Definitions Granulocytic sarcoma: extra-medullary solid destructive mass composed of immature cells of the granulocytic series. Extra-medullary myeloid tumour : a comprehensive term which encompasses all forms of extra-medullary leukaemic infiltrate.
Granulocytic sarcoma can present before, concurrent or after the diagnosis of AML or other myeloproliferative disorder.
Common sites : skin, gum, lymph nodes , sub-periosteal bone structures (skull, para-nasal sinuses, sternum, ribs, vertebrae, pelvis, etc), but has been described in a variety of other organs.
Histopathology
The morphology is variable. If well differentiated, all stages of myeloid differentiation are seen,with easily recognizable granulocytic differentiation. If poorly differentiated, the majority of the cells are large with vesicular nuclei, conspicuous nucleoli while a minority of cells have reniform or lobed nuclei with slightly granular eosinophilic cytoplasm. If blastic, there is a monotonous population of medium-sized cells with inconspicuous nucleoli, a high mitotic index, scanty cytoplasm and no eosinophilic granules.
There is a diffuse pattern of infiltration. Dissection of collagen by strings of neoplastic cells is a common feature. In lymph nodes, granulocytic sarcoma may show para-cortical or sinuses infiltration or efface the architecture with a diffuse infiltrate.
Immunohistochemistry
|
lysozyme |
100% |
|
100% |
|
|
myeloperoxidase |
80%, 88% (14/16)1 |
|
86% (12/14)1 |
|
|
chloroacetate esterase |
85% |
|
85%, 94%(16/17)1 |
|
|
MAC 387 |
70% |
|
65% |
|
|
neutrophil elastase |
40% |
|
50% |
|
|
CD45RO (UCHL1) |
20% |
|
15% |
|
|
4% |
|
|
CD20 (L26) |
rare positivity described |
|
MB2 |
rare positivity described1 |
|
rare positivity described |
|
|
0% |
|
|
0% |
|
|
rare1 |
|
|
rare positivity described1 |
|
|
positivity described |
Note: the proportion of cells stained varies with tumour differentiation; blastic/poorly differentiated tumours may show focal staining only. Important caveat: a panel including chloroacetate esterase, myeloperoxidase, lysozyme, CD43, together with CD79a and CD3 is particularly useful to confirm the diagnosis and exclude NHL ( The positivity with CD45RO has lead to misdiagnoses as T cell NHL, but this is likely to be less of a problem as CD3 becomes the first line T cell marker)
Differential Diagnosis
The main differential is large cell non-Hodgkin's lymphoma
PNET
Prognosis:
Most patients presenting with granulocytic sarcoma will eventually develop AML. However, a proportion of patient, treated with appropriate chemotherapy at presentation, will not develop leukaemia.
References
Ackowledgement
The information on this page was prepared by Dr L P Menasce.
©SMUHT/PW Bishop