Ovarian Serous Carcinoma - Two-Tier System for Histologic Grading

 

Grading is based on the histologic features in the "worst" area of the tumor.

 

Primary histologic parameters:

(1) variation in size (based on ratio of largest to smallest nucleus)

(2) uniformity of nuclear shape

(3) chromatin pattern

 

Secondary histologic parameters (only used if primary histologic features are equivocal):

(1) mitotic index

Parameter	Low Grade	High Grade
variation in size	little	marked (nuclear size ratio >= 3)
nuclear shape	uniform round to oval with little variation	marked variation
chromatin	even to slightly irregular	marked variation
mitotic index	<= 12 mitoses per 10 hpf	> 12 mitoses per 10 hpf

 

where:

• The textual description does not include intermediate features. There are 2 ways to handle these values - (1) score them as high grade features or (2) assign an intermediate score. In the implementation points are assigned as 0 if low grade, 0.5 if intermediate and 1.0 if high grade. The primary 3 features are summed. If the score is >= 1.5 it is high grade, if <= 0.5 low grade, else (score 1.0) the grade is determined by the mitotic index.

• Hpf = high power microscopic field (40x objective). Using a count per square mm would probably be more precise.

• Both low grade and high grade tumors can show prominent nucleoli.

 

Performance:

• Malpica et al (2007) reported good interobserver and intraobserver performance.

 

Limitations:

• Multiple sections need to be examined and the least differentiated area selected for the grading.