Acute T lymphocytic leukemia with myeloid expression orMPAL dual phenotype?

According to MICM (cell morphology, immunology, cytogenetics, molecular biology) test results, most acute leukemias can be divided into acute myeloid leukemia (AML) or acute lymphocytic leukemia (ALL), but there are a few acute leukemias ( AL) malignant cells have no clear evidence that their antigen expression is differentiated along a single lineage.
This type of leukemia is called acute series of incomprehensible hemopathy (ALAL)
.

ALAL includes acute undifferentiated leukemia (AUL), which does not display lineage-specific antigens, and mixed phenotypic acute leukemia (MPAL)
.

MPAL also includes two types: different primitive cell populations expressing different antigenic lineages (dual series) and the same cell population expressing more than one lineage-specific antigen (dual phenotype)

The incidence of MPAL is low, <4% in acute leukemia
.

According to the immunophenotype, MPAL can be expressed as co-expression of B-lymphocyte and myeloid (B/My), co-expression of T-lymphatic and myeloid (T/My), and co-expression of B and T-lymphocytes (B/T).

Case history

Case process case process

A 74-year-old male patient was admitted to our hospital for the first time on October 25, 2021, mainly because of "acute leukemia diagnosed for 33 months and admitted to the hospital for chemotherapy"
.

In December 2018, he was diagnosed as "acute T lymphocytic leukemia with myeloid expression" by bone puncture in the local hospital in December 2018.

The patient's blood routine at the time of the initial onset: WBC 2.
7×109/L, NEU# 0.
83×109/L, Hb 125g/L, PLT 133×109/L
.

The bone marrow morphology suggests T-ALL

Blood routine when admitted to our hospital: WBC 8.
07×109/L, LYM# 7.
27×109/L, NEU# 0.
71×109/L, Hb 105g/L, PLT 54×109/L
.

Bone marrow aspiration was performed to assess the patient’s disease.

Cytochemical staining: POX: 99% (-), 1% (+), DCE: negative, PAS: about 10% of the cells are diffusely positive, ANAE: about 92% of the cells are diffuse to spot-positive, ANAE+ NaF: About 2% of the cells were diffusely positive, and the inhibition rate was 97.
8%
.

The result is shown in the figure below:

Multi-parameter flow cytometry showed that immature cells with abnormal immunophenotype accounted for 90.
23% of the total number of nuclear cells.
In addition to T-line characteristic antigens, this group of cells also expressed myeloid-related antigens: CD45dim+, CD34+, CyCD3+, CyMPOfew+ (positive rate 11.
88%) , CD7+, CD5dim+, CD33+, CD38+, CD11b+, CD99+, NuTdTpart+, CD117few+ (positive rate 13.
58%), HLA-DRfew+, CD71dim+, CD58+, CD81dim+, CD3-, CD2-, CD8-, CD1a-, CD4-, CD16- , CD56-, CD57-, CD13-, CD15-, CD64-, CD14-, CD66c-, CD19-, CD22-, CD20, -CyCD79a-, CD10-, CD138-
.

Conclusion: CD117/CyMPO/CyCD3 positive cells accounted for 11.
88% of the abnormal naive cells, which are T-line and myeloid phenotypes
.

The main flow chart is as follows:

Bone marrow biopsy results: in line with T-ALL, and immunohistochemistry shows that about 5-8% of tumor blasts express CD117 and MPO at the same time.
The histochemical diagrams of HE, CD3, CD117, and MPO are as follows:

Karyotype analysis showed normal karyotype
.

Molecular biology test: 51 fusion genes were tested negative, and mutations of NRAS, DNMT3A, IKZF1, PCLO and NOTCH1 were detected.

case analysis

Case study case study

The diagnosis of ALAL relies on immunophenotyping.
Flow cytometry is the first choice to confirm the diagnosis, especially when the co-expression of lymphoid and myeloid differentiation antigens is recognized on the same cell
.

In the identification of two (or more) different leukemia cell populations, bone marrow pathological immunohistochemical staining or smear cytochemical staining can be used in combination with flow cytometry

In this case, the bone marrow morphology was diagnosed as T-ALL at the time of the initial onset.
Flow immunophenotyping showed that the primordial cells express early differentiation antigen (CD34+), T-line antigen (CyCD3+, CD7+, CD5part+), and cross-line express myeloid antigen CD33part+
.

