Thymic tissue in the skin: a clue to the diagnosis of the branchio-oculo-facial syndrome: report of two cases.

The branchio-oculo-facial (BOF) syndrome is a rare autosomal dominant disorder with a peculiar phenotype related to a combination of craniofacial abnormalities. Rare examples presenting with dermal thymic tissue have been described. We are reporting 2 children, 15 and 4 months old, respectively, with BOF syndrome in whom surgical repair/excision of skin cervical lesions showed thymic tissue. In the first patient the thymic tissue was exposed to the surface, without epithelial coverage and contained areas suggestive of all stages of thymus formation. A dermohypodermal nodule of fully developed thymic tissue superficially covered by nonkeratinizing squamous epithelium was found in the second patient. Since pharyngeal pouches are not exposed to the surface during normal embryogenesis and the thymus originates from the third pharyngeal pouch, both examples seem to indicate that in BOF syndrome there is a more complex malformation than simply ectopic thymus tissue. Thymic tissue at the skin appears to be unique for BOF syndrome and in a given case may provide the clue for the accurate diagnosis of the malformation complex.