[Miriam]

Hello:
Let me try to explain my doubt. Sometimes it seems that the apostrofe is optional such as in the following example: The patient was sent to the Specialist Hospital (one could also say Specialist´s Hospital or
Hospital of Specialists).
Thank you,
Miriam
Some people read my request but no one answered it. Snif, Snif.

[Eric]

Tricky question.

'Specialist Hospital' specialist would be an adjective, therefore it wouldn't need an 's.

in these cases "Specialist´s Hospital or Hospital of Specialists" specialist is a noun and therefore could have an 's.

Hope that helps and sorry about the late reply.

eric