Biostatistics Case Studies

CASE 11: Case Mortality Rates


The patient in case 1 visited her 49-year-old mother and told her about the biopsy and the results. Her mother remarked, "You know, maybe I should go and see my doctor, because my aunt died of breast cancer about my age." She sees her doctor, who palpates a large irregular firm fixed mass in the right breast as well as overlying skin with a rough, reddened appearance. There are enlarged, nontender axillary lymph nodes. Mammographically, the mass has irregular borders. A fine needle aspirate is performed of the mass and then a mastectomy is done. The lesional tissue is tested for estrogen-progesterone receptors and HER2.

The breast mass has irregular borders. The cut surface of the mass has a central irregular whitish scar. There are scattered foci of yellow to white necrosis and calcification. Axillary lymph nodes were also found to be enlarged and firm with similar cut surfaces. A frozen section confirms the diagnosis of malignancy

Microscopic sections of this neoplasm with overlying breast skin show intralymphatic cancer cells, accounting the clinical features of cutaneous inflammation and the "inflammatory carcinoma". This malignant neoplasm has cells which are arranged in nests, cords, and exhibit a poor attempt at gland formation. The stroma around the tumor-cell nests is mildly desmoplastic. Metastatic breast cancer is present in an axillary lymph node.


  1. What is the diagnosis?

  2. This is an infiltrating ductal carcinoma of breast with an inflammatory (dermal lymphatic) component and metastases to axillary lymph nodes.

  3. Why did the skin appear to be inflamed?

  4. This is caused by invasion of the carcinoma into the dermal lymphatics. "Inflammatory carcinoma" does not refer to a specific type or histologic subset of breast cancer, only to dermal lymphatic involvment.

  5. What is the significance of the family history?

  6. The risk of breast cancer is increased if a first degree relative, such as a mother, or aunt, has a history of breast cancer. The lifetime risk for breast cancer with affected first degree relatives is as follows:

    One relative less than 50 years13 - 21%
    One relative greater than 50 years9 - 11%
    Two relativesless than 50 years35 - 48%
    Two relativesgreater than 50 years11 - 24%

    Of course, BRCA-1 and BRCA-2 genes are the best known mechanisms for the appearance of early breast carcinoma that is familial. However, most of the important susceptibility genes have yet to be identified!

  7. Why would you want to know the results of testing for estrogen-progesterone receptors and HER2/neu in this lesion?

  8. If the carcinoma cells are positive for ER-PR, then there is an indication that hormonal therapy with an anti-estrogenic agent such as tamoxifen or an aromatase inhibitor such as letrozole will be of benefit in treatment. If the carcinoma cells are positive for HER2, the prognosis is probably not as good, but biotherapy with the monoclonal antibody trastuzumab can be of benefit.

  9. if there were 16 women in 1000 diagnosed with this disease last year and there were 39 in the same population previously diagnosed with this disease, what is the incidence and prevalence?

  10. The incidence of a disease is the rate at which new cases occur in a population during a specified period. The prevalence of a disease is the proportion of a population that are cases at a point in time. The incidence contributes to the prevalence. Thus, in this study, the incidence is 16 per 1000 and the prevalence is 0.055