BEYOND CARCINOMA: UNMASKING PRIMARY HISTIOCYTIC SARCOMA OF THE ESOPHAGUS

Abstract

Background: Histiocytic sarcoma (HS) is a rare and aggressive hematopoietic malignancy arising from mature histiocytes. Primary involvement of the esophagus is exceptionally uncommon and often poses significant diagnostic challenges because of its clinical and histopathological resemblance to high-grade carcinomas and other poorly differentiated malignancies. Case Presentation: A 47-year-old woman presented with progressive dysphagia to solid foods for four months. Upper gastrointestinal endoscopy revealed an ulceroproliferative growth in the lower thoracic esophagus. Histopathological examination demonstrated a high-grade malignant neoplasm. Immunohistochemical analysis showed strong positivity for Vimentin, CD68, CD163, and CD4, with focal expression of EMA, PanCK, and LCA, while markers including p63, p40, S100, HMB45, SOX10, MPO, CD117, DOG1, and TdT were negative. These findings established the diagnosis of histiocytic sarcoma. Staging ^18F-FDG PET/CT demonstrated intensely FDG-avid circumferential mural thickening involving the lower thoracic esophagus and gastroesophageal junction (SUVmax 28.2) with metabolically active regional lymphadenopathy. The patient received CHOP chemotherapy (cyclophosphamide, doxorubicin, vincristine, and prednisone). Follow-up ^18F-FDG PET/CT after three cycles demonstrated complete metabolic response with resolution of FDG uptake at both the primary site and involved lymph nodes. Conclusion: Primary histiocytic sarcoma of the esophagus is an exceptionally rare malignancy that may closely mimic high-grade carcinoma. Accurate diagnosis requires comprehensive immunohistochemical evaluation and correlation with imaging findings. This case highlights the diagnostic value of immunophenotyping and ^18F FDG PET/CT and demonstrates a favorable response to CHOP chemotherapy. Reporting such rare cases contributes to the limited literature and may aid in developing future diagnostic and therapeutic strategies.