A peripheral blood smear/bone marrow aspirate from a patient is shown above. Based on the morphological features, what is the most likely diagnosis?

Question

Accepted Answer

A. Acute Lymphoblastic Leukemia (ALL). ## Image Findings
*   **Dominance of immature cells (blasts):** The field is overwhelmingly populated by large, abnormal cells, indicating a blast crisis.
*   **High nuclear-to-cytoplasmic ratio:** The nuclei are large and occupy most of the cell volume, with scant cytoplasm.
*   **Basophilic cytoplasm:** The cytoplasm is typically blue/basophilic.
*   **Fine, dispersed chromatin:** The nuclear chromatin is open and delicate, characteristic of immature cells.
*   **Inconspicuous or small nucleoli:** While some cells may show small nucleoli, they are generally not as prominent or multiple as often seen in myeloblasts.
*   **Absence of Auer rods:** No rod-like cytoplasmic inclusions are visible, which would point towards myeloid lineage.
*   **Occasional tingible body macrophage:** A macrophage containing cellular debris (seen on the right) suggests high cellular turnover, common in acute leukemias.

## Diagnosis
**Key Point:** The presence of a monotonous population of immature lymphoid cells (lymphoblasts) with a high nuclear-to-cytoplasmic ratio, fine chromatin, and basophilic cytoplasm is characteristic of **Acute Lymphoblastic Leukemia (ALL)**.

Acute lymphoblastic leukemia is a malignant neoplasm of immature lymphoid cells (lymphoblasts) that proliferate in the bone marrow and often circulate in the peripheral blood. The morphological features seen in the image, particularly the high N:C ratio, fine chromatin, and lack of myeloid features like Auer rods or prominent granulation, strongly support a diagnosis of ALL.

## Clinical Relevance
**Clinical Pearl:** ALL is the most common cancer in children, accounting for approximately 75% of childhood leukemias. While less common in adults, it can occur at any age.

## High-Yield for NEET PG
**High-Yield:** Immunophenotyping is essential for subtyping ALL into B-ALL (most common, CD10, CD19, CD20 positive) and T-ALL (CD2, CD3, CD5, CD7 positive). Terminal deoxynucleotidyl transferase (TdT) is a nuclear enzyme positive in >95% of ALL cases, making it a highly sensitive marker for lymphoblasts.
**Key Point:** The presence of >20% blasts in the bone marrow or peripheral blood is diagnostic of acute leukemia.

## Common Traps
**Warning:** Differentiating ALL from AML without Auer rods (AML-M0, AML-M7) can be challenging morphologically and requires immunophenotyping or cytogenetics for definitive diagnosis.

## Reference
[cite:Robbins Basic Pathology, 10th Ed, Ch 13, p. 598-600]

Answer

B. Multiple Myeloma

Answer

C. Chronic Lymphocytic Leukemia (CLL)

Answer

D. Acute Myeloid Leukemia (AML)

A peripheral blood smear/bone marrow aspirate from a patient is shown above. Based on the morphological features, what is the most likely diagnosis?

Explanation

Image Findings

Diagnosis

Differential Diagnosis

Clinical Relevance

High-Yield for NEET PG

Common Traps

Reference

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Feature	Acute Lymphoblastic Leukemia (ALL)	Acute Myeloid Leukemia (AML)	Chronic Lymphocytic Leukemia (CLL)	Multiple Myeloma
Cell Type	Lymphoblasts	Myeloblasts	Mature Lymphocytes	Plasma Cells
N:C Ratio	High	Variable, often lower than ALL, more cytoplasm	High	Variable, often moderate
Chromatin	Fine, dispersed	Fine, dispersed	Clumped, mature	Clumped, eccentric nucleus
Nucleoli	Inconspicuous/small	Often prominent, 1-2 or more	Inconspicuous	Often prominent
Cytoplasm	Scant, basophilic	Variable, often granular, may have Auer rods	Scant, basophilic	Abundant, basophilic, perinuclear halo (Golgi zone)
Auer Rods	Absent	Present in ~50% of cases (pathognomonic for myeloid)	Absent	Absent