Balancing risk in a patient with primary bone histiocytic sarcoma during pregnancy: Case report and review of the literature.

INTRODUCTION AND IMPORTANCE: Histiocytic sarcoma (HS) is a rare, aggressive malignant neoplasm of hematopoietic cell origin. Primary HS of the proximal humerus, without involvement of lymph nodes or bone marrow, or systemic features, is very rare. CASE PRESENTATION: We report a rare case of primary bony HS of the proximal humerus without bone marrow involvement in a healthy 33-year-old pregnant woman. She was successfully treated with surgical resection during pregnancy and radiotherapy post-delivery. CLINICAL DISCUSSION: This is the first report of a patient with primary bony HS during pregnancy. This highlights the fact that although HS is a neoplasm of hemolymphoid cell lineage, it frequently arises in non-lymphoid organs. CONCLUSION: This case emphasizes the importance of a multidisciplinary approach and the need for balancing treatment risk in a patient with primary bone HS during pregnancy.