The challenge of dermatopathological diagnosis of composite tissue allograft rejection: a review

Advances in immunosuppressive treatments and microsurgical techniques have rendered allotransplantation of composite tissues (i.e. heterogeneous, non-organ tissues) possible in humans. Most of these allografts (hands, face and abdominal wall) contain skin that may be the target of rejection, the diagnosis of which relies mainly on clinicopathological monitoring of the skin. Rejection of allografted skin manifests with changes that are characteristic but not very specific. Although composite tissue allografts are still in their infancy, they have opened a new era in the field of transplantation surgery and pathology, so that (dermato) pathologists may occasionally be faced with the challenge of diagnosing skin rejection of a composite tissue allograft. The diagnostic difficulties that may be encountered in the pathological evaluation of skin in this setting are discussed in this review.