Haemophagocytic histiocytic sarcoma
The following are histopathology (H&E x400) sections from an enlarged spleen with multiple, poorly delineated nodules in an 8-year old Rottweiler that presented with regenerative anaemia.
Final Diagnosis
Splenic haemophagocytic histiocytic sarcoma
Discussion
Haemophagocytic histiocytic sarcoma (formerly known as malignant histiocytosis) is an uncommon malignant neoplasm in which the neoplastic histiocytes display erythrophagia and/or haemosiderin-accumulation resulting in progressive anaemia. The spleen is the most commonly affected organ but the liver, lungs, lymph nodes and bone marrow are also frequently involved. Generalised hepatosplenomegaly and lymphadenopathy are common clinical findings. Disease progression is typically rapid and unfortunately the prognosis is poor.