Unusual association of CD8+ T-cell lymphocytosis with invasive thymoma

Thymolipoma associated with lymphocytosis in a 6-year-old girl: A case report

Thymolipoma is a benign and rare tumor that could be found at any age. Thymolipoma associated with the myasthenia gravis, Graves disease, aplastic anemia, and hypogammaglobulinemia was reported previously, but in this case, thymolipoma is associated with lymphocytosis. A 6-year-old girl was brought to the hospital because of a chronic cough. Her evaluation revealed a 130 × 160× 160 mm fat-containing soft tissue mass arising from anterior mediastinum with complete left lung collapse and contralateral mediastinal shift. Her past medical history showed that she had been evaluated and treated unsuccessfully due to severe lymphocytosis two years earlier. Her peripheral blood and bone marrow cell morphology were normal; in contrast, blood cell count and CD flow cytometry showed severe lymphocytosis. The patient's tumor was excised entirely without any complications, and lymphocytosis resolved during the follow-up period. Because the T lymphocytes are developed in the thymus, and more than 80% of cells in CD flow cytometry were T lymphocytes, and the lymphocytosis resolved with tumor removal; therefore, the authors suggested that Thymolipoma could be associated with lymphocytosis.

Peripheral blood T lymphocytosis in thymoma: an insight into immunobiology

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.