The detection of genetic rearrangements is also important in lymphomas particularly in identifying 'double-hit' and 'triple-hit' lymphomas in diffuse large B cell lymphoma. This article reviews the use of in situ hybridization in the diagnosis of these neoplasms.