Brown a tumour is seen in
Brown's tumour is seen in Hyperparathyroidism. 
It's an expansile lytic lesion. This is a collection of osteoclasts.
It commonly found in maxilla and mandible, other bones also affected.
Other features are multiple bone cysts, subperiosteal retraction of bones, salt and pepper appearance of the skull in X-ray.
Hypothyroidism
Hyperparathyroidism
none
all of the above