Myeloid sarcoma: an uncommon presentation of myeloid neoplasms; a case series of 4 rare cases reported in a tertiary care institute

Abstract

Myeloid sarcoma (MS) is a rare extramedullary neoplasm of myeloid cells, which can arise before, concurrently with, or following hematolymphoid malignancies. We report 04 such cases of MS, diagnosed in this institute over a period of 6 years, during various phases of their respective myeloid neoplasms/leukemias. These cases include MS occurring as a relapse of AML (Case 1), MS occurring as an initial presentation of CML (Case 2), MS occurring during ongoing chemotherapy in APML (Case 3), and MS presenting as a progression of MDS to AML (Case 4). In the absence of relevant clinical history and unemployment of appropriate immunohistochemical (IHC) studies, these cases have a high risk of being frequently misdiagnosed either as Non-Hodgkin's Lymphoma (NHL) or small round cell tumors or undifferentiated carcinomas, which may further delay their management, making an already bad prognosis worse. This case series has been designed to throw light on the varied presentation of MS and the lineage differentiation of its neoplastic cells through the application of relevant IHC markers along with their clinical correlation.

Keywords: Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Leukemia, Myeloid, Acute; Leukemia, Promyelocytic, Acute; Myelodysplastic Syndromes; Sarcoma, Myeloid.

Figure 1. A – Peripheral blood smear showing blasts (arrow). (Leishman's stain, 1000x); B – Bone marrow aspirate smear showing blasts of myeloid lineage (Leishman's stain,1000x)

Figure 2. A – A gross view of the excised breast lump. Note the external surface appears smooth with the cut surface showing a greenish tinge (scale bar = 4 cm); B, C and D show sections from the breast mass, which reveal tumor cells composed of monomorphic population of cells, predominantly composed of blasts along with few scattered mature and immature granulocytes. Normal breast parenchyma is seen at the periphery in B, indicating that the tumor was circumscribed (H&E, B-100x; C - 200x; D - 400X).

Figure 3. - Immunohistochemical profile of the breast lump - The tumor cells are strongly reactive for A – LCA; B – TdT highlights the myeloblasts; C – The tumor cells also react diffusely to CD43; D – CD68 (diffuse reactivity); E – CD117 (intermediate to weak reactivity); and F – CD99 (diffuse reactivity) (A to F, 400X).

Figure 4. A – Photomicrograph of the lymph node showing the replacement of lymph node parenchyma with sheets of blasts (H&E, 400x); B – Bone marrow aspirate showing numerous blasts (arrows) along with other cells of myeloid lineage, indicating blast crises of CML (Leishman’s stain,1000x); C-F – Immunohistochemical profile of the lymph node reveals the blasts being diffusely positive for: C - CD34; D – MPO; E - focal reactivity to CD117; and F - non-reactivity to ALK1 - (C to F, 400x).

Figure 5. A – Peripheral blood smear showing an abnormal promyelocyte composed of an eccentric folded nucleus with nucleolus and abundant cytoplasm showing numerous granules along with the presence of Auer rods (arrow) (Leishman's stain, 1000x); B – Bone marrow aspirate shows promyelocytes (arrows) along with a few blasts and myeloid precursors (Leishman's stain, 1000x)

Figure 6. May Grunwald - Giemsa (MGG) stained smears from the FNAC of temporal swelling reveal a monomorphous population of cells composed of intermediate-sized cells with pinkish granular cytoplasm and prominent nucleoli (arrows), suggesting overall features to be of a hematolymphoid malignancy in a known case of APML (400x).

Figure 7. A – Peripheral blood smear showing the presence of myeloid blasts (Leishman stain,1000x); B – Bone marrow aspirate reveals presence blasts (arrows) with cells of myeloid lineage (Leishman stain, 1000x).

Figure 8. Photomicrographs of the cervical mass: A – shows scant endocervical glands along with stroma being infiltrated by atypical monomorphic cells in sheets (H&E, 400x); B-D – Immunohistochemical reactions reveal the atypical cells showing strong reactivity to: B - LCA, C – MPO, and D – CD117, indicating their myeloid lineage (400x).