Cellularity of routinely prepared cell blocks : insights from an international study

Srebotnik-Kirbiš, Irena (author), Strojan Fležar, Margareta (author)

Objective: Formalin-fixed, paraffin-embedded (FFPE) cell blocks (CBs) are widely used for processing cytology specimens, but preparation methods remain variable and non-standardised. Low cellularity is a common limitation that may compromise diagnostic utility. This study aimed to evaluate the cellularity of routinely prepared CBs across different preparation methods, laboratories and sample types. Methods: Each laboratory in this multicentre observational study retrospectively assessed 50 consecutive CBs prepared using a single method. Cellularity of Haematoxylin and Eosin (H&E)-stained sections was semi-quantitatively evaluated by two independent reviewers per laboratory in four categories: acellular, low (≤ 100 cells), medium (100-500 cells) and high cellular (> 500 cells). The proportion of poorly cellular CBs (acellular + low cellular) was compared across methods, laboratories and sample types using non-parametric tests. Results: Cellularity was assessed for 1817 CBs prepared using Agar (22%), HistoGel (19%), Plasma-Thrombin (19%), Cellient (17%), In-house (15%) and Shandon/Epredia (8%) methods. The proportion of poorly cellular CBs ranged from 4% to 80% across laboratories (mean 27%, median 25%), with no consistent clustering by method. Median proportions by method ranged from 12% (Cellient) to 35% (Agar), but inter-method differences were not statistically significant (p > 0.05). Substantial variability was observed both across and within sample types and preparation methods. Conclusions: The study revealed marked variability in the proportion of poorly cellular CBs among preparation methods and laboratories, highlighting the need for improved processing and monitoring of CB adequacy.

• Language: English
• Keywords: cell block, cellularity, cytology, preparation of method
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: MF - Faculty of Medicine
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: Str. 214-221
• Numbering: Vol. 37 , iss. 3
• PID: 20.500.12556/RUL-184919
• UDC: 616:576
• ISSN on article: 0956-5507
• DOI: 10.1111/cyt.70065
• COBISS.SI-ID: 271666691
• Publication date in RUL: 17.07.2026

Record is a part of a journal

• Title: Cytopathology
• Shortened title: Cytopathology
• Publisher: Wiley
• ISSN: 0956-5507
• COBISS.SI-ID: 513812

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: celični blok, celularnost, citologija, metoda priprave