title: Poorly differentiated clusters (PDC) in colorectal cancer: what is and ought to be known.
abstract: BACKGROUND
  The counting of poorly differentiated clusters of 5 or more cancer cells lacking a gland-like structure in a tumor mass has recently been identified among the histological features predictive of poor prognosis in colorectal cancer.
  
  
  METHODS
  Poorly differentiated clusters can easily be recognized in the histological sections of colorectal cancer routinely stained with haematoxylin and eosin. Despite some limitations related to specimen fragmentation, counting can also be assessed in endoscopic biopsies. Based on the number of poorly differentiated clusters that appear under a microscopic field of a ×20 objective lens (i.e., a microscopic field with a major axis of 1 mm), colorectal cancer can be graded into malignancies as follows: tumors with <5 clusters as grade 1, tumors with 5 to 9 clusters as grade 2, and tumors with ≥10 clusters as grade 3. High poorly differentiated cluster counts are significantly associated with peri-neural and lympho-vascular invasion, the presence of nodal metastases or micrometastases, as well as shorter overall and progression free survival to colorectal cancer.
  
  
  CONCLUSIONS
  The morphological aspects and clinical relevance of poorly differentiated clusters counting in colorectal cancer are discussed in this review.
authors.affiliation: Department of Diagnostic Medicine and Public Health, University of Modena and Reggio Emilia - Section of Pathology, Via del Pozzo, 41124, Modena, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Reggiani Bonetti
authors.affiliation: Department of Pathology, University of Messina, Via Consolare Valeria, 98125, Messina, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Barresi
authors.affiliation: Department of Diagnostic Medicine and Public Health, University of Modena and Reggio Emilia - Section of Pathology, Via del Pozzo, 41124, Modena, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Bettelli
authors.affiliation: Department of Diagnostic Medicine and Public Health, University of Modena and Reggio Emilia - Section of Internal Medicine, Via del Pozzo, 41124, Modena, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Domati
authors.affiliation: CURML, chemin de la Vulliette 4, 1000, Lausanne, 25, Switzerland. cristian.palmiere@chuv.ch.
authors.forename: Cristian
authors.initials: C
authors.lastname: Palmiere
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D001706:Biopsy; D002452:Cell Count; D002454:Cell Differentiation; D015179:Colorectal Neoplasms / Q000737:chemistry / Q000401:mortality / Q000473:pathology* / Q000628:therapy; D018450:Disease Progression; D018572:Disease-Free Survival; D006801:Humans; D008207:Lymphatic Metastasis; D060787:Neoplasm Grading; D009361:Neoplasm Invasiveness; D061206:Neoplasm Micrometastasis; D011237:Predictive Value of Tests
chemical_list: D014408:Biomarkers, Tumor
keywords: Colorectal cancer; Poorly differentiated clusters; Tumor grading