Interdigitating dendritic cell sarcoma of pleura, diagnostic challenges of a rare disease.

Interdigitating dendritic cell sarcoma (IDCS) is an extremely rare subtype of dendritic cell tumour. The solitary lymph node disease is most commonly seen, but may occasionally present extranodally in skin, intestines, soft tissue, liver or spleen. Here we present a case of IDCS in pleura in 53-year-old man, who presented with loss of appetite and chest pain. The initial biopsy was inconclusive. The patient was started on anti-tubercular treatment considering the higher prevalence of the disease in this part of the world. However, the symptoms worsened after 2 months and repeat PET-CT scan revealed extensive FDG avid lesions in the multiple sites in the body. Repeat PET guided biopsy confirmed this rare IDCS neoplasm. Diagnostic challenges of this rare tumour are discussed. © The Japan Society of Clinical Oncology 2021.