CD7+ stem cell leukemia/lymphoma. Features of a subgroup without circulating blast cells

Acute undifferentiated leukemia limited to neck lymph nodes and a large mediastinal mass

In the 2016 update of the World Health Organization (WHO) classification of myeloid neoplasms, acute undifferentiated leukemia (AUL) was defined by a lack of lineage-specific markers. AUL has very poor prognosis and no established therapies due to its rarity. We report a case of a 31-year-old man with AUL who showed complete molecular response to an acute lymphoblastic leukemia (ALL)-based regimen and received allogeneic hematopoietic stem cell transplantation. The patient's blast cells were CD7-positive and localized to lymph nodes in the neck and to a large mediastinal mass; there was also rearrangement of the T-cell receptor delta locus. Although the tumor showed characteristics of T-cell lymphoblastic lymphoma, it was categorized as AUL based on WHO classification. This case suggests that a high-intensity conditioning regimen could be effective for rare cases of AUL that present only in the extramedullary mass, and chemotherapy for AUL should be selected based on the characteristics of the blasts.

Aleukemic extramedullary T lymphoid/myeloid bilineage hematopoietic and lymphoid malignancy with progression to bilineage leukemia at relapse: A case report

Bilineage T lymphoid and myeloid (T/My) neoplasms are rare entities among the hematopoietic and lymphoid malignancies. The majority of patients present with leukemic symptoms in which blasts are observed in the peripheral blood (PB) or bone marrow (BM) at a percentage of >20% of nucleated cells. Only a minimal number of cases of T/My bilineage hematopoietic and lymphoid malignancy have been reported with extramedullary infiltration as the initial symptom. The origin of the neoplastic cells in T/My bilineage malignancy has been documented as the hematopoietic stem cells. The present study reports the case of a 31-year-old man with a T/My bilineage malignancy, which initially showed cervical lymph node enlargement beyond the diagnostic criteria of leukemia in the PB and in the BM. Two distinct malignant populations were detected in the cervical lymph node and pleural effusion, one of which was positive for MPO-staining, while the other was positive for cytoplasmic cluster of differentiation 3. Mutations in platelet-derived growth factor receptor α, platelet-derived growth factor receptor β, fibroblast growth factor receptor 1 and other chromosome abnormalities were excluded. The patient obtained complete remission after conventional chemotherapy, but relapsed with bilineage leukemia within a short period of time. Lymphoid and myeloid lineages have been reported to be differentiated from multipotent progenitors asymmetrically. However, the cellular mutation stage in T/My bilineage malignancy remains unclear. The present study also reviews the origin, development and therapeutic strategies for extramedullary T/My bilineage malignancy.

Non-B, Non-T Neoplasms With Lymphoblast Morphology

We studied the morphologic, immunohistochemical, and clinical characteristics of 158 cases of lymphoblastic lymphoma. Based on immunophenotyping and cell lineage, cases were classified into B-cell type (CD20,CD19 or CD79a+, n = 53), T-cell type (surface CD3+, n = 84), and non-B, non-T type (B cell marker- and surface CD3-, n = 21). The latter group was further divided based on immunohistochemistry into: 1) CD7+ stem cell lymphoma (CD7+SCL) [CD4-, CD7+, CD33+/-, CD56-], 2) blastic natural killer cell lymphoma (B-NKL) [CD4-, CD7+/-, CD33-, CD56+, CD123-], 3) myeloid/NK precursor cell leukemia (M/NKL) [CD4-, CD7+, CD33+, CD56+], and 4) CD4+CD56+ hematodermic malignancy (CD4+CD56+) type [CD4+, CD7+/-, CD33-, CD56+, CD123+]. The CD7+SCL and M/NKL types frequently exhibited bone marrow invasion and mediastinal masses. All CD4+CD56+ types were associated with skin lesions. B-NKL type is included into Blastic NK lymphoma in new World Health Organization classification with CD4+CD56+ type. But the cases of B-NKL were more reminiscent of CD7+SCL or M/NKL type than the CD4+CD56+ type, both clinically and histologically. We propose that blastic NK lymphoma, a disease entity in the new WHO classification, should be divided into two types based on phenotypes and clinical features. The non-B, non-T lymphomas exhibited poorer prognoses, similar to that of B-cell lymphomas, than T-cell type tumors (P = 0.009). Among the 21 tumors, the prognosis of the four subtypes did not differ significantly; however, cases receiving aggressive chemotherapy and stem cell transplantation had a more favorable prognosis than those receiving only traditional chemotherapy and radiation therapy (P = 0.0089).

