Parosteal lipoma of the left zygomatic bone

Clinical History

Slowly enlarging, painful mass in the left cheek.

Imaging Findings

Slowly enlarging,painful mass in the left cheek.CT scan was performed in the axial plane using 3mm-thick slices.Findings included a well defined mass measuring 2,5x2 cm lateral to the left zygomatic bone,which presented internal homogeneously fatty density and linear calcification of its apparent capsule.The mass was adherent with a broad base to the underlying bone which presented a small but definite periosteal reaction.Patient underwent surgical resection of the tumor and pathologic report was "connective fatty tissue in continuum with tiny bony spicules, bounded by a pseudocapsule consisting of amorphus calcified collagen.

Discussion

Parosteal lipomas are rare benign tumors (0.3% of all lipomas) that appear to emerge from multidirectional mesenchymal modulation within the periosteum. Pathologically and cytogenetically are indistinct from usual lipomas . Comparative cytogenic tests have revealed common chromosomic alterations to both superficial and parosteal lipomas and more specifically a t(3;12)(q28;q14), giving support to a common histopathogenesis. The peculiarity of the parosteal lipoma lies in its clinical evolution which depends on its site of origin. It is in fact most often described in relation to the long bones of the limbs where it may lead to compression of neurovascular bundles or, as in this case, cause pain. The differential diagnosis should include the usual lipoma, which does not affect bone, a periosteal chondroma which contains no fat and presents characteristic calcification and a liposarcoma which presents mixed densities of fat and soft tissue and does not evoke periosteal reaction.

Differential Diagnosis List

Final Diagnosis

Parosteal lipoma of the zygoma.

URL:	https://eurorad.org/case/633
DOI:	10.1594/EURORAD/CASE.633
ISSN:	1563-4086