Contributed by Wen-Wei Chung, MD, PhD, Remigio M. Gregorio, MD.
Published on line in October 2000
A 43-year-old obese female with history of sleep apnea, gastroesophageal reflux, and depression, presented with a vague left hip discomfort and low back pain of several weeks' duration. The plain radiography and CT scan of pelvis showed an expansile osteolytic lesion, 5 x 6 x 2.2 cm, involving the left iliac wing close to the sacro-iliac joint. Differential diagnoses based on radiologic findings included giant cell tumor, aneurysmal bone cyst, and metastatic carcinoma. Past history of hysterectomy for uterine leiomyoma 13 year prior to current admission was elicited. Physical examination and extensive studies of the entire gastrointestinal tract did not reveal any positive findings. The chest CT scan showed no evidence of metastatic disease. The Tc99m scintigraphy of whole body bone confirmed a solitary lesion involving the left ilium with no evidence of any other lesions. She underwent a biopsy followed by a modified left internal hemipelvectomy. Broad-spectrum antibiotics and anticoagulants were given postoperatively. The wound healed well without signs of infection. She was discharged at the 7th postoperative day with home pain management and followed up by physical therapy and occupational therapy without further adjuvant treatment.
PLAIN RADIOGRAPHY OF THE PELVIS showed vertebra with normal anatomic alignment and mild degenerative changes in lumbar regions characterized by small marginal osteophytes. There were no compression fractures. There was a radiolucent defect, measured approximately 4.5 x 3.5 cm., in the medial aspect of the left ilium extends inferiorly to the adjacent sacro-iliac joints. The overlying cortex along the medial aspect of the pelvis appeared to be intact. The margin lateral to the osteolytic lesion was somewhat indistinct.
CT SCAN OF THE PELVIS showed an expansile cystic lesion, 5 x 6 x 2.2 cm, involving the left iliac wing near the sacro-iliac joint and above the sciatic notch (Figure 01). The tumor was relatively homogeneous. It had sharp sclerotic margins, was well bounded by cortical bone, and had no soft tissue extension. There was no lymphadenopathy in the pelvic region. The urinary bladder was normal. There were no findings in uterus or bilateral adnexa.
MRI OF THE PELVIS confirmed the lesion seen in CT scan. In addition, the tissue density of the iliac lesion is very similar to the adjacent iliacus and gluteus muscles (Figure 02). The sacro-iliac joint appeared to be intact and was free from the tumor involvement.
Tc99m SCINTIGRAPHY OF WHOLE BODY BONE showed an abnormal uptake at the left posterior ilium with an area of photopenia surrounded by an area of increased activity on the scintigraphy. The most likely etiology was a myeloma/plasmacytoma, however, an aggressive metastatic tumor was also considered. The rest of the axial skeleton was normal.
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