CD7+ and CD56+ Myeloid/Natural Killer Cell Precursor Acute Leukemia: A Distinct Hematolymphoid Disease Entity

The disease spectrum of natural killer (NK) cell leukemias and lymphomas has recently been expanding with the continuing evolution in diagnostic concepts. We describe here seven cases of acute leukemia of conceivable myeloid and NK cell precursor phenotype in six men and one woman varying from 19 to 59 years of age (median, 46 years). Striking extramedullary involvement was evident at initial presentation, with peripheral lymphadenopathy and/or mediastinal masses. Two lacked any leukemic cells in the bone marrow at diagnosis. Using cytochemical myeloperoxidase staining, less than 3% of the leukemic cells showed positive reactivity. However, expression of CD7, CD33, CD34, CD56, and frequently HLA-DR, but not other NK, T-cell, and B-cell markers was observed. Cytoplasmic CD3 was detected in three of the cases by flow cytometry and in six by Northern blotting, suggesting an origin from common progenitors between the NK cell and myeloid lineages. All but one presented germline configurations of the T-cell receptor β and γ chain genes and Ig heavy chain gene. With regard to morphology, the cells were generally L2-shaped, with variation in cell size, round to moderately irregular nuclei and prominent nucleoli, pale cytoplasm, and a lack of azurophilic granules. Histopathologic examination of biopsied specimens of extramedullary tumors showed a lymphoblast-like morphology, implying the differential diagnostic problem from lymphoblastic lymphomas, especially in cases lacking bone marrow involvement. Three patients were successfully treated with chemotherapy for acute myeloid leukemia (AML), whereas three other patients proved refractory to chemotherapeutic regimens for lymphoid malignancies, although two responded to subsequent AML chemotherapy. However, despite intensive chemotherapy, including allogeneic bone marrow transplantation, most persued fatal courses within 41 months. These data suggested that the CD7+ and CD56+ myeloid/NK cell precursor acute leukemia might constitute a distinct biologic and clinical disease entity. Its recognition appears to be particularly important for the clinicopathologic evaluation of CD56+ hematolymphoid malignancies and the development of therapeutic approaches to such disease.

CD7+ and CD56+ Myeloid/Natural Killer Cell Precursor Acute Leukemia: A Distinct Hematolymphoid Disease Entity

The disease spectrum of natural killer (NK) cell leukemias and lymphomas has recently been expanding with the continuing evolution in diagnostic concepts. We describe here seven cases of acute leukemia of conceivable myeloid and NK cell precursor phenotype in six men and one woman varying from 19 to 59 years of age (median, 46 years). Striking extramedullary involvement was evident at initial presentation, with peripheral lymphadenopathy and/or mediastinal masses. Two lacked any leukemic cells in the bone marrow at diagnosis. Using cytochemical myeloperoxidase staining, less than 3% of the leukemic cells showed positive reactivity. However, expression of CD7, CD33, CD34, CD56, and frequently HLA-DR, but not other NK, T-cell, and B-cell markers was observed. Cytoplasmic CD3 was detected in three of the cases by flow cytometry and in six by Northern blotting, suggesting an origin from common progenitors between the NK cell and myeloid lineages. All but one presented germline configurations of the T-cell receptor β and γ chain genes and Ig heavy chain gene. With regard to morphology, the cells were generally L2-shaped, with variation in cell size, round to moderately irregular nuclei and prominent nucleoli, pale cytoplasm, and a lack of azurophilic granules. Histopathologic examination of biopsied specimens of extramedullary tumors showed a lymphoblast-like morphology, implying the differential diagnostic problem from lymphoblastic lymphomas, especially in cases lacking bone marrow involvement. Three patients were successfully treated with chemotherapy for acute myeloid leukemia (AML), whereas three other patients proved refractory to chemotherapeutic regimens for lymphoid malignancies, although two responded to subsequent AML chemotherapy. However, despite intensive chemotherapy, including allogeneic bone marrow transplantation, most persued fatal courses within 41 months. These data suggested that the CD7+ and CD56+ myeloid/NK cell precursor acute leukemia might constitute a distinct biologic and clinical disease entity. Its recognition appears to be particularly important for the clinicopathologic evaluation of CD56+ hematolymphoid malignancies and the development of therapeutic approaches to such disease.

