[Clinicopathological features and prognosis of the skeletal-muscle cytotoxic T-cell lymphoma].

Objective: To investigate the clinicopathological features and prognosis of skeletal-muscle cytotoxic T-cell lymphoma (CTL). Methods: The clinical data of 14 cases of skeletal muscle CTL and 47 cases of non-skeletal muscle extranodal CTL patients in Beijing Friendship Hospital Affiliated to Capital Medical University and the 989 Hospital of the joint logistics support force of the people's Liberation Army (the former 152 hospital) from 2008 to 2019 were collected retrospectively. Immunophenotype, EBV infection status and T-cell receptor (TCR) clonality of tumor cells were evaluated. The clinicopathological features and prognosis of the two groups were compared. Results: Skeletal-muscle CTL accounted for 23.0% (14/61) of extranodal CTL in the same period. The median age of the patients was 42.3 years (range 11-76 years), including six males and eight females. The main clinical manifestations were painless masses. Two patients (2/14) had B symptoms. The tumors occurred in the cheek (7 cases), the tongue (4 cases), the lower lip (3 cases) and the left upper arm (2 cases), and in two cases had two sites. Ten cases were of stage ⅠE and four cases stage ⅡE. Compared with non-skeletal-muscle extranodal CTL, many patients of skeletal-muscle CTL did not have B symptoms, the clinical stage was lower, and the tumor mainly involved the oral cavity (cheek, tongue and lip, P<0.05). Morphologically, the tumor showed diffuse infiltration of heterotypic lymphocytes in skeletal muscle. Immunohistochemistry showed that in 11/14 cases, there were reduced or loss of expression of some the T cell antigens (CD2, CD3, CD5, CD7). TIA-1, Gr B and CD8 (CD8+>CD4+) were expressed in all cases, and CD56 was negative. The median Ki-67 proliferation index was 35.0% (range 5%-60%). EBER in situ hybridization was negative in all cases. The results of TCR clonality analysis showed clonal TCR gene rearrangement were detected in eight cases. The median follow-up time was 40 months (range 10-67 months). Ten patients were tumor free; the 5-year survival rate of skeletal-muscle CTL was 100%. Compared with non-skeletal-muscle extranodal CTL (5-year overall survival rate was 35.9%), the difference was statistically significant (χ²=8.277, P=0.004). Conclusions: Skeletal-muscle CTL mostly occurs in the skeletal muscle of cheek and mouth. Tumor cells show morphologic characteristics of muscle invasion and myositis-like feature. It also shows CD8+>CD4+immunophenotype, cytotoxic molecular pattern and is associated with low clinical stage and good prognosis.