Diffuse Primary Amyloidosis of Retroperitoneum and Mesenteric Fat—Treatment and Long-term Follow-up.

Primary mesenteric and/or retroperitoneal amyloidosis is a rare entity with only few cases described in literature. Herein we describe an unusual such case in a 56-year-old man who presented with long-standing vague abdominal pain and lump. Abdominopelvic CT revealed numerous nodular variably calcifying deposits that were diffusely involving the mesenteric and retroperitoneal fat. Resected specimen pathology showed extracellular amyloid deposits replacing the adipocytes that were congophilic and exhibited apple green birefringence under polarized light. Kappa light chain restriction was noted in amyloid deposits on immunohistochemical studies. Myeloma studies did not reveal any significant abnormality. In view of the primary AL amyloidosis, the patient was started on cyclophosphamide, thalidomide, and dexona (CTD regimen). The patient responded well to the treatment with no further progression of the lesions. After 7 years of follow-up, the patient is alive with no systemic complications. [ABSTRACT FROM AUTHOR]