A patient presented with a rapidly growing mass in the cervicothoracic para
spinous region. Associated clinical and radiographic skeletal abnormalities
and histopathologic findings showing mild to moderate proliferation of spi
ndle cells in a myxoid stroma led to the diagnosis of fibrodysplasia ossifi
cans progressiva. Recognizing the clinical features of this dis ease is imp
ortant and should avoid the need for obtaining tissue to make the diagnosis
, because performing a biopsy may be particularly morbid in these patients.