Myeloid Sarcoma of Lacrimal Gland: A Case Report

Myeloid sarcomas are rare complications of de novo AML [1]. The diagnosis of AML is based on finding greater than 30% myeloid blasts in the bone marrow. Myeloblasts have delicate nuclear chromatin, two to four nucleoli. The cytoplasm often contains fine, azurophilic, peroxidise positive granules often represented by auer rods. Evaluation of the peripheral smear is an invaluable tool in the diagnosis [2].

In AML, the immatureblast cells are released in the blood circulation, reaching distant extramedullary sites including the lacrimal gland. Accumulation of these leukemic cells in the soft tissues is termed as Myeloid Sarcoma [MS]. MS has been reported in 2.5 to 8% of patients with AML [3].

The occurrence of lacrimal gland myeloid sarcoma in children before the development of systemic leukemia, may frequently be confused with malignant tumors such as rhabdomyosarcoma, lymphoma and neuroblastoma. The accurate diagnosis of these cases can be challenging, particularly when there is no evidence of systemic disease and imaging featuresare not sufficiently specific to distinguish myeloid neoplasm from other tumors [4,5].

A 10-year-old male child came with complaints of protrusion of right eye and lid swelling for 1 month. Computed Tomography [CT] scan showed a well-defined, poorly marginated soft tissue mass involving the lacrimal gland, superior rectus and lateral rectus muscles of the right eye. Clinical diagnosis was an orbital pseudo tumour with a differential diagnosis of a lymphoma. The peripheral blood smear report was suggestive of an acute leukemia with the blast count of 40% (Figure 1). The bone marrow findings were suggestive of an acute leukemia of myeloid origin (Figure 2). Right sided lacrimal gland mass biopsy report revealed a myeloid sarcoma (Figure 3) confirmed by Myeloperoxidase [MPO] positivity (Figure 4).

Figure 1: Peripheral smear: Showing myeloblasts (arrow) with Auer rods. [Leishman’s stain: 1000x].

Figure 2: Bone marrow smear: Showing myeloblasts (arrow) with Auer rods. [ Leishman’s stain: 1000x].

Figure 3: Lacrimal gland biopsy: showing diffuse sheets of large blast cells resembling large cells infiltrating the lacrimal gland (acinar structures in 3a). [H&E: 40x].

Figure 4: Lacrimal gland biopsy: showing infiltrates of myeloblasts with diffuse MPO positivity. [MPO: 40x].

GS [Granulocytic Sarcoma] (also called chloroma) was first described by the British physician, Burns A in 1811 [6].The diagnosis of a GS can be difficult and sometimes it may be misdiagnosed. These tumors can occur anywhere in the body and they have to be differentiated from lymphomas, carcinomas or infectious process [7,8].

Due to the low incidence of myeloid (granulocytic) sarcoma, it is not possible to develop a proper algorithm for its diagnosis and treatment. Few descriptions that are available in the literature neither give an idea of the variety of manifestations and the order of organ involvement, nor allow any vital prognosis. Verification of the diagnosis can only be based on immunohistochemical findings of the primary tumor and bone marrow biopsy material [9].

In our case, the lacrimal gland architecture was effaced by infiltration of diffuse, monotonous population of immature myeloid or blast like cells, which on special stain turned out to be MPO positive. The bone marrow aspirates revealed proliferation of blast cells with Auer rods which were positive for myeloperoxidase stain. The peripheral blood smears also showed myeloblasts with Auer rods in the cytoplasm.

The overall histopathologic appearance, peripheral blood smears and bone marrow smear findings with MPO positivity, was consistent with the diagnosis of extramedullary acute myeloid leukemia in the form of mass involving lacrimal gland [myeloid sarcoma].

Myeloid sarcoma, although rare, should be considered as one of the differentials when a paediatric patient presents with proptosis or eyelid swelling.

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