[Clinicopathological features of T-lymphoblastic lymphoma with Langerhans cell histiocytosis in the same lymph node]

Objective: To investigate the clinicopathological features, immunophenotypes, genetics and prognosis of T-lymphocyte lymphoma/myeloid sarcoma combined with Langerhans cell histiocytyosis (coexistence of T-LBL/MS and LCH). Methods: Clinical and pathological data of the 6 patients with coexistence of T-LBL/MS and LCH were analyzed, who were diagnosed at the Foshan Hospital of Sun Yat-sen University and the Friendship Hospital of Capital Medical University, from December 2013 to April 2019. The hematoxylin and eosin stain, immunohitochemistry (EnVision) and in situ hybridization were used. Related literatures were reviewed. Results: Four patients were T-LBL combined with LCH, 1 was T-LBL/MS combined with LCH, and 1 was MS combined with LCH. There were 2 male and 4 female patients, with age ranged from 5 to 77 years old (median, 59 years old). Three patients represented with only multiple lymph node swelling. The other 3 displayed both multiple lymph node swelling, and skin/liver or spleen lesions. Lymph node structure was destroyed in 5 cases, while 3 cases had several residual atrophic follicles. Histologically, there were two types of tumor cells: one type of the abnormal lymphoid-cells exhibited small to medium-sized blast cells, typically showing a nested distribution, and these cells were mainly identified in residual follicles and paracortical areas; the other type of histiocytoid cells had a large cell size and abundant pale or dichromatic cytoplasm. Their nuclei were irregularly shaped, showing folded appearance and nuclear grooves. These cells were mainly present in marginal sinus, medullary sinus and interstitial area between follicles. Eosinophil infiltration in the background was not evident in any of the cases. The lymphoid-cells of medium size showed TdT+/CD99+/CD7+, with variable expression of CD34/MPO/CD2/CD3. Ki-67 index was mostly 30%-50%. However, the histiocytoid cells showed phenotype of CD1a+/S-100+/Langerin+/-, while CD163/CD68 were positive in some degree. These cells did not express any T or B cell markers. The Ki-67 index mostly ranged between 10%-20%. None of the cases had Epstin-Barr viral infection. Among the 6 patients, 4 patients were followed up (6-63 months, median time, 18.5 months), of whom 1 patient died of the disease and 3 patients were alive at the end of follow-up. Conclusions: T-LBL/MS combined with LCH is a rare mixed type of immature hematopoietic disease, and mainly occurs in lymph node and skin. The clinical course is overall aggressive. Therefore, it is helpful to recognize and identify the two pathologic components in the same tissue for accurate diagnosis and proper treatment.