Spindle Cell Lipomas Arising at Atypical Locations.
OBJECTIVE
Spindle cell lipomas (SCLs) are benign lipomatous neoplasms that classically arise in the posterior neck, upper back, and shoulders of older male patients. We sought to characterize the occurrence of this entity at nonclassic sites.


METHODS
All cases of SCL arising at atypical sites were retrieved from our archives.


RESULTS
Of 439 total cases of SCL, 57 arose at atypical locations in 32 men and 25 women (age range, 27-79 years). The tumor sites included leg (n = 23), buttock/perineum/inguinal (n = 10), forearm (n = 9), finger (n = 9), foot (n = 2), toe (n = 2), hand (n = 1), and flank (n = 1). CD34 was positive staining in all cases tested (52/52), while desmin was negative in most tumors (48/50). Thirty-eight of 38 cases tested exhibited loss of Rb expression. No cases showed CPM/MDM2 amplification (0/48). No local recurrences have been reported (n = 39).


CONCLUSIONS
SCLs may arise in the trunk, lower extremities, and distal upper extremities. While most SCLs arising in classic sites occur in male patients, there is a relatively equal sex distribution in tumors at atypical sites. Pathologists should be aware that SCLs arise at atypical locations to avoid misclassification as other lipomatous neoplasms, including atypical lipomatous tumor.
From the Department of Pathology and Laboratory Medicine, Aga Khan University Hospital, Karachi, Pakistan.
Nasir
N
Ud Din
Department of Laboratory Medicine and Pathology.
Pingchuan
P
Zhang
Department of Laboratory Medicine and Pathology.
William R
WR
Sukov
Department of Laboratory Medicine and Pathology.
Christopher A
CA
Sattler
Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN.
Sarah M
SM
Jenkins
Department of Pathology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA.
Leona A
LA
Doyle
Department of Laboratory Medicine and Pathology.
Andrew L
AL
Folpe
Department of Laboratory Medicine and Pathology fritchie.karen@mayo.edu.
Karen J
KJ
Fritchie
D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D002081:Buttocks / Q000473:pathology*; D005260:Female; D005528:Foot / Q000473:pathology*; D005542:Forearm / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D007866:Leg / Q000473:pathology*; D008067:Lipoma / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D012983:Soft Tissue Neoplasms / Q000378:metabolism / Q000473:pathology*; D060726:Torso / Q000473:pathology*
D014408:Biomarkers, Tumor
Lipoma; MDM2; Rb; Spindle cell lipoma