According to the results of morphology and flow cytometry, the T-ALL chemotherapy regimen was treated with poor efficacy, only achieving complete morphological remission, and flow cytometry MRD was always positive
.

After recurrence, he was transferred to our hospital, and the disease status was reassessed routinely, and the MICM + pathological examination was perfected
.
The bone marrow smear showed a typical morphology of lymphoid protomyocytes, and the relatively specific POX and DCE results in cytochemical staining were also consistent with the characteristics of lymphoid cells
.

Due to the routine detection of myeloid lineage, lymphoid lineage, and the characteristic antigens and intracellular antigens of each cell series in our hospital by flow immunophenotyping, it was found that the primordial cells not only expressed CD33, but also expressed myeloid antigens CyMPO and CD117.
The positive rate was 11.
88, respectively.
% And 13.
58%, in order to eliminate false positives caused during the experiment, a retest was carried out, and the positive rates of the two results were very close
.

The biopsy samples submitted at the same time also confirmed that about 5-8% of the tumor blasts in the bone marrow samples expressed both CD117 and MPO.
Based on the results of flow cytometry and pathology, the diagnosis of "T/My dual phenotype" can be considered
.

Experience

Experience and experience

The terms and definitions of ALAL, especially MPAL, have been somewhat ambiguous.
Before the publication of the WHO classification criteria, some acute leukemias reported to be biphenotypes should be classified as AML or ALL with cross-line antigen expression
.
The actual incidence of ALAL is less than reported.
The incidence of T/My is less than 1% of all leukemias, and it can occur in children and adults
.

The morphological characteristics of T/My primitive cells are similar to those of T-ALL.
The expressed T antigens usually include cCD3, CD7, CD5 and CD2, and generally do not express the surface antigen CD3.
In addition to expressing CyMPO, myeloid antigens often express other myeloid Departmental markers such as CD13, CD33 and CD117
.
Most T/My have clonal chromosomal abnormalities, but which abnormalities have not been found to be specific, and there is not enough literature to show which gene mutations are closely related to T/My
.

The flow cytometry phenotype of this case conforms to T/My, chromosome analysis shows normal karyotype, molecular detection of signal pathway gene NRAS and NOTCH1 mutations, IKZF1 mutations that are more common in ALL, epigenetic-related gene DNMT3A mutations, and in ALL There are occasional PCLO gene mutations detected.
After consulting the database, it was found that the mutation sites of the above five genes in this case have not been reported in leukemia, and the clinical significance is unknown
.

Studies have shown that the three genes IKZF1, NOTCH1 and DNMT3A have a higher frequency of mutations in T/My
.
It is generally believed that T/My has a poor prognosis.
Due to the small number of cases, there is no fixed treatment plan.
In the literature, various clinical teams have tried a single myeloid or lymphatic system, a myeloid + lymphatic system, and alternate lymphatic and myeloid systems.
Use, the result has not yet obtained consistency evaluation
.

Since the first diagnosis of this case, lymphatic chemotherapy has been used.
Although complete morphological remission has been achieved, flow MRD is always positive and the effect is not good
.
There is a view that using lymphatic regimen to induce allogeneic hematopoietic stem cell transplantation may be a better treatment strategy.
Unfortunately, this case is too old and has undergone multiple courses of chemotherapy.
In the end, the family chose to return to the local hospital
.

Although cytochemical staining can help to a certain extent, it is difficult to accurately distinguish biphenotypic MPAL leukemia cells based on cell morphology alone.
This case is a good example
.
At the morphological level, it cannot be distinguished from T-ALL, and finally relying on multi-parameter flow cytometry to make up for the lack of morphological typing
.

It is worth noting that when performing flow cytometry, when conditions permit, the selected antibody combination should cover each cell series as much as possible.
When there is cross-line expression, pay more attention to other characteristic antigens and cells in the corresponding cell series.
The expression of internal antigens
.

T/My needs to be differentiated from ETP-ALL (early precursor T lymphocytic leukemia), because the latter will also abnormally express myeloid and stem progenitor cell-related antigens such as CD13, CD33, CD117 and CD34, both of which can be passed CyMPO and CD1a, CD8, CD5 and other antigens are expressed or not and their strengths are distinguished
.
Although the diagnosis of MPAL mainly relies on flow cytometry, the analysis of MICM and pathological results can provide more accurate diagnosis and differential diagnosis, and provide an effective basis for prognostic judgment and individualized treatment plans
.

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