Collagenous myofibroblastic tumor of the mandible: case report