Skip to 0 minutes and 15 secondsHow does pathology help the cancer patient? Pathology aims to help in diagnosis and predicting what the outcome or prognosis will be for a patient and in predicting what treatments might work for that patient and their tumor. Pathology can thus yield information, which is diagnostic or prognostic or predictive for treatment. Pathology is involved once a tissue or cell sample is taken. Before this, the patient has developed symptoms and attended a doctor. If there is a surface lump, that may be sampled. If not, then imaging or other investigations may identify a lump or other abnormality, which is then sampled for pathology or cytology. What samples or specimens do we look at? Samples for cytology contain individual cells rather than intact tissue.
Skip to 1 minute and 13 secondsCell samples are collected by draining fluid or putting a needle into a lump, called fine needle aspiration. Samples for pathology for diagnosis are often biopsies. These are small, usually only a few millimetres in size. Pathology also receives larger specimens. As part of treatment, a whole lump or abnormal area may be removed along with surrounding normal tissue by surgery. This is called a surgical resection, and examples include removal of a breast lump or length of colon. So what happens to the samples? Specimens from the patient are put into fixative then sent to the pathology laboratory.
Skip to 2 minutes and 0 secondsThere the tissue is processed overnight then put into small blocks of paraffin wax, like a candle, from which thin sections can be cut and stained for examination under a microscope. The usual stain is hematoxylin and eosin, or H and E. This is the stain used for most of the microscopic images you have seen. All of a small specimen is processed and examined by microscopy. Larger specimens are examined carefully by naked eye and representative pieces of tissue taken. This can involve a lot of work. For example, pathologists will select 15 to 30 tissue blocks from a colorectal cancer resection for microscopy. This takes up to an hour for the naked eye examination and the same again for microscopy.
Skip to 2 minutes and 54 secondsThe basis of diagnostic pathology is appearance or morphology, but extra tests on the tissue based on DNA, RNA, or protein molecules are increasingly important and sometimes crucial, especially for prognosis and prediction of treatment. Immunohistochemistrly, IHC, is a test on tissue sections, which enables the detection of specific proteins. Positive staining is a brown stain. Many IHC markers have been developed, which are routinely used to help to diagnose and classify cancers. Examples are shown in the links provided. A few IHC markers provide prognostic or predictive information or both. ER and HER2 are good examples as described later in the breast cancer video. Molecular assays for DNA and RNA include fluorescent in situ hybridisation, FISH; PCR, polymerase chain reaction; and sequencing.
Skip to 4 minutes and 2 secondsFISH is a test on tissue sections. FISH detects large-scale changes in chromosomes, including translocations, amplifications, and deletions. These can be diagnostic in some cancers, especially lymphomas, leukemias, sarcomas, and glial tumours. The other molecular assays are discussed separately on the course. What do we say about the specimen? Pathologists assess patient samples in a systematic way with stepwise questions. First, does the specimen contain appropriate tissue for diagnosis? Second, is there a tumour and is it malignant? Third, what is the tumour type according to the cancer classification described before? So far, so good. We're familiar with these. But now fourth, what is the tumour grade? Tumour grade and tumour differentiation are the same.
Skip to 5 minutes and 2 secondsThey describe how closely the tumour resembles the corresponding normal tissue. Tumour grade can be prognostic. A well-differentiated or low-grade tumour looks more like normal tissue than a poorly-differentiated or high-grade tumour. Specific grading systems have been developed for some cancers. In breast cancer, the Nottingham Prognostic Index is highly prognostic as shown in the separate video. So fifth, what is the tumour stage? Tumour stage describes how far the cancer has spread. It is based on pathology or imaging or both. Like cancer type, there are classifications for cancer staging. In 1936, the surgeon, Cuthbert Dukes, developed a staging system, which divided colorectal cancer into three groups.
Skip to 5 minutes and 58 secondsDuke's staging remains highly prognostic and tells us how likely a patient is to survive at least five years. Currently, the TNM, or tumour node metastasis staging system, is the most widely used. It describes the presence and extent of tumour invasion in three categories. T for local tumour, N for lymph node, and M for metastatic site. Each T, N, or M category is assigned a number. The higher the number, the more the spread. The clinical stage comprises the individual numbers linked together. This can be integrated into an overall stage from one to four. We also consider whether diagnostic, prognostic, or predictive molecular testing is needed. If so, this is requested. Small samples do not permit all of these assessment steps.
Skip to 6 minutes and 58 secondsOften, cytology samples and biopsies enable the diagnosis of malignancy, but staging is not possible. And tumour classification and molecular testing may be difficult. Tumours are heterogeneous. That is, variable throughout. So small samples from a large tumour may not be absolutely representative, which raises further issues, especially for molecular testing. In this video, we've learned about cancer pathology in real patients. We've heard about cancer spread and symptoms. We've learned about how we sample and look at tumours, including tumour grading and staging and about extra tests. The patient is then discussed with their pathology reports at the multidisciplinary team meeting with other doctors, including surgeons, radiologists and oncologists, as well as nurses.
Skip to 7 minutes and 54 secondsThis helps decide the plan for investigation and treatment, and that's what you'll be hearing about in the next videos.
Pathology in the patient: part two
Part two of two. Dr Karin Oien describes the role of pathology in determining cancer diagnosis, treatment and prognosis.
© University of Glasgow