T prolymphocytic leukaemia
An uncommon disorder which often presents with a lymphocytosis with very high counts (frequently >100 x109/L), patients are often unwell at presentation (although slowly progressive forms also occur). There is frequently splenic enlargement, while lymphadenopathy, skin rashes and episcleritis may each be seen. Two rather different morphological types may be encountered. This refers to typical T-PLL
- Large or more often medium sized cells with agranular basophilic cytoplasm
- Cytoplasmic protuberances or blebs are frequent and free membrane vesicles may be seen
- Nucleus has a “mature” appearance with condensed chromatin and obvious nucleoli
- The cells closely resemble B-PLL (smaller size, irregularity and blebbing may help distinguish them)
Typical T-prolymphocytic leukaemia (T-PLL)
The film shows fairly typical appearances of T-PLL. Note that the cells are both large and numerous. In this case the appearances are quite variable with many large forms but also smaller cells (although in all cases larger than a normal lymphocyte). Cytoplasmic blebbing is seen in some cells, although is not as prominent as is often seen in the small cell variant. The largest examples look very "blast like" but the majority are less activated. All cells share similarities of appearance which reflects their clonal origin.
IMMUNOPHENOTYPIC RECOGNITION OF T-PLL cells
The immunophenotype is not fully distinctive, look for high CD7 with weak CD3, and for some cases for co-expression of CD4 and CD8.
OTHER CONFIRMATORY TESTS
Cytogenetic testing is frequently abnormal (though most often not distinctive). Some recurrent patterns may be observed:
- often complex karyotype involving chromosomes 8, 11, 14 and X.
- 70% have inv 14 or t(14;14). Less commonly seen is t(x:14)
Mutations affecting ATM, p53, BCOR and JAK3 are described and may have prognostic impact