Interobserver variability by pathologists in the distinction between cellular fibroadenomas and phyllodes tumors

Area of Science:

• Oncology
• Pathology
• Surgical Pathology

Background:

• Cellular stroma fibroepithelial lesions are often called cellular fibroadenomas.
• Criteria to distinguish cellular fibroadenomas from phyllodes tumors are subjective and vague.
• Clinical implications and surgical management differ between these lesions.

Purpose of the Study:

• To assess the diagnostic agreement among expert breast pathologists for challenging fibroepithelial lesions.
• To evaluate the reliability of current criteria in differentiating cellular fibroadenomas from phyllodes tumors.
• To explore diagnostic consensus when categorizing lesions into broader groups.

Main Methods:

• Retrospective review of 21 challenging fibroepithelial lesions.
• 10 specialist breast pathologists evaluated slides and clinical data.
• Participants used World Health Organization criteria for phyllodes tumors.

Main Results:

• Uniform agreement was reached in only 2 of 21 cases.
• When grouping fibroadenomas and benign phyllodes tumors separately from malignant types, 100% agreement occurred in 53% of cases.
• 90% agreement was achieved in 79% of cases under this broader classification.

Conclusions:

• Distinguishing cellular fibroadenomas from phyllodes tumors poses significant challenges, even for experts.
• There is substantial agreement in classifying lesions as either benign fibroepithelial tumors or malignant phyllodes tumors.
• Further research is needed to clarify clinical significance and improve differentiation, particularly for borderline and malignant phyllodes tumors.