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August 23, 2017 - 10:49am | 83°F
   

Diagnostics

Laboratory testing for disease is targeted to three main areas:

  1. confirming a clinical suspicion (which may include making a diagnosis),
  2. excluding a diagnosis,
  3. assisting in the selection, optimization, and monitoring of treatment,
  4. providing a prognosis, and
  5. screening for a disease in the absence of clinical signs or symptoms.

The diagnosis of cancer begins with an overview of the affected tissue. For example, if a patient is suspected to have lung cancer, the mass in the lung is frequently evaluated for the presence of malignant cells. Access to tumor tissue may be easy (skin or blood for example), or evaluating the tissue may require more advanced procedures. Aspiration of cells from the tissue may be accomplished by fine needle aspiration (FNA) (lung mass or lymph nodes) or surgery may be required for larger tumors (such as gastrointestinal tumors).

As a result of our growing knowledge base of human genes and their role and function in pathology, we have moved toward molecular characterization of human disease. Molecular pathology facilitates disease diagnosis. Molecular assays, once ancillary and obscure, have now become essential to the pathologist and clinician in diagnosing disease. Molecular technologies improve patient care by decreasing the turnaround times for confirming diagnoses based on clinical observations. In many cases, molecular techniques allow identification of genetic aberrations that would not be detected by other methods. Technology is rapidly advancing to decrease the time required for these assays and their costs.

Molecular diagnostics changes the paradigm more towards preventive testing and treatment for cancer. Traditionally, diagnostics have been distinct from therapeutic development. Molecular medicine is changing that paradigm, as molecular markers become increasingly important for understanding disease biology, selecting and validating targets, and assessing the efficacy and safety of compounds under development. Molecular diagnostics have a much greater role in patient care.

At the Feist-Weiller Cancer Center, we offer the most comprehensive approach to the field for the diagnosis of cancer. The classification of lymphoma and leukemia has become very complicated and yet it is specific enough to be clinically relevant. Therefore, a simple morphologic diagnosis is no longer an acceptable clinical practice. New classification schema requires a comprehensive morphologic, immunophenotypic and molecular cytogenetic correlation to establish a final diagnosis. These parameters also provide guidance for treatment and predictors for prognosis. In general, pathologic review, immunophenotyping by flow cytometry and/or immunohistochemistry is the first step, which frequently provides and adequate diagnosis. Molecular genetic studies are being incorporated as an integral component in diagnosis, even when a diagnosis can be established by other means.

Flow cytometry is now a standard tool for immunophenotyping hematologic disease. Recent developments make the technology even more versatile for clinical use. Genetic and cytogenetic abnormalities define other subgroups of hematology neoplasms, and accordingly have been associated with unique biologic, clinical, and prognostic features. Hematologic malignancy is typically initiated by acquired genetic alterations, such as chromosomal translocations, mutations, and deletions. The diagnosis and prognosis of these cancers is commonly based or morphologic evaluation supplemented by analysis of molecular markers. New trends in gene-expressions profiling (e.g. microarrays) are genomic techniques that have proved effective in deciphering this biologic and clinical diversity (Staudt LM. Molecular diagnosis of the hematologic cancer. N Eng J Med 2003; 348:1777-85).

Albeit a plethora of information is building on hematologic neoplasms, solid tumors are not exempt from this genotypic approach to clinical management. For example, the Ewing sarcoma-specific translocation t(11;22), involving the EWS locus on chromosome 22 can now be detected using molecular cytogenetic techniques. Other soft tissue neoplasms, synovial sarcoma for example, carries the t(X;18)(p11.2;q11.2). This translocation is found in almost all synovial sarcomas (80%) regardless of the histologic type; it is not found in other spindle cell sarcomas, and very rarely detected in other tumors as malignant fibrous histyocytoma or fibrosarcomas. Rhabdomyosarcomas, the most common pediatric soft tissue sarcoma, is characterized by two pathognomonic translocations t(2;13)(q35;q14) and t(1;13)(p36;q14). These translocations lead to the formation of aberrant gene fusions, namely PAX3 - FKHR, in the t(2;13), and PAX7 – FKHR in the t(1;13), generating fusion transcripts. Genetic aberrations in lung, urothelial, thyroid, and gastrointestinal cancers are also detectable. Molecular cytogenetic approaches to the diagnosis of these diseases and clinical monitoring for residual disease are the standard of care in today’s laboratory medicine venue.

Contacts for additional help or inquires:

Mary Lowery Nordberg, PhD, Director
Molecular Pathology Laboratory
Department of Pathology / FWCC
Phone: (318) 675-8545
mlower@lsuhsc.edu

Feist-Weiller Cancer Center • 1501 Kings Highway • Shreveport, LA 71103
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