Question

part 2: how is mitotic index used in cancer studies?
mast cell tumors (mct) represent a cancer of mast cells, which are a type of white
blood cell involved in allergy and inflammation. mast cell tumors are the most
common skin tumor in dogs. older dogs are most commonly affected. some
predisposed breeds of dogs include boxers, boston terriers, bulldogs, pugs,
labrador retrievers, and golden retrievers.
mast cell tumors are classified as one of three different histologic grades (grades i, ii,
and iii). grade i mct act in a benign manner, and most can be cured with surgical
removal. grade iii mct are more aggressive tumors that are locally invasive and
have a high rate of spread (50 - 90%).
mitotic index (mi) is an indirect measure of cell proliferation that has been
demonstrated to be a strong predictor of outcome for several human and canine
cancers. the purpose of a study on dogs was to evaluate the utility of mi as a
predictor of survival in dogs with cutaneous mast cell tumors (mcts).
a single pathologist evaluated the he sections via light microscopy and generated an mi per 10 high - power (400×) fields
(hpfs). the region of the tumor sample with the highest overall mitotic activity was chosen for evaluation. a single count
of 10 hpfs was obtained for each tumor sample.

1. the data set below was sampled from a single specimen to illustrate

mitotic index = \\( \frac{\\# \text{ of cells in mitosis}}{\text{total } \\# \text{ of cells}} \times 100 \\)
how mitotic index can be determined.
the mitotic index is the ratio between the number of cells in mitosis
and the total number of cells. calculate the mi for each data set.

1. compare the mitotic index of the two types of tumors. what does this information tell you about the cells in the

sample?

Explanation:

Step1: Calculate the number of cells in mitosis for Grade 1 Tumor

Add the number of cells in each mitosis stage (excluding interphase): \(8 + 6+2 + 4=20\)

Step2: Calculate the total number of cells for Grade 1 Tumor

Add all cells: \(584+8 + 6+2 + 4 = 604\)

Step3: Calculate the mitotic index for Grade 1 Tumor

Use the formula \(MI=\frac{\text{\# of cells in mitosis}}{\text{total \# of cells}}\times100\). So \(MI=\frac{20}{604}\times100\approx3.31\%\)

Step4: Calculate the number of cells in mitosis for Grade 3 Tumor

Add the number of cells in each mitosis stage (excluding interphase): \(14 + 13+7 + 8=42\)

Step5: Calculate the total number of cells for Grade 3 Tumor

Add all cells: \(518+14 + 13+7 + 8 = 560\)

Step6: Calculate the mitotic index for Grade 3 Tumor

Use the formula \(MI=\frac{\text{\# of cells in mitosis}}{\text{total \# of cells}}\times100\). So \(MI=\frac{42}{560}\times100 = 7.5\%\)

Answer:

For Grade 1 Tumor:

• \(\text{\# in Mitosis}=20\)
• \(\text{Total \# of cells}=604\)
• \(\text{Mitotic Index}\approx3.31\%\)

For Grade 3 Tumor:

• \(\text{\# in Mitosis}=42\)
• \(\text{Total \# of cells}=560\)
• \(\text{Mitotic Index}=7.5\%\)