Histopathologic characterization of Morel-Lavallée lesion: Report of 6 cases and review of the literature.

Morel-Lavallée lesions (MLLs) are trauma-induced soft tissue injuries that can clinically mimic neoplasms, yet the pathologic features have only been reported for four cases. To address this, a retrospective case search was conducted at our institution from 2015 to 2022, yielding six cases. The combined ten patients presented with a mean age of 46 years (range: 13-72 years) with an equal gender distribution. Half of these cases resulted from motor vehicle accidents, while the other half were sports-related or due to mechanical falls. The median interval from injury to presentation was 6 months (range: <1 month -17 years), and from injury to MLL diagnosis was 12 months (range: 1.5 months - 25 years). These lesions most frequently involved the thigh (5/10, 50 %), hip or buttock (4/10, 40 %), and less commonly the lower leg (1/10, 10 %). Clinically, the majority of cases (8/10, 80 %) presented as tender, palpable mass-like lesions, while the remainder (2/10, 20 %) presented in association with a cellulitic wound or fistula. Histologically, most cases exhibited fibroconnective tissue with reactive myofibroblasts, fat necrosis, and fibrin deposition (9/10, 90 %), as well as pseudocyst or cystic components (6/10, 60 %). All ten patients underwent surgical excision with complete resolution and no complications. Given the surgical management of these lesions and their potential morphologic overlap with benign and malignant neoplasms, further histopathological documentation is warranted to improve recognition and prevent misdiagnosis.