Xanthomatous Posttraumatic Fibro-Osseous Lesion of the Rib: A Rare and Underrecognized Entity. Case Report and Literature Review

Post-traumatic Fibro-Osseous Lesion of the Fourth Rib Simulating a Chest Wall Tumor: A Case Report

Post-traumatic fibro-osseous lesions (PTFOL) are a rare and benign tumor that typically affects the ribs and is probably caused by an excessive post-traumatic reactive process. PTFOL primarily affects the sixth, seventh, and eighth ribs. Here, we report a case of a PTFOL with an unusual location and expansion that simulated a malignant chest tumor. A 28-year-old male patient with a history of minor chest trauma presented with pain. Chest radiography revealed a large, well-defined lesion on the left fourth rib, and computed tomography (CT) of the chest revealed a lytic lesion-type IC on the posterior and middle arches of the left fourth rib with a cartilaginous matrix and discontinued periosteal reaction without soft tissue mass extension. Additionally, magnetic resonance imaging of the chest revealed an ovoid, expansive mass with cystic lobules and lobulated contours extending almost over the entire left fourth rib, measuring 134×47 mm in size. This mass has a low signal on T1-weighted images and a heterogeneous intermediate signal on T2-weighted images, with intense enhancement after gadolinium injection suggestive of a malignant chest tumor. A CT-guided bone biopsy confirmed the presence of an intramedullary lesion consisting of fibrous connective tissue with fusiform fibroblastic cells without atypical signs. The lesion was delimited by bone trabeculae with nibbled edges, indicating exaggerated osteoclastic activity compatible with a diagnosis of PTFOL. The patient was treated with simple analgesics, and chest pain was relieved, with an unchanged volume of the lesion at 1 year of follow-up.

Primary Intraosseous Xanthomas of the Jaws: A Series of Six Cases Including an Example with Formation of Apoptosis-Related Hyaline Globules, So-Called "Thanatosomes"

Primary intraosseous xanthomas of the jaws (PIXJ) are rare and predominantly affect the posterior mandible (86%) of normolipemic patients, with a mean age of 30 years and no gender predilection. Clinically, PIXJ exhibit indolent biologic behavior; curettage is considered treatment of choice. Only 36 PIXJ have been reported. Apoptosis-related hyaline globules (HGs), also known as "thanatosomes", have not been previously reported in PIXJ. Cases diagnosed as xanthoma of bone were retrieved. Six cases fulfilling currently accepted criteria were identified and their clinicopathologic and immunohistochemical properties are presented herein. Mean age for PIXJ was 21.8 years (range = 12-33) and F:M ratio = 2:1. All cases presented as well-demarcated, unilocular or multilocular radiolucencies. Microscopically, PIXJ featured sheets of lipid-laden macrophages with eosinophilic or foamy cytoplasm. A secondary fibroblastic population lacking storiform pattern was evident in two cases. Adipocytes (3/6), peripheral neurovascular bundles (1/6), bone fragments (3/6) and dystrophic calcifications (3/6) were observed enclosed by the xanthoma cells. Notably, one case exhibited numerous, spherical, eosinophilic HGs containing apoptotic nuclei. PIXJ were consistently CD68(+) and negative for CD1α and S100. CD45 decorated lymphocytes and the membrane of foamy histiocytes. Xanthoma cells stained for lysozyme and plasma proteins including alpha-1 antitrypsin (AAT), IgG and IgA in one probed case. HGs were lysozyme(+), AAT(+), IgG(+), IgA(+), PAS(+) and diastase-resistant, and fuchsinophilic with Masson's trichrome. PIXJ represent infrequent, solitary, mandibular lesions with a predilection for the second and third decade of life. Thanatosomes associated with cell injury and death can be present in PIXJ.