Surgical Pathology Criteria

Pleomorphic Hyalinizing Angiectatic Tumor

Differential Diagnosis

Ancient Schwannoma Pleomorphic Hyalinizing Angiectatic Tumor
S100 positive S100 negative
CD34 negative on large cells CD34 80% positive on large cells
Usually encapsulated Microscopically infiltrative border
Vessels usually lack fibrin Fibrin frequent in and around vessels
Both schwannomas and PHAT may show pleomorphic cells with hyalinization and clusters of dilated vessels in a mitotically inactive tumor


MFH Pleomorphic Hyalinizing Angiectatic Tumor
Mitotic figures present, frequently atypical Mitotic figures rare
CD34 negative CD34 80% positive on large cells
Usually deep soft tissue Usually subcutaneous
Overall high cellularity Lacks high cellularity overall
Both MFH and PHAT may have increased Factor 13a positive cells


Pleomorphic Lipoma Pleomorphic Hyalinizing Angiectatic Tumor
No intracytoplasmic hemosiderin Intracytoplasmic hemosiderin
No aggregates of large vessels Aggregates of vessels with hyalinized walls and fibrin
Ropy collagen No ropy collagen
Restricted to back of neck, upper back and shoulders Various locations
Both are CD34 positive


Hemosiderotic Fibrohistiocytic Lipomatous Lesion has been proposed by Folpe and Weiss to represent early phase PHAT

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