Table 1.

Clinicopathologic Characteristics of Patients.

Patient	Age (years)/Sex	Clinical history	Imaging findings and impression	Operative procedure	Gross size (largest dimension)	MDM2 FISH	CDK4 FISH	Follow-up (months)
1	81/Female	Recurrent UTI; cystocele and diverticulum of urinary bladder	Not visualized on imaging, incidentally found perioperatively	Complete excision	3.4 cm	Neg	Neg	DOC
2	64/Female	Cirrhosis; PBC; Liver and kidney transplant; mass detected during imaging for other diseases	15.8 cm circumscribed, fat attenuation mass with internal septation in the right retroperitoneum with mild mass effect on the inferior pole of right kidney; liposarcoma	Complete excision after separation from Gerota's fascia	26 cm	Neg	Neg	ANER (129); followed by imaging for 92 months (for transplant), then clinically
3	36/Male	Self-visualized asymmetry of right lower abdominal wall	10 cm encapsulated and lobulated fat-containing mass filling the right lower quadrant extending to below the right kidney and reaching up to the anterior abdominal wall and iliopsoas musculature; lipoma	Complete excision of mass after separation from iliopsoas musculature	13.1 cm	Neg	Neg	ANER (20); followed by imaging
4	59/Male	Lumbar radiculopathy with incidental detection of “fatty” mass in abdomen	16 cm, minimally complex fat-containing lesion in the anteromedial aspect of left psoas muscle with lobulated, partially calcified focus along with the upper aspect; “atypical lipoma” versus WDLS	Complete excision after separation from musculature	16.5 cm	Neg	Neg	ANER (21); followed by imaging for 6 months, then clinically
5	44/Female	Abdominal bloating and back pain	20 cm mass in the left retroperitoneum, predominantly fatty with multiple septations and encasing the left kidney with mass effect; suspicious for well-differentiated liposarcoma	Conglomerate of tumors completely removed in piecemeal	41.2 cm; 2 additional resected portions—14 cm and 14.2 cm	Neg	Neg	ANER (20); followed clinically
6	52/Male	Sigmoid colon adenocarcinoma metastatic to lymph nodes, mass detected on surveillance imaging 4 years post-colectomy	12 cm, slowly growing retroperitoneal mass with variably thick encapsulation of up to 3 mm and suspicious solid component, displacing the left kidney anteriorly; lipoma with low suspicion for liposarcoma	Several separate tumors in the abdomen visualized perioperatively, incomplete removal for debulking	13.2 cm; separate pieces 10.8 cm in aggregate	Neg	Neg	ANER (16); followed by imaging
7	40/Female	Flank pain due to renal stones; mass discovered incidentally on imaging for renal stones, previous 2 c-sections, cholecystectomy (interval unknown)	16.7 cm mass in right lower pelvis with displacement of uterus and bladder to the left and superior displacement of the right ovary, suspicious for WDLS versus “atypical” lipoma	Complete excision	19.2 cm; smaller excised peritoneal nodule showed a benign multicystic mesothelioma	Neg	Neg	Recent surgery (6-month follow-up); ANER by imaging
8	70/Female	Recently diagnosed serous endometrial carcinoma, imaging revealed a large retroperitoneal mass.	14.6 cm fat-containing mass in the right pararenal space with enhancing solid component, suspicious for retroperitoneal liposarcoma	Partial resection	8.9 cm	Neg	Neg	Recent surgery (3 months follow-up)
9	68/Female	Right lower quadrant mass detected incidentally by PCP on physical examination; occasional nausea	15.8 cm mass within the lower abdomen and pelvis with several soft tissue septations; impinging on adjacent bowel; favored to be a low-grade liposarcoma	Partial resection	In multiple pieces, 15 cm in aggregate	Neg	Neg	ANER; presented after 15 months with ventral abdominal incisional hernia due to protrusion of residual lipoma; FISH for MDM2 amplification was negative in the reexcision. Imaging prior to reexcision did not show growth of residual tumor

Abbreviations: FISH, fluorescence in situ hybridization; UTI, urinary tract infection; DOC, died of other cause(s); PBC, primary biliary cirrhosis; ANER, alive and no evidence of recurrence; WDLS, well-differentiated liposarcoma; PCP, primary care physician.