Background: Fibrolamellar hepatocellular carcinoma (FLHCC) is a rare variant of hepatocellular carcinoma (HCC) with about 200 annual cases reported globally. Surgical resection is the main treatment. Although FLHCC develops in the absence of cirrhosis surrounding hepatic parenchyma may have mononuclear cell and lymphocyte infiltrates. Immunotherapy by targeting programmed death 1 (PD-1) has emerged as a potential therapy for HCC and multiple clinical trials are being conducted, however little is known about immunological features of FLHCC. We aimed to analyze tumor microenvironment by immunohistochemistry and flow cytometry. Methods: Surgical samples of two FLHCC cases, 23 year old woman (case 1) and 25 year old man (case 2) who underwent neoadjuvant chemotherapy with 5 Fluorouracil + Interferon followed by surgical resection were analyzed. Expression of CD4, CD8, PD-1, programmed death ligand 1(PD-L1), CD45RO, CD 57, CD68, OX 40, inducible costimulator (ICOS), FoxP3, Gr-B was evaluated by immunohistochemistry. Flow cytometry analysis of CD8, CD4 effector (Teff) and regulatory (Treg) T cells were performed. Immune monitoring studies were conducted by the Immunotherapy Platform at MD Anderson Cancer Center. Results: By immunohistochemistry,expression of PD-1 and PDL-1 in the tumor sampleswas asfollows:PD-1 (5.9%) and PDL-1 (4.1%) of total cells in case 1 versus PD-1 (6.3%) and PDL-1 (3.5%) in case 2. FoxP3 expression was 0.3% and 1%, whereas ICOS expression was 0.2% and 1% in case 1 and 2, respectively. By flow cytometry analysis, case 1 presented the following frequencies: CD8+CTLA4+ (40%), CD8+PD1+ (40%) of total CD8 T cells, CD4+TeffCTLA4+ (55%), CD4+TeffPD1+ (30%), CD4+TeffICOS+ (15%) of total CD4 Teff cells and CD4+TregCTLA+ (90%), CD4+TregPD1+ (30%), CD4+TregICOS+ (70%) of total CD4 Tregs. Similarly, in case 2 the percentages were CD8+CTLA-4+ (20%), CD8+PD1+ (40%), CD4+TeffCTLA4+ (25%), CD4+TeffPD1+ (65%), CD4+TeffICOS+ (30%), CD4+TregCTLA+ (90%), CD4+TregPD1+ (70%), CD4+TregICOS+ (80%). Conclusions: PD-1, PDL-1, CTLA-4 and ICOS expression in FLHCC might render support to consideration of potential utilization of antibodies against PD-1, PDL-1 and CTLA-4 for treatment for a devastating cancer with unmet need for treatment.