Pathology

A. left upper lobe orifice : Diffuse infiltration of monotonous small round cells with LCA positivity, compatible with myoblastic leukemia infiltration.  B. left upper lobe apical segment : Diffuse infiltration of monotonous small round cells with LCA positivity, compatible with myoblastic leukemia infiltration.

Brief Discussion
Chloroma, extramedullary myeloblastoma

green color by myeloperoxidase(King 1853)

AML > CML (5:1), 2.5%-9% of AML

~5% of adults ;  ~13% of children

other myeloproliferative disorder

myelofibrosis, hypereosinophilic syndrome, polycythemia vera

Presenting sign of myelogenous leukemia(35%)

No prognostic significance in AML

Negative prognosis in CML or myelproliferative disorder -> acute transformation

Location

can arise anywhere

CNS, head and neck, abdomen, pelvis, skin, subcutaneous tissue

predilection for subperiosteal and perineural

Via trans-haversian canal migration of leukemia cells from the bone marrow to periosteum

Capillary migration, perineural or perivascular

Intrathoracic granulocytic sarcoma, rare

Intrathoracic granulocytic sarcoma

mediastinum 50%

pleural effusion 22% mass 16%

cardiac tumor or pericardial effusion 20%

lung 18%        

hilum 16%; airway 8%

Diagnosis

Histopathology, leukemic cells in blood or BM

Radiographic monitoring

before CTx, during remission

response to CTx or RTx 4~12weeks

Exclusion of bleeding or infection

Imaging

Mediastinal widening

Lymphadenopathy, diffuse infiltration

Pleural disease

effusion, small nodule, extrapleural fat infiltration

Cardiac enlargement

cardiac tumor, pericardial effusion

Lung opacities

Alveolar, nodular, interstitial

Hilar enlargement

MR: isointense with involved bone marrow

Treatment

CTx, RTx or concurrent CTx and RTx

Sensitive but 23% of patients recur

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