Allogeneic stem cell transplantation (also termed "bone marrow transplantation") involves transferring stem cells from a healthy person (the donor) to the patient, after high-intensity chemotherapy or radiation, given to destroy any remaining cancer cells in the body. When a transplant is successful, the donor stem cells replace the original cells in the bone marrow. It may provide the only long-term cure of the patient's disease. Of transplant-related complications, graft-versus-host disease (GVHD) is one of the most important complications. GVHD arises from donor immune cells, that identify the recipient's (the patien's) cells as foreign and attack them. Approximately half of women undergoing transplantation will experience GVHD involving the genitalia (i.e., the vulva and vagina), termed vulvovaginal GVHD (VV-GVHD). VV-GVHD may cause irreversible anatomical changes, including complete vaginal obliteration, and not surprisingly, it has a severe impact on patients' quality of life and sexual function. This complication is unpredictable and non-preventable by the usual immunosuppressive treatment given to patients. Frequent gynecological examinations and prolonged follow-up of transplanted women are needed, to allow early diagnosis and prevention of harmful results of VV-GVHD. This follow-up adds inconvenience and anxiety to the patients.

The suggested study aims to evaluate a possible association between vaginal microorganisms (the "microbiome") to the progress of VV-GVHD. Finding such association may allow prediction of VV-GVHD progress, a better understanding of the development of VV-GVHD and a potential to develop interventions for the treatment and prevention of VV-GVHD.

Inclusion Criteria:

• Age≥18
• Candidate for allogeneic stem cell transplantation
• Ability to sign an informed consent

Exclusion Criteria:

- Patient does not approve sample collection

Female patients planned for HSCT