PD-L1 expression in angiomatoid fibrous histiocytoma

Abstract

Angiomatoid fibrous histiocytoma (AFH) is a rare tumor of intermediate malignancy. Treatment options for unresectable and/or metastatic tumors are very limited. Immunotherapy with PD-1/PD-L1 inhibitors may be worth exploring. The aim of this study was to evaluate the expression of PD-L1 in AFHs. PD-L1 expression was assessed on 36 AFHs from 36 pediatric patients by immunohistochemical staining of PD-L1 (clone 22C3). Positivity was defined as membranous expression in ≥ 1% of either tumor or immune cells. The correlations between PD-L1 expression and clinicopathologic features were assessed. Two patients had lymph node metastasis. All patients underwent surgical resection; three of them also had systemic chemotherapy. Three patients had recurrence after initial resection; all patients were alive with a median follow-up of 2.5 years. Overall, twenty-two (61%) tumors were positively stained for PD-L1 and positivity was seen on both tumor and immune cells in eighteen of the 22 tumors. A positive correlation was found between tumor cell PD-L1 expression and CD8+ T-cell infiltration. There were no statistically significant differences between the status of PD-L1 expression and the clinicopathological features assessed. PD-L1 expression was identified in 61% of AFHs with a predominantly adaptive pattern. Our findings provide a rationale for future studies evaluating the potential of checkpoint immunotherapy for patients with unresectable and/or metastatic tumor.

Pulmonary Artery Angiomatoid Fibrous Histiocytoma Mimicking a Large Pulmonary Embolism

“…2,3,5 Microscopically, a thick fibrous pseudocapsule, infrequent mitoses, blood-filled endothelial-lined cystic cavities, and a rim of dense lymphoplasmacytic infiltrate suggest the diagnosis. 8,9 Fluorescence in situ hybridization analysis revealed rearrangement of EWSR, which was confirmed by RT-PCR as EWSR1-ATF1 fusion. First-line treatment for AFH is wide local excision with an approximate recurrence rate of 15% with metastases and mortality occurring in approximately 1% of patients.…”

“…The differential diagnosis of pulmonary artery AFH includes septic PE, pulmonary artery fibrous tumor, sarcoma, and so on 2,3,5. Microscopically, a thick fibrous pseudocapsule, infrequent mitoses, blood-filled endothelial-lined cystic cavities, and a rim of dense lymphoplasmacytic infiltrate suggest the diagnosis 8,9. Fluorescence in situ hybridization analysis revealed rearrangement of EWSR, which was confirmed by RT-PCR as EWSR1-ATF1 fusion.…”