Peripheral blood T lymphocytosis in thymoma: an insight into immunobiology
Shruti Mishra1, Somanath Padhi2, Amit Kumar Adhya1
1Department of Pathology and Laboratory Medicine, All India Institute of Medical Sciences, Bhubaneswar, Odisha, 751019, India.
Purpose:
Peripheral blood T lymphocytosis (PBTL) is a rare, yet poorly understood manifestations of thymoma, which is postulated to be linked with autoimmune/paraneoplastic manifestations such as myasthenia gravis (MG), pure red cell aplasia (PRCA), etc.; more commonly encountered in this neoplasm.
Method:
We aim to describe the flowcytometric immunophenotypic data of PBTL in a 43-year-old male; 6 months after successful completion of chemoradiotherapy (CT/RT) for a large, invasive, and metastatic type B1 thymoma; and present a comprehensive review of all such cases reported over last 42 years (N = 21) (1977-2019).
Result:
A larger size of the tumors (≥ 10 cm), presence of local invasion and/or distant metastasis, and type B (cortical or lymphocyte rich) histology were more likely to be associated with PBTL. Tumors associated with MG/PRCA (N = 9/21) tend to have lower PBTL compared to those without such manifestations; and PBTL subsided following thymectomy with or without CT/RT. Immunophenotypic analysis of PB revealed a CD8 + > CD4 + mature (naïve) polyclonal T cells resembling late cortical thymocytes.
Conclusion:
Thymic intratumoral microenvironment might influence occurrence PBTL that may have a pathophysiologic link to development of autoimmune manifestations. Immunophenotypic characteristics of peripheral blood lymphoid cells should be the clue for accurate characterization and to avoid a misdiagnosis of a lymphoproliferative neoplasm.
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