Atypical PIK3CA Positive Hemangioma Refractory to Propranolol

A newborn presented with a lateral right eye proliferating vascular tumor, with characteristics consistent with infantile hemangioma by examination and imaging. The lesion was refractory to therapeutic dosing of oral propranolol, with worsening mass effect in the upper eyelid threatening hemianopsia. A near total surgical resection was completed. Histologic findings were mostly consistent with infantile hemangioma with some atypical areas of larger serpiginous, ectatic vessels identified. Immunostaining demonstrated strong CD34+, CD31+, and glucose transporter type 1 immunoreactivity and D2-40 immuno-negativity. Genetic sequencing revealed a pathogenic somatic PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha) variant (p.His1047Gln) at 8.3% allele frequency. Despite continued postoperative propranolol therapy, the lesion produced new mass effect over the right cheek. Alternative therapy with the mammalian target of rapamycin inhibitor, sirolimus, was initiated based on the novel genetic finding and lack of clinical response to standard therapy. The case demonstrates mosaic PIK3CA variant expression within a benign vascular tumor histologically and clinically sharing features of an infantile hemangioma.