Imaging Review of Skeletal Tumors of the Pelvis—Part I: Benign Tumors of the Pelvis

Abstract

The osseous pelvis is a well-recognized site of origin of numerous primary and secondary musculoskeletal tumors. The radiologic evaluation of a pelvic lesion often begins with the plain film and proceeds to computed tomography (CT), or magnetic resonance imaging (MRI) and possibly biopsy. Each of these modalities, with inherent advantages and disadvantages, has a role in the workup of pelvic osseous masses. Clinical history and imaging characteristics can significantly narrow the broad differential diagnosis for osseous pelvic lesions. The purpose of this review is to familiarize the radiologist with the presentation and appearance of some of the common benign neoplasms of the osseous pelvis and share our experience and approach in diagnosing these lesions.

Cytomorphology of Recurrent Osseous Extracranial Meningioma of Right Pubic Ramus:

“…Possible tumor‐like lesions include hemophilic pseudotumor, chronic osteomyelitis, and particle disease in postarthroplasty cases . Benign tumors that appear plausible include giant cell tumor, fibrous dysplasia, and aneurysmal bone cyst . Metastases from lung, breast, kidney, and prostate (in males) carcinoma involving pelvis are much more common than its primary malignancies.…”

Hip and Pelvis Bone Tumors: Can You Make It Simple?

“…13 Aneurysmal bone cysts do not have a specific predilection to the hip and pelvic region (7-9% in the proximal femur, 6% in the ilium, and 2% in the sacrum, pubis, and ischium). 1,4,[13][14][15][16][17][18][19][20][21][22][23][24][25] The imaging presentation is the same as elsewhere in the peripheral skeleton. The best diagnostic clue is the patient's age as well as the presence of an eccentric lytic lesion composed nearly entirely of fluid-fluid levels (notably, fluid-fluid levels are not pathognomic or obligatory; the neocortex can be extremely thin and hardly visible, and progression of this tumor can be very fast) (►Table 6).…”

“…MRI remains superior to CT in assessing the involvement of soft tissue and early periosteal reaction (unlike the outer fibrous layer, the inner cellular layer of the periosteum, the cambium, is only seen on MRI), the soft tissue components in adjacent joints, bone marrow, and the surrounding neurovascular structures, providing information during the initial diagnosis and for staging. 2,3,13,14 MRI is also more sensitive than CT for initial evaluation of the bone cortex (for instance, if there is permeation of a small round blue cell tumor in the cortex, there will be an increase in the cortical signal seen on MRI while CT is still normal).…”

“…4,5 Metastases and myeloma can be seen everywhere around the pelvis and the hip. 4,5,13,14 Always exclude metastasis first in the adult > 40 years of age, no matter where the lesion is in the pelvis. • The most common primary malignant osseous tumors of the pelvis are chondrosarcoma (CS) (28-24%), followed by Ewing's sarcoma (ES) (18-16%) and/or osteosarcoma (21-9%).…”

“…The femur is usually involved in the monostotic form (although not the bony pelvis, where it is uncommon to present as a monostotic lesion (< 2%); both the femur (90%) and/or pelvis (80%) are usually involved in the polyostotic form. 13,23 The imaging presentation is the same as elsewhere in the body. In the pelvis, typical fibrous dysplasia presents as lesions that are lytic and particularly occur in the iliac bones, even though the matrix is usually variable (lucent to sclerotic).…”