Splenic extramedullary haematopoiesis

Clinical History

Recent complaints of malaise. Past medical history included right mastectomy and radiotherapy for breast carcinoma 13 years previously. Clinical and laboratory examinations were normal. Imaging work-up (upper abdominal sonography and CT scan) revealed a focal splenic lesion.

Imaging Findings

The patient presented with complaints of malaise over the previous three months, without other associated symptoms. She had undergone right modified radical mastectomy and neoadjuvant radiotherapy for invasive lobular carcinoma 13 years previously, without evidence of loco-regional recurrence or distant metastases to date. Physical examination was unremarkable and laboratory findings were normal.

Imaging work-up of the patient consisted of an upper abdominal sonography and CT scan that revealed the presence of a focal splenic lesion. Based on the clinical data and imaging findings, a diagnosis of a metastatic lesion was suggested. On microscopic examination of the splenectomy specimen, two foci of extramedullary haematopoiesis (EMH) were found. Investigation was not able to demonstrate a myeloproliferative syndrome and we coudn't find any association between the inicial symptoms and the pathological findings.

Discussion

Extramedullary haematopoiesis (EMH) is a normal finding in the foetus and newborn until the age of five weeks, and can persist in the presence of anaemia. It is infrequent in adults, being associated with dysfunction or loss of bone medulla as a result of a chronic myeloproliferative disease, such as agnogenic myeloid metaplasia, polycythaemia vera, chronic myeloid leukaemia, or with haemolytic anaemias, such as thalassemia (mainly the major), and hereditary spherocytosis. It has been described in multiple locations with the liver and spleen being the most common; it has also been documented in the thorax, suprarenal glands, retroperitoneal fat, lymphatic and gastrointestinal systems, breast, skin and dura mater.

Recent reports favour the hypothesis that EMH in the spleen orginates from precursor cells displaced from the bone marrow rather than from activation of stem cells that have lain dormant in the spleen since foetal life. The sonographic patterns of splenic EMH are varied and non-specific, including simple splenomegaly, a hypoechoic lesion, solitary or multiple hyperechoic lesions, or a solid heterogeneous mass.

The differential diagnosis of a hyperechoic non-traumatic focal splenic lesion should include, besides metastases (in a patient with a known primary neoplasia), lymphoma, haemangioma, abscess, infarct and EMH. EMH is an extraordinarily rare event, as far as we can determine, with only three previous reports, none in the absent of haematological disease.

Differential Diagnosis List

Final Diagnosis

Splenic extramedullary haematopoiesis

URL:	https://www.eurorad.org/case/1298
DOI:	10.1594/EURORAD/CASE.1298
ISSN:	1563-4086