Persistent non-neoplastic gammadelta-T cells in cerebrospinal fluid of a patient with hepatosplenic (gammadelta) T cell lymphoma: a case report with 6 years of flow cytometry follow-up.

Hepatosplenic (gammadelta) T-cell lymphoma (HSTCL) is an uncommon T-cell lymphoma with an aggressive clinical course and poor prognosis. Bone marrow and peripheral blood are frequently involved, with central nervous system involvement less common. We describe a case of a 31-year old man diagnosed with a gammadelta HSTCL in 2003, successfully treated with chemotherapy and allogeneic stem cell transplantation, and followed from 2003 to present. Four-color flow cytometry (FC) was performed on a BD FACSCalibur and data analyzed with CellQuest Pro and FCS Express software. For cerebrospinal fluid (CSF), all cells were acquired due to limited material. Cytological correlation was available on all specimens. Molecular studies for T-cell gene rearrangement were non-contributory. By FC, the diagnostic HSTCL immunophenotype was CD3 (+), CD7 (+), CD2 (+), CD5 (-), CD4 (-), CD8 (-), TCR gammadelta (+). Subsequent CSF FC analysis revealed a distinct population of gammadelta T-cells in all specimens, ranging from <1% to 13% of lymphocytes. Consistently, the gammadelta T-cells exhibited a different immunophenotypic profile from the reported diagnostic immunophenotype; they expressed CD5, and exhibited a heterogeneous pattern of CD8 expression. Comparison to in-house cases from patients with hairy cell leukemia and concomitant increases in non-neoplastic gammadelta T-cells was performed. The persistent gammadelta T-cells from the CSF of the patient with HSTCL were immunophenotypically consistent with non-neoplastic gammadelta T-cells. We describe an unusual case of persistent gammadelta T-cells in the CSF of a patient during 6 years of flow cytometric follow-up after treatment for gammadelta HSTCL. By cytology, non-neoplastic and malignant gammadelta T-cells are often difficult to distinguish. FC analysis helps to make this distinction, even with a limited panel. By FC, the gammadelta-T cells in the CSF of this patient are immunophenotypically consistent with non-neoplastic gammadelta T-cells. Remarkably, this finding is underscored by the patient's unusual clinical picture; he remains well and disease free.