Extramedullary haematopoiesis in the kidney

Abstract

Extramedullary haematopoiesis (EMH) is the development of haematopoietic tissue outside the bone marrow and it most often occurs in the liver and spleen. Renal EMH is quite rare and there are very few case reports concerning the kidney. We describe two cases of ‘renal histologically documented EMH’ and, in particular, in the second of these two, the EMH tissue coexists with a clear cell renal carcinoma. Although rare, these clinical pictures raise some questions about the role of needle biopsy in the management of renal masses that present a diagnostic dilemma, especially in cases without involvement of other abdominal or intrathoracic organs.

Uncommon renal perihilar extramedullary haemopoiesis causing renal impairment

“…3 There are only a few cases reports in the literature describing a soft tissue lesion encasing the renal hilum similarly to our case report. [4][5][6] EMH can be hypermetabolic on PET/CT; 6 however, in our case report, there was no metabolic activity and therefore justifies the need for biopsy. The most important clinical consequence is that EMH involving the kidneys may lead to renal failure, due to either ureteric obstruction or extensive parenchymal involvement.…”

Extramedullary hematopoiesis in renal allograft

“…EMH has been reported in patients with various hematologic disorders, including chronic myeloid leukemia, essential thrombocytosis, myelofibrosis, sickle cell anemia, thrombocytopenia and polycythamia vera [ 1 – 8 ]. The most frequent site of occurrence is the reticuloendothelial system, i.e.…”

“…In their report, they included five additional cases from the literature that EMH had presented as renal mass, one of which was in a patient with myelofibrosis [ 2 ]. Since the first report by Moskovitz et al ., six additional cases of EMH in the native kidney have been reported in a patient with myelofibrosis, most of whom presented with acute renal failure [ 2 – 8 ]. To our knowledge, no case of EMH has been reported in kidney allograft in the English literature.…”

“…With regard to renal localization, Ricci et al . speculated two possibilities: residual niche for hematopoietic stem cell differentiation in the kidney or excess erythropoietin-driven stem cell migration and proliferation [ 8 ]. The morphology, immunoprofile and, occasionally, cytogenetic abnormalities have provided evidence that the cells infiltrating the kidney and other organs are the same cell population as the patient's bone marrow disease (as in our patient) suggestive of the neoplastic nature of the infiltrate.…”

“…Extramedullary hematopoiesis (EMH) can be one such example. EMH in native kidneys has been rarely reported in patients with hematopoietic neoplasms and in primary myelofibrosis [ 1 – 8 ]. Morphologically, EMH in the kidney can present as a mass-like lesion or as a diffuse infiltrate, the latter often offering a diagnostic challenge due to the morphological similarities with interstitial inflammation.…”