# Molecular analysis of T-cell Acute Lymphoblastic Leukemia arising after Essential Thrombocythemia foreshadows a distinct clonal route for lymphoid blast crisis in Philadelphia-negative chronic myeloproliferative neoplasm: a case report with literary review

## TL;DR

This case study explores a rare progression from Essential Thrombocythemia to T-cell Acute Lymphoblastic Leukemia, suggesting a new clonal pathway for lymphoid blast crisis in chronic myeloproliferative neoplasms.

## Contribution

The study provides molecular evidence supporting a distinct clonal origin for secondary Acute Lymphoblastic Leukemia in Philadelphia-negative chronic myeloproliferative neoplasms.

## Key findings

- Molecular analysis supports a different clonal route for lymphoid blast crisis in Philadelphia-negative chronic myeloproliferative neoplasms.
- Secondary Acute Lymphoblastic Leukemia should be viewed as a separate cancer rather than a true blast crisis.
- A review of published cases highlights the rarity and unique features of MPN transforming to Acute Lymphoblastic Leukemia.

## Abstract

Progression to Acute Myeloid Leukemia is a well-known complication of classical philadelphia-negative chronic myeloproliferative neoplasms, while disease progression to Acute Lymphoblastic Leukemia remains an extremely unfrequent event. A molecular explanation for this rare phenomenon is missing. However, the clonal haematopoiesis mostly present in these patients may work as a seeding soil for a second neoplastic disease. Molecular results from this case study reporting a secondary Acute Lymphoblastic Leukemia presenting after Essential Thrombocythemia support this hypothesis. In this contest secondary Acute Lymphoblastic Leukemia should not be considered as real blast crisis, but rather as a second cancer determined by a different clonal route. Given the unique features of this case, a review of the published cases of MPN transforming to Acute Lymphoblastic Leukemia available in literature is provided in the article.

The online version contains supplementary material available at 10.1007/s00277-025-06404-z.