Myxoid atypical fibroxanthoma: a previously undescribed variant

Area of Science:

• Dermatopathology
• Oncology
• Histology

Background:

• Atypical fibroxanthomas (AFX) are dermal tumors common in sun-damaged skin of the elderly.
• Known histologic variants include spindle cell, clear cell, and osteoid types.
• Myxoid change has not been previously documented in AFX.

Observation:

• Four cases of AFX with myxoid change were identified over a 4-year period.
• All lesions were solitary, affecting elderly males on the head, neck, or upper extremities.
• Histology revealed cellular tumors with atypical pleomorphic and spindle cells in a myxomatous background, lacking junctional or epidermal components.

Findings:

• Tumor cells were negative for melanocytic and epithelial markers.
• Positive immunohistochemical staining was observed for CD10 (3/4 cases) and vimentin (4/4 cases).
• Myxoid change was a prominent feature in all reviewed cases.

Implications:

• Myxoid change in AFX is a rare variant that requires recognition.
• Awareness of this histological feature is essential for accurate diagnosis and avoiding misclassification of cutaneous tumors.
• This finding expands the spectrum of known histological variations in atypical fibroxanthomas.