The Histology of Invasive Breast Cancer
There are a great number of different types of breast cancer, and quite frequently one encounters a combination of different types of breast cancer within the same patient.
A listing of the most common types of breast cancer
The Histology of Invasive Breast Cancer
There are a great number of different types of breast cancer, and quite frequently one encounters a combination of different types of breast cancer within the same patient.
A listing of the most common types of breast cancer would probably include:-
- tubular breast carcinoma
- mucinous breast carcinoma
- medullary breast carcinoma
- papillary breast carcinoma
- apocrine breast carcinoma.
The names given to different breast cancer types quite often refer to visual/microscopic characteristics of the malignant cells and cell formations.
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Invasive Tubular Carcinoma is recognizable as small regular tubules lined with a single layer of malignant cells.
Tubular carcinoma may contain other histologic elements, but usually an excess of 75% tubular elements is required for a confirmed diagnosis. A fine-needle aspiration is insufficient to differentiate between a ‘pure‘ tubular carcinoma, or one with mixed carcinogenic types.
Biopsies done from core-samples or excisions are required to make a thorough, confirmed diagnosis. Tubular carcinonoma sub-types with mixed pathologic features generally have a much poorer prognosis, largely determined by the most aggressive histologic element.
Well-differentiated infiltrating ductal carcinoma
Infiltrating ductal carcinoma is ‘graded‘ on a composite score of three main features: the relative number and shape of tubules, uniformity of nuclei, and mitosis or ‘cell-divisions‘. Grading is categorized as:
- moderately well-differentiated
- poorly differentiated
The more the histologic features are poorly differentiated, the higher the grade and more serious the prognosis. Highly differentiated cell formations tend to look more like normal cells, while poorly differentiated formations tend to be more bizarre and random in appearance, very different from normal, healthy cells.
The lesion below features well differentiated histologic elements, indicating and earlier stage of breast cancer development. We can also see how the cancer has spread from within the duct (intraductal) to other parts of the breast (infiltrating).
Mucinous carcinoma or Collagen Carcinoma
A mucinous or colloid carminoma is one in which the tumor is comprised primarily of mucus, more than 60%. The lesion appears as a collection of ‘lakes‘ of mucin, with floating ‘islands‘ of tumor cells scattered within them. Colloid Carcinoma generally has a good prognosis as it is not as prone to metastasis as other types of inflitrating breast cancers.
It is usually considered a low to medium grade, slow-growing type of cancer, even though, from a histological perspective, colloid carcimona tends to feature cancer cells that are poorly differentiated. In this sense it is a bit of an exception.
The image below is a colloid carcinoma, showing mucin-producing malignant cells, surrounded by yellow mucus, interspersed with strands of collagen fibers.
‘Mixed’ and ‘Pure’ mucinous carcinoma
Mucinous carcinoma is often further separated into two categories: “pure” mucinous carcinoma and “mixed” mucinous carcinoma. With colloid breast cancer the mucin forming cells are plump, containing little intracellular globules of mucin. Those globules are transported to the cell surface where they rupture, spilling the mucin to the outside of the cell. When the histological analysis reveals that all the mucin has spilled outside of the malignant cells (into the surrounding ‘lakes‘) it is called ‘pure‘ or ‘purely extracellular‘ mucin production.
However, when some of the mucin is not spilled outside the cell but remains within the immedate context of the malignant cells, this is called ‘mixed‘ mucinous carcinoma, where the mucin is not exclusively extracellular. It has thought that a ‘mixed‘ mucinous carcinoma has a more aggressive growth pattern than a pure presentation. Recent studies have also suggested a correlation between ‘pure‘ mucinous carcinoma and the presence of neuro-endorcine cells.
It is also now thought that a kind of ‘alternating pattern‘ in the orientation of mucin-producing cells suggests a lower grade carcinoma. If alternate mucin-producing cells drain towards the surrounding stroma, a ‘bond‘ of sorts occurs between the tumor and the stroma. The distinctive chemistry of this particular mucin, accumulating in the stroma surrounding the colloid cancer cells, provides for a kind of ‘cell-containment‘, slowing the spread of the cells and growth of the tumor.
Histology of Medullary Carcinoma
Medullary carcinoma gets its name on the basis of its microscopic appearance, which is similar to tissue found in the “Medulla Oblongata” region of the brain stem. Invasive medullary carcinoma usually appears in ‘sheets‘ of closely pack