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WHO Classification of Tumours
Monomorphic PTLD (B- and T/NK-cell types)
Tumours of haematopoietic and lymphoid tissues


Definition

The group of monomorphic (M) PTLD fulfill the criteria for one of the B-cell or T/NK-cell neoplasms that are recognized in the immunocompetent host and described elsewhere in this monograph. The only exception to this is that the small B-cell lymphoid neoplasms such as follicular lymphoma or MALT lymphomas are not designated as PTLD even though attention has been drawn to the occurrence of MALT lymphomas arising in the post-transplant setting
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Hsi ED, Singleton TP, Swinnen L, Dunphy CH, Alkan S (2000)
Mucosa-associated lymphoid tissue-type lymphomas occurring in post-transplantation patients.
Am J Surg Pathol 24: 100-6



. The M-PTLD should be designated as PTLD in the diagnostic line of the pathology report, and then further categorized based on the classification of lymphomas arising in the immuno­competent host. Although the term M-PTLD reflects the fact that most cases are composed of a monotonous proliferation of transformed lymphoid cells or plasmacytic cells, there may be significant pleomorphism and variability of cell size within a given case. In addition, because polymorphic and mono­morphic PTLD of B-cell origin form a spectrum, their distinction can become blurred. Currently, their distinction in problematic cases is usually based on a subjective assessment of whether there is a predominance of large transformed cells/immunoblasts. The presence of abnormalities in oncogenes and tumour suppressor genes may also favour the diagnosis of M-PTLD
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Knowles DM, Cesarman E, Chadburn A, Frizzera G, Chen J, Rose EA, Michler RE (1995)
Correlative morphologic and molecular genetic analysis demonstrates three distinct categories of posttransplantation lymphoproliferative disorders.
Blood 85: 552-65



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> Further categorization of M-PTLD:
Monomorphic B-cell PTLD
Monomorphic T/NK-cell PTLD

> Related Topics
Introduction: Post-transplant lymphoproliferative disorders (PTLD)
Introduction: Classification of lymphoid neoplasms