Kinase domain of the muscle-specific receptor tyrosine kinase (MuSK) is sufficient for phosphorylation but not clustering of acetylcholine receptors: required role for the MuSK ectodomain?

Formation of the neuromuscular junction (NMJ) depends upon a nerve-derived protein, agrin, acting by means of a muscle-specific receptor tyrosine kinase, MuSK, as well as a required accessory receptor protein known as MASC. We report that MuSK does not merely play a structural role by demonstrating that MuSK kinase activity is required for inducing acetylcholine receptor (AChR) clustering. We also show that MuSK is necessary, and that MuSK kinase domain activation is sufficient, to mediate a key early event in NMJ formation-phosphorylation of the AChR. However, MuSK kinase domain activation and the resulting AChR phosphorylation are not sufficient for AChR clustering; thus we show that the MuSK ectodomain is also required. These results indicate that AChR phosphorylation is not the sole trigger of the clustering process. Moreover, our results suggest that, unlike the ectodomain of all other receptor tyrosine kinases, the MuSK ectodomain plays a required role in addition to simply mediating ligand binding and receptor dimerization, perhaps by helping to recruit NMJ components to a MuSK-based scaffold.

T-stem cell leukemia/lymphoma with both myeloid lineage conversion and T-specific delta recombination

We evaluated retrospectively the clinical and biological characteristics of six patients with CD7+ early T-acute lymphoblastic leukemia and lymphoma (T-ALL/LBL) originating from prothymocyte stage I (pro-T I) or II cells. Patients exhibited mediastinal mass (five of six) and lymphoadenopathy (five of six) but without leukocytosis and circulating blast cells (six of six). All patients achieved a complete remission. All but one had a relapse with a transformation to the mixed type (triphenotype--three cases, biphenotype-two cases) including myeloid features in three patients. The altered phenotypes were myeloperoxidase (MPO)+ (three of five), CD13+ (four of five), CD33+ (three of five) and CD19+ (three of five). The difference for MPO-positivity were observed between the bone marrow (BM)- and lymph node (LN)-blast cells (three of three). On cytogenetic analysis, there is no common abnormality in these patients. Immunomolecular analysis revealed T-cell lineage specific delta gene rearrangements [D delta 2-J delta 1 (five of six) and V delta 1-J delta 1 (one of six)] in all cases. Furthermore, D delta 2-J delta 1 occurred even in the cases with the pro-T I phenotype. Rearrangements of TCR beta, gamma or immunoglobulin heavy chain genes occurred in three patients. The same rearranged band(s) appeared at both diagnosis and relapse, indicating the same originality of the pro-T leukemic cell clone (three of three). We suggest that this type of CD7+ early T-ALL/LBL was transformed from a pro-T I or II cell, such as T-stem cell leukemia/lymphoma, which is a subtype of CD7+ stem cell leukemia as defined by Kurtzberg et al. This study reveals that pro-T I and II cells might be capable of myeloid, T- and B-lymphoid differentiation, and T-cell lineage specific TCR delta recombination occurs.

Occurrence of acute megakaryoblastic leukemia in a patient with idiopathic growth hormone deficiency

We describe a case of a 15 year old boy who developed acute megakaryoblastic leukemia (AMKL) while receiving treatment with human growth hormone (hGH) for idiopathic growth hormone deficiency (GHD). He was diagnosed as having idiopathic GHD and given hGH from December 1991. The examination of his peripheral blood showed mild pancytopenia 2 months before the start of the hGH therapy. Since January 1992, paleness of the skin, general fatigue and fervescence progressed gradually. In February 1992, because of the occurrence of acute leukemia, administration of hGH was discontinued. Judging from the results of surface marker analysis of the blast cells, the patient was diagnosed as having AMKL. He was treated with chemotherapy for acute non-lymphoblastic leukemia from March 1992. A complete remission was obtained after 4 weeks of treatment. The chemotherapy was completed in July 1993. He remains in complete remission 26 months after diagnosis. This case suggests the importance of hematological examination and, when there is any abnormality which is not caused by GHD, such as pancytopenia, more detailed medical examinations (for example bone marrow examination) are necessary.