Nowadays, parachordoma is considered within the same spectrum with mixed tumor and myoepithelioma.5
In general, it is a benign, slow-growing and painless soft-tissue mass; however, recurrence and metastasis have been reported.3–5
Based on the review by Jonathan Clabeaux, there is a slight male predilection in parachordoma and the age range is from 4 to 86 years with an average age of 34.4 years. The most common location is the extremities (78%), followed by the thorax, trunk, pelvis and nares.3
In our review of literature, our case is the second pelvic parachordoma.3,6
Besides, the symptoms of severe pain and difficulty in defecating are rarely reported. A limitation in our case is that there are no enhanced images on CT or MRI because of her poor renal function. But, combining our case and the review of literature, we can have a more extensive and complete concept about the radiological features of parachordoma, including CT, MRI and even sonography. However, the sonographic appearance of parachordoma is similar to those of many different solid pelvic tumors, and thereby is of low value in diagnosing parachordoma, but sonography may be helpful to survey whether the nearby organs are involved.
On CT, parachordoma is typically a well-defined, homogeneous or slightly heterogeneous soft-tissue tumor without calcification. There is no bony involvement or peripheral fat stranding. The tumor is diffusely enhanced.7,8
and bony destruction8,11
occasionally exist. On MRI, parachordoma is hypo- to iso-intense on T1WI and heterogeneously hyperintense on T2WI with diffuse enhancement.3,8,10
There is no intratumoral fat component or peripheral fat stranding although minimal soft tissue edema surrounding the lesions has been mentioned.3
The description of the sonographic appearance is mainly based on our study because there is no relevant information depicted in any other study in our review of literature. The mass on sonography is heterogeneously isoechogenic with posterior acoustic enhancement and a thin hyperechogenic pseudocapsule. Blood flow is not detected on color Doppler imaging.
In conclusion, it is obvious that making a correct diagnosis in a case of parachordoma chiefly on the basis of radiological studies is really challenging. However, when encountering a tumor with the abovementioned radiological appearance, we can include parachordoma in the list of differential diagnosis, even though the tumor is not in the extremities, the typical location. The management and prognosis of this benign entity, though some malignant cases exist, are quite different from other diseases with sometimes similar radiological pictures but higher malignant potential, such as chordoma, and some other types of soft-tissue sarcoma.