Fibrous Hamartoma of Infancy : Differential

Comments:
Differential Diagnosis of Fibrous Hamartoma of Infancy (FHI) (continued from the previous image):

Giant Cell Fibroblastoma: About 25% of cases of FHI have hyalizined collagenous areas with cracking artifact forming slit-like spaces lined by flattened tumor cells. This creates a pseudoangiomatous appearance reminiscent of giant cell fibroblastomas. However, FHI lacks PDGFRB rearrangements, unlike giant cell fibroblastoma.

Sarcomas: Rare (two) cases of FHI containing sarcomatous areas have been reported. Such cases must be distinguished from other pediatric sarcomas. The differential diagnosis includes spindle cell rhabdomyosarcoma (positive for desmin, myogenin, and MyoD1) and infantile fibrosarcoma (ETV6 gene rearrangements).