Extramedullary hematopoiesis: Clinical and cytological features

Hematopoiesis usually occurs in bone marrow in adults and when it occurs at sites except for bone marrow, it is termed as extramedullary hematopoiesis (EMH). It is usually found in organs, which are vigorously involved in fetal hematopoiesis, including liver, spleen, and lymph nodes. FNAC is easy and rapid method to diagnose EMH.

To study the spectrum of extramedullary hematopoiesis (EMH) on fine-needle aspiration cytology (FNAC).

A total of 10 patients who were diagnosed with EMH on FNAC were studied over a period of 5.5 years. Smears were stained with May Grunwald Giemsa (MGG) and Hematoxylin and Eosin (H and E). The detailed clinical and cytomorphological spectrum of EMH were studied.

The mean age of the patient was 42.5 years, with age ranging between 14 and 78 years. The commonest site of EMH was lymph node (n = 8, 80%) followed by paravertebral area (n = 2, 20%). Clinical diagnosis was EMH in just one case. Mean hemoglobin of the patient was 7.9 g/L. Bone marrow examination was available in 6 cases. On FNAC, we saw variable mixture of bone marrow elements including megakaryocytes (2.6%, 0-6%), myelocytes and metamyelocytes (29.2%, 18-33%), erythroid precursors (3.2%, 0-7%), polymorphs (21.7%, 10-36%), blasts (1.1%, 0-4%), eosinophils (2.5%, 0-7%), and lymphocytes (39.7%, 21-60%).

Cytopathologists must be alert of the clinical as well as cytological spectrum of extramedullary hematopoiesis for greater accuracy in diagnosis and to escape pitfalls in its diagnosis.