Frequent expression of human leukocyte antigen class I and the status of intratumoral immune cells in alveolar soft part sarcoma

The prognosis of alveolar soft part sarcoma is poor, despite the slow growth of the tumor. A number of cases with spontaneous regression of this rare tumor have been reported. Although the mechanisms underlying spontaneous regression remain uncertain, local immune reaction may be a possible contributing factor. Immunohistochemical expression of human leukocyte antigen (HLA) class I, cluster of differentiation (CD) 3, CD4, CD8, CD20, CD45, CD56, CD68, CD138 and CD163 were assessed in a series of 10 alveolar soft part sarcomas, and the expression profiles were associated with patients' clinicopathological parameters. Expression of HLA class I was observed in almost all the tumor cells of all cases. CD8(+) cells were identified in all tumors with varying densities. Moderate infiltration of CD8(+) cells was detected in three patients; one of these patients survived with long-term tumor remission. Infiltration of CD10(+), CD20(+), CD56(+) or CD138(+) cells was not revealed in all tumors. Moderate-diffuse infiltration of CD163(+) cells was observed in all tumors. To the best of our knowledge, the present study represents the first report of intratumoral immune cells in alveolar soft part sarcoma. Frequent expression of HLA class I in tumor cells was observed. CD8(+) cells were identified at various densities and CD163(+) cells were observed in alveolar soft part sarcoma. Moderate infiltration of CD8(+) cells in patients with a good prognosis may indicate the antitumor effects of immune cells in alveolar soft part sarcoma.