The utility of PU.1 immunohistochemical marker in differentiating granular cell tumor from oral histiocytic lesions.

BACKGROUND

The histogenesis of granular cell tumors (GCTs) was once a subject of debate. Current evidence favors a Schwann cell origin, although the recurrent expression of macrophage-associated antigens contributed to earlier controversy. This study aims to evaluate the expression of the histiocytic marker, PU.1, in oral histiocytic lesions compared with GCT to contextualize these findings within the neural versus histiocytic lineage debate, as well as to assess BRAF V600E and ALK-1 expression in these entities.

STUDY

DESIGN

Archived oral lesions, including Langerhans cell histiocytosis (n = 1), verruciform xanthoma (n = 5), GCT (n = 5), xanthogranuloma (n = 2), and benign fibrous histiocytoma (n = 4), were analyzed by immunohistochemistry for PU.1, CD68, BRAF V600E, and ALK-1.

RESULTS

PU.1 demonstrates strong intensity and a mild-to-diffuse distribution in nuclear staining among all histiocytic lesions (Langerhans cell histiocytosis, verruciform xanthoma, xanthogranuloma, and benign fibrous histiocytoma) but was consistently negative in the neoplastic cells of GCT. CD68 was positive in all cases. No lesions exhibited BRAF V600E or ALK-1 immunoreactivity.

CONCLUSIONS

The absence of PU.1 expression in GCTs supports a nonhistiocytic origin; furthermore, none of the oral histiocytic lesions or GCTs examined demonstrate an etiological association with BRAF V600E or ALK-1 mutations.