This chapter suggests that considering the number of cells per section of a lymph node, mitoses are a relative rare event. Count data and the Poisson statistics that support the data are special examples of “counting” when numbers are too large for binominal proportion and too small for normal distribution, which probably represents one of the most common situations encountered in pathology. The methods were developed to allow for statistical calculations of rare events as are often encountered in pathology. The Poisson distribution is the unique properties of λ that allow for calculation of predicted events and comparison for statistical testing. As with any evaluation of data, understanding the form of the data is crucial to proper analysis. The chapter provides information of 10 patients who have a core needle biopsy called malignant peripheral nerve sheath tumor (MPNST).