Histology and Pathology

What is a histological work-up for breast cancer?
Determining your type of breast cancer begins with a histological workup, a summary prepared by the pathologist after you undergo a biopsy. Essentially, the histological evaluation is the microscopic analysis of the chemical and cellular properties associated with a suspicious breast tumor. The pathologists here at Providence Saint John’s will also confirm the size of the breast tumor where necessary for breast cancer staging purposes. The histological evaluation is essential to determine the most effective treatment recommendations following surgery.

What is histology?
Histology is basically the microscopic study of living tissues. There are really four basic types of tissue in the body: epithelial tissue, muscle tissue, connective tissue, and nervous tissue. Breast cancer is a malignant transformation of epithelial tissue (usually glandular tissue). Fat (adipose) and fibrous tissue are both connective tissues, which may also form into suspicious lesions on that show up on a mammogram. The exact nature of the suspected tumor can almost always be confirmed on histological evaluation.

When a suspicious breast lesion appears on your mammogram or ultrasound, a biopsy sample will likely be taken from the lesion and sent for histological evaluation by the pathologist. Various amounts of tissue may be required, so we may perform either a fine needle, core, or excisional biopsy, but generally your Providence Saint John’s surgeon will try to remove as little tissue as possible while remaining confident that the sample is representative and taken from the right spot.

An initial biopsy sampling and analysis could be considered as an extension of the breast cancer screening process, where breast cancer is either confirmed positive or confirmed negative. Once breast cancer is confirmed by the pathologist, the breast cancer staging process begins. At that time, an additional sampling of breast tissue may be required for more extensive histological evaluation, and the lymph nodes will also be sampled in some manner.

Histological Grade

What is the histological grade of breast cancer?
Your Providence Saint Johns’ pathologist will be able to tell the type of breast cancer and if it is still confined to the breast ducts (DCIS); or whether it has reached infiltrative or invasive status. The pathologist will also be able to determine whether or not the cancer has metastasized to the lymph nodes in the axilla, based on an additional sample from that region.

The stage of your cancer is largely a function of the invasive or non-invasive status of the breast cancer, the size of the invasive component, and whether the cancer has spread to the lymph nodes or distant organs. The grade of the breast cancer is related more to the actual microscopic character of the cells in the breast tumor. Based on a variety of cellular features, the histological analysis helps determine the type of breast cancer as well as the grade. Histological classification of breast cancer, into essentially grades 1, 2, and 3, determines the aggressiveness of treatment because higher grades tend to correspond to poorer survival rates and prognosis.

How histological grade is determined.
What the pathologist will be considering is the degree of tubule formation within the tumor, meaning the number and differentiation of tubules; the mitotic count, or the rate and number of cell divisions; and nuclear pleomorphism which is basically the appearance of the cells and cell nuclei, in increasing amounts of variation and bizarre randomness. A combined score from the three observations determines the histological grade of the breast cancer. 

  • Grade 1 cancers have the lowest score and are usually well differentiated. They are usually the least aggressive.
  • Grade 2 cancers are intermediate in aggressiveness and are sometimes called moderately differentiated.
  • Grade 3 cancers are the most aggressive and are often poorly differentiated.

The pathologist may also note the presence and amount of necrosis, cell and tissue death and decay, and calcifications. Necrosis tends to be another indicator of an aggressive breast cancer.

Immunohistochemical markers
The use of steroid receptors (estrogen and progesterone) to predict breast cancer outcome and responsiveness to therapy has been used for many years now. In fact, the usual method for measuring the presence of steroid receptors in breast cancer tumors is by immunohistochemistry. There are no hard-and-fast rules for how to interpret the presence of various hormone and hormone receptor levels, but certain generally tendencies can be observed.

Estrogen and progesterone receptors
The most important hormonal indicators to identify are the positive presence of estrogen and progesterone receptors. Breast cancers that over-express high amounts of estrogen and progesterone receptors are likely to be more responsive to endocrine therapy treatment. Estrogen and progesterone receptors levels are detected in the nucleus of normal breast cells and many malignant cancer cells have retained the ability to express hormone receptors as well.

HER2: human epidermal growth factor receptor 2
Human epidermal growth factor receptor 2 (or HER2, or Her-2/neu/c-erb B2) has been an important aspect of breast cancer histology since about 1987. It has been shown that high levels of either HER2 gene amplification or protein expression tends to result in a poorer breast cancer prognosis. A monoclonal antibody therapy called Trastuzumab was developed to counter the effects of HER2, and its use has been shown to reduce rates of recurrence and mortality in HER2 positive early stage breast cancers. Additional targeted agents against Her2 (like Pertuzamab) have been used more recently in combination with Trastuzumab to achieve greater results.

Epidermal growth factor receptor 1
The epidermal growth factor receptor (EGFR or HER1) is a type 1 tyrosine kinase receptor that is expressed in normal breast tissue. Generally speaking, for this receptor to be present higher than expected levels of EGFR are accompanied by low levels of estrogen receptors, and other poor prognostic features. EGFR tends to be associated with grade III breast tumors.

This is a gene mutation in a gene important for controlling cell growth and death. For women who have breast cancer, this gene mutation can lead to a significantly increased risk of death. p53 is most commonly associated with tumors in premenopausal women. However, when it occurs in postmenopausal women, it was most commonly associated with a high body mass index.

B-cell lymphoma 2 (BCL2) is an antiapoptotic protein. Its presence can be an independent indicator of a favorable prognosis for early-stage breast cancer.

Molecular classification
One of the newer classifications of breast cancers is based on genes expressed in the tumor.  Luminal A and Luminal B are usually hormone receptor positive.  Luminal A breast cancers usually have an excellent outcome.  Her2neu breast cancers express the Her2neu gene.  Basal breast cancers are the most aggressive molecular sub-type and are usually hormone and Her2neu receptor-negative. They can also be triple negative cancers.

Basal breast tumor markers
Some breast tumors may express high levels of proteins that are not normally associated with epithelial cells, like the duct-lining cells most commonly associated with breast cancer, but are derived from basal or myoepithelial cells. There are a number of proteins associated with basal and myoepithelial gene expression, including cytokeratins 5 and 6, and 14, P-cadherin, and p63. Most of these tumors also have a corresponding low expression of ER, PgR, and HER2, and are considered to have a higher risk of metastasis.

Markers of breast cancer proliferation
An antigen called Ki-67 is expressed in the nucleus of neoplastic cells in all phases of a cell cycle, and is therefore thought to be a useful marker for high levels of proliferation. Notable changes in Ki-67 expression following a neoadjuvant treatment by endocrine or hormone therapy have been shown to be a useful predictor of long term outcome in some cases. If we can inhibit new cell growth, Ki-67 levels will also decrease, which tends to predict a good response to chemotherapy. Other proliferation markers in use include p21, p27, cyclin E, and cyclin D1.

However, it is still the presence of estrogen and progesterone receptors and Her2 that remain the most useful markers for determining the management of breast cancer. Epidermal growth factor receptors, Ki-67, and Topoisomerase II alpha have high potential as prognostic markers of breast cancer, while other markers such as P53, cyclin E, cyclin D1, p21, p27, Bcl2, bax, bcl-x, and survivin are still in an experimental phase, with limited clinical applicability.

In the future, microarray-based high-throughput technologies might be employed to look more closely at the molecular characteristics of breast cancers. Certain genetic/molecular features have been associated with an increased proclivity to metastasize. Certainly, the more we know about your tumor, the more aggressively we can treat it, and it is possible that in the near future these genetic and molecular features of a breast tumor might be included in the determination of histological breast cancer grade.

Several of the physicians and surgeons at the Margie Petersen Breast Center at Providence Saint John’s Health Center are also on faculty at the John Wayne Cancer Institute, and academically renowned research institute.