A 32-year-old Indian woman presents with a 2-week history of easy bruising, petechiae, and gum bleeding. Blood smear shows 85% blasts with Auer rods. Which is the most common site of extramedullary involvement in acute myeloid leukemia?
A. Skin and soft tissues
B. Gingival infiltration
C. Central nervous system (CNS)
D. Spleen and liver
Explanation
Extramedullary Involvement in AML
Key Point
Spleen and liver are the most common sites of extramedullary involvement in AML, occurring in 40–50% of cases at presentation. Hepatosplenomegaly is a frequent clinical finding and is part of the standard staging workup.
Frequency of Extramedullary Sites in AML
Table
Site
Frequency
Clinical Significance
Spleen and liver
40–50%
Most common; part of staging
Gingival infiltration
20–30% (especially AML-M5)
Monocytic differentiation
CNS involvement
5–10% (at diagnosis); 30% (at relapse)
Poor prognosis; requires prophylaxis
Skin (leukemia cutis)
3–5%
Myeloid sarcoma; monocytic subtypes
Bone
2–3%
Rare; may cause bone pain
Lymph nodes
5–10%
Less common than in ALL
High-YieldNEET PG
Gingival infiltration (gum hypertrophy, bleeding) is particularly common in monocytic AML (AML-M5) and is a clinical clue to the diagnosis. The presence of Auer rods on blood smear (as in this case) confirms AML and rules out ALL.
Myeloid Sarcoma (Granulocytic Sarcoma)
Definition: Extramedullary tumor of AML blasts, also called "chloroma" (greenish color due to myeloperoxidase)
Sites: Skin, bone, soft tissues, CNS, mediastinum
Frequency: 2–10% of AML cases at diagnosis; 20–30% at relapse
Prognosis: Indicates aggressive disease and higher relapse risk
Clinical Pearl
In this case, the patient has gum bleeding (gingival infiltration) and Auer rods (confirming AML). The most common overall site of extramedullary involvement is still the spleen/liver (hepatosplenomegaly), even though gingival involvement is prominent in monocytic subtypes.
Do not confuse "most common site of extramedullary involvement" with "most common type of extramedullary involvement." Hepatosplenomegaly is the most common finding overall, but gingival infiltration is the most characteristic of monocytic AML.
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