Primary hepatic interdigitating dendritic cell sarcoma: A rarity unveiled.

Interdigitating dendritic cell sarcoma (IDCS) is a rare malignancy originating from dendritic cells, which participate in immune response activity as antigen-presenting cells by stimulating T lymphocytes. We report the case of a 24-year-old man who experienced an involuntary 20 kg weight loss over 2 months, combined with a steadily growing, painless lump in his right upper abdomen. Upon examination, a hard, nontender, immobile mass measuring 16 × 16 cm was found in the right hypochondrium. A massive, well-defined hypodense lesion covering all segments of the liver's right lobe was excised and was diagnosed as IDCS due to its characteristic histomorphological and immunohistochemical features.