Myeloid Sarcoma: An Unusual Case of Mediastinal Mass and Malignant Pleural Effusion with Review of Literature

Abstract

Myeloid sarcoma is an extramedullary tumor seen most commonly in patients with acute myeloid leukemia and less frequently in chronic myeloid leukemia, myelodysplastic syndrome and rarely, in an isolated form without any other underlying malignancy. Malignant pleural effusion in hematological malignancies is rare when compared with solid tumors. We present an unusual case of myeloid sarcoma in which a mediastinal mass with pleural effusion was the initial presentation. A 27 year old gentleman presented with complaints of fever, chest pain and swelling in the anterior chest wall for 6 months. Examination revealed a lump measuring 5 × 5 cm on the left side of the chest wall. Hematological evaluation showed hemoglobin-14.2 g/dL, platelet count-233 × 10(9)/L, TLC-117 × 10(6)/L with normal differential counts. Contrast enhanced computerised tomography (CECT) confirmed the presence of a soft tissue mass in the superior mediastinum abutting against the chest wall. Core biopsy was suggestive of myeloid sarcoma and immunohistochemistry was positive for myeloperoxidase and negative for CD3, CD 20 and CD 23. Pleural fluid analysis showed the presence of malignant cells. Bone marrow examination did not show an excess of blasts. A final diagnosis of extramedullary myeloid sarcoma with malignant pleural effusion was made. The patient was given induction chemotherapy (3 + 7 regimen) with daunorubicin and cytosine arabinoside. Repeat CECT done on day 28 showed complete resolution of pleural effusion and significant reduction in the size of mediastinal mass. The patient has successfully completed three cycles of consolidation therapy following which there has been complete resolution of the mass. He remains asymptomatic on close follow up.

Keywords: Acute myeloid leukemia; Malignant cytology; Myeloid sarcoma.

Fig. 1

Chest X ray PA view showing mediastinal widening with left sided moderate pleural effusion

Fig. 2

CECT chest showing soft tissue mass abutting against chest wall with left sided moderate pleural effusion

Fig. 3

PET scan revealed increased FDG avid uptake in the superior mediastinum

Fig. 4

Immunohistochemistry of trucut specimen of mediastinal mass showing positivity for myeloperoxidase and negativity for CD 20 and CD 23

Fig. 5

High power magnification of pleural fluid sample on staining shows myeloid cells comprised of blasts, myelocytes, metamyelocytes, neutrophils and eosinophils. Inset shows blasts having high nucleo-cytoplasmic ratio, immature chromatin, irregular nuclear margin and scanty to moderate cytoplasm, some with cytoplasmic blebbing (MGG, ×1000)

Fig. 6

Chest X ray PA view done on day 8 of induction therapy shows complete resolution of pleural effusion with no mediastinal widening

Fig. 7

Comparition of two chest X rays done a before chemotherapy with pleural effusion and b on day 8 of chemotherapy with resolution of pleural effusion

Fig. 8

Comparition of two CECT chest done a before chemotherapy with presence of large soft tissue mass and b on day 28 of chemotherapy with significant reduction of mass size