Distinct Histological Patterns of Splenic Extramedullary Hematopoiesis in Myeloproliferative Neoplasms Correlate with Clinical Behavior.
Sonam Prakash, Ronald Hoffman, Sharon Barouk, Daniel M Knowles, Attilio Orazi. Weill Cornell Medical College, New York; Mount Sinai School of Medicine, New York
Background: Extramedullary hematopoiesis (EMH) is a feature of advanced stage disease in Philadelphia chromosome-negative myeloproliferative neoplasms (MPN). While previous studies have demonstrated that splenic EMH in MPN is clonal and distinguishable from reactive EMH, there are no studies evaluating histologic features of EMH in relation to clinical course.
Design: We studied 24 splenectomies with EMH from patients with MPN (14 primary myelofibrosis, 7 polycythemia vera, 3 unclassifiable). Routine H&E, reticulin and trichrome stains and immunohistochemistry (IHC) for myeloperoxidase, glycophorin C, CD42b, CD34, CD117 and CD8 were used to evaluate the hematopoietic cells and stromal elements. Clinical information was obtained from the clinical records and correlated with the morphologic findings.
Results: The splenic EMH cases (15 males, 9 females) ranged in age from 43 to 81 years (median 61 yrs). Erythropoiesis was largely intravascular, myelopoiesis was within the splenic cords and megakaryopoiesis was observed in both. The morphologic features of splenic EMH did not correlate with specific MPN subtypes. Three distinct histological patterns of EMH were recognized: diffuse (D)-EMH (12), nodular (N)-EMH (5), and mixed diffuse and nodular (M)-EMH (7). The average spleen weight was greater in M-EMH (4611g) as compared to that in D-EMH (3073g) and N-EMH (3218g). The preponderant lineage was myeloid in D-EMH, trilineage or erythroid in N-EMH and any combination of these in M-EMH. The stromal changes paralleled the histological pattern with absence of stromal alteration in D-EMH, stroma devoid of CD8(+) sinusoids in N-EMH and a combination of these in M-EMH. No other differences were observed by IHC between the 3 groups. The average duration of follow-up from initial diagnosis was 106 months (range 22 to 312 months). Fifteen of 24 patients were dead of disease: D-EMH 8/12 (66.6%), N-EMH 2/5 (40%), and M-EMH 5/7 (71.4%). Time to symptomatic splenomegaly was much shorter in patients with M-EMH (37 months) as compared with D-EMH (82 months) and N-EMH (75 months).
Conclusions: Splenic EMH in MPN shows distinct histological patterns that do not correlate with disease subtypes but appear to show a correlation with clinical behavior. M-EMH is associated with a more aggressive clinical course and poor outcome and N-EMH with the most favorable. Additional studies with a larger number of cases are required to verify these preliminary findings.
Monday, February 28, 2011 1:00 PM
Poster Session II # 179, Monday Afternoon