# A Hierarchical Feature-Based Methodology to Perform Cervical Cancer Classification
## 2 Materials and Methods
### Database  
This work deals with two databases of cervical cells: (i) Herlev, well known and used in the literature, and (ii) CRIC, a new database with nucleus and cell segmentation results in smear images.  
The Herlev database [13] ([[http://mde-lab.aegean.gr/index.php/downloads](http://mde-lab.aegean.gr/index.php/downloads)]([http://mde-lab.aegean.gr/index.php/downloads](http://mde-lab.aegean.gr/index.php/downloads)) (accessed on 24 January 2021)) is collected at the Department of Pathology of Herlev University Hospital and the Department of Automation at the Technical University of Denmark. It consists of 917 single cervical cell images, divided into seven classes: superficial squamous epithelial; intermediate squamous epithelial; columnar epithelial; mild, moderate, and severe squamous non-keratinizing dysplasia; and squamous cell carcinoma in situ intermediate. All images also have a label of their regions, nuclei, and cytoplasm. Figure 1 shows a Herlev example image (a) and its label (b).  
The CRIC Searchable Image Database ([[https://database.cric.com.br/](https://database.cric.com.br/)]([https://database.cric.com.br/](https://database.cric.com.br/)) (accessed on 24 March 2021)) comprises cervical cell images and it is being developed by the Center for Recognition and Inspection of Cells (CRIC) and aims to support the Pap smear analysis. It covers cervical cells of conventional cytology, based on the standardized and most-used worldwide nomenclature in the diagnosis area, the Bethesda System nomenclature.  
Currently, the CRIC database is divided into two collections: one containing only the marking of the cell's center (classification) and another containing the segmentation of the cell's nucleus and cytoplasm. In both cases, each cell also has its classification. Only the segmentation collection will be used in this work since the nucleus region's delimitation will be important for the methodology used. There are 400 images obtained from Pap smears, with 3233 segmentations. Figure 2 presents an example of a segmentation image.  
Table 1 shows each database division, indicating the nuclei's categories and classifications. The number of nuclei in each class is also shown.  
In 1941, [PERSON] created the first classification system for normal and abnormal cells (class I, II, III, IV, and V). The second system was created by [PERSON] in 1953, separating the abnormal cells into mild, moderate, severe dysplasias, and carcinoma in situ. In 1967, [PERSON] proposed the division into CIN I, CIN II, and CIN III (Cervical Intraepithelial Neoplasia). To standardize the terminologies, in 1988, the \"Bethesda System\" was developed and approved by the National Cancer Institute in the USA; the system underwent reviews in 1991, 2001, and 2014. With this new nomenclature system, the current terms for the classification of abnormal squamous cells are ASC-US, LSIL, ASC-H, HSIL, SC [33; 34].  
Herlev's database uses the second classification system developed in 1953, while the CRIC base uses the most current classification system, the Bethesda System. In this sense, comparing the terminologies, mild dysplasia corresponds to LSIL, and moderate, severe dysplasia and carcinoma in situ corresponds to HSIL. Therefore, Herlev does not include the classifications of classes ASC-US, ASC-H, and SC used in the laboratory routine today.  
Our proposal uses information from the segmented nucleus to perform the classification of cells.  
Figure 1: Image example of the Herlev database.  
Figure 2: Segmentation example image of CRIC Searchable Image Database.