**5. Conclusions and recommendations**

Neonatal thymectomy have immunological consequences in short- and medium-time, despite these defects are not associated with clinical outcomes. T lymphocytes show a trend to normalization and stabilization in long-term analysis. Normalization could be due to thymic tissue regeneration. However, several features of exhaustion and senescence are detected in young adults 20 years old that underwent thymectomy in the first year of life. Premature immunosenescence is not found in age-matched nonthymectomized controls. In a reassuring way, despite the immune response to newly encountered antigens is delayed, clinical consequences (increased infection rates or other clinical signs of immune weakness) are not observed at any age. Subsequent studies are needed to determine the consequences, if any, of the thymectomy-induced premature senescence once chronological immunosenescence starts exhausting the immune system. On the other hand, elderly thymectomy data is still missing, but information showing that thymus still has relevance in seniors strongly suggest the need of caution before performing complete thymectomy: thymus removal in elderly individuals aggravates a previously frail immune system.

The topic remains controversial, and strong data are still scarce. Moreover, open heart surgery is an important procedure with priority over an immunosenescent scenario. However, our recommendation in children's surgery, where the great size of the thymus forces the surgeon to resect to gain unrestricted view of the operation site, is to proactively preserve the maximum possible tissue. During interventions of adult or elderly patients, which atrophied thymus is no longer a critical problem to reach the surgical field; our recommendation is to preserve the complete organ to guarantee the maximal integrity of the immune system.
