Coexistence of acute severe leukocytosis and anaplastic lymphoma kinase-positive histiocytic sarcoma, a rare entity with an unusual presentation: A case report

Soft tissue sarcomas are rare cancers and most cases are metastatic at the time of diagnosis. Although the chances of survival are good with surgical treatment in the early stages, systemic treatment in the advanced stages is only associated with a survival duration of similar to 12 months. Alterations in the anaplastic lymphoma kinase (ALK) gene are becoming increasingly recognized as pan-cancer indicators in solid tumors. However, little is known regarding the molecular spectrum of ALK-positive histiocytosis. Molecular treatments, including ALK inhibitors, are potential treatment options. The present case report describes an aggressive ALK-positive soft tissue sarcoma with intracardiac metastases and severe leukocytosis responding to ALK inhibitors. The patient initially responded to crizotinib but required alectinib due to central nervous system progression. The patient has shown a near-complete response and remained stable for 2 years; however, there has been recent lymph node progression.