Divergent differentiation in malignant melanomas: a review

Area of Science:

• Pathology
• Oncology
• Dermatopathology

Background:

• Malignant melanoma is a skin cancer that can exhibit diverse cellular features.
• Divergent differentiation, or metaplastic change, involves the development of non-melanocytic components within melanoma.
• This phenomenon can lead to diagnostic challenges for pathologists.

Purpose of the Study:

• To review and discuss the diagnostic issues related to divergent differentiation in malignant melanoma.
• To document the various types of non-melanocytic cell or tissue components observed in melanomas.
• To highlight the importance of specific diagnostic tools in identifying these rare changes.

Main Methods:

• Literature review of reported cases of divergent differentiation in malignant melanoma.
• Analysis of morphological, immunohistochemical, and ultrastructural features.
• Discussion of diagnostic criteria and potential pitfalls.

Main Results:

• Divergent differentiation in melanoma is a rare event.
• Reported differentiation types include fibroblastic, Schwannian, smooth muscle, rhabdomyosarcomatous, osteocartilaginous, ganglionic, neuroendocrine, and epithelial.
• Diagnostic uncertainty can arise due to the unusual morphology.

Conclusions:

• Divergent differentiation in malignant melanoma is a rare but recognized entity.
• Accurate diagnosis relies on a combination of histopathology, immunohistochemistry, and electron microscopy.
• The clinical significance and underlying mechanisms of this phenomenon require further investigation.