Indeterminate Cell Histiocytosis of the Spine: A Case Report

Abstract

<b><i>Introduction:</i></b> Indeterminate cell histiocytosis is a rare neoplastic disease characterized by proliferation of dendritic cells that share morphologic and immunophenotypic features of Langerhans cells and non-Langerhans histiocytes. ICH lesions are typically restricted to the skin; however, there have been rare reports of extracutaneous and systemic involvement. <b><i>Case Presentation:</i></b> We describe a case of a 13-year-old female presenting with complaints of worsening lower back pain for 1 year. CT and MRI of the lumbar spine demonstrated a well-defined bony, lytic, expansile lesion of the posterior and mid-endplate of the L4 vertebra with mass effect on the thecal sac. The patient underwent L3–L5 decompression and fusion with surgical excision of the vertebral body tumor. Microscopic examination of the lesion showed benign fibrohistiocytic proliferation with giant cells, and immunohistochemical staining revealed a phenotype consistent with indeterminate cell histiocytosis (S100+ CD1a+ langerin−). <b><i>Discussion/Conclusion:</i></b> ICH is an extraordinarily rare neoplastic disease of dendritic cells that has a poorly understood pathogenesis. This case expands the spectrum of potential ICH extracutaneous involvement to now include the spine, a location previously undocumented in the literature in the pediatric population.