Mantle cell lymphoma
Caused by the chromosome translocation t(11;14) leading to overexpression of the cell cycle control protein cyclin D1. MCL frequently behaves in a clinically aggressive manner. Morphology can provide useful indications of this condition but will usually require additional confirmatory investigation.
- Generally, the abnormal lymphocytes have medium size, their most frequent defining feature being the variability of the morphological forms present
- Cytoplasm may be pale or basophilic, but is not usually extensive and there should be no hairy projections
- Nuclear appearance may vary between cells, but irregularity, indentation or complex appearance is frequently seen
- Nuclear chromatin tends not to be clumped (unlike CLL), but may vary from a primitive to a mature appearance, nucleoli may be evident
- Circulating number of abnormal cells varies and may be high, and neutropenia and thrombocytopenia may occur
Mantle cell lymphoma
There is no absolutely typical appearance of mantle cell lymphoma; this film shows the mixture of appearances that are frequently found. First, there are smear cells - not typical of MCL, but this film illustrates that they are not exclusive to CLL. Also, in this case the white cell count is clearly elevated (and platelets likely to be reduced). All the lymphocytes are abnormal, but the variability that characterises MCL is quite clearly shown. Some of the abnormal cells are small with condensed chromatin that resembles resting lymphocytes but with and irregular nuclear outline (which may be complex or indented). Note that the cytoplasm does not surround the erythrocytes. Accompanying these small cells are larger cells that have limited basophilic cytoplasm and more primitive appearance of their nuclear chromatin that almost resembles a blast cell. These larger cells also have nuclear irregularity but also have visible nucleoli. MCL is a very variable disease morphologically, and this film reveals some of the difficulties it can pose. Individual cells can resemble the small clefted appearance of follicular lymphoma or more complex nuclear forms seen in T-cell lymphomas such as Sézary syndrome. The larger cells may easily be diagnosed as blast cells. While diagnosis will need conformation, this spectrum of appearances should alert the morphologist that this is not CLL.
AUDIO COMMENTARY: The morphology of mantle cell lymphoma
IMMUNOPHENOTYPIC RECOGNITION OF MCL
The most common difficulty with MCL immunophenotype is to distinguish the condition from atypical CLL. Markers may be helpful (often together with bone marrow trephine biopsy or lymph node examination, and cytogenetic or genetic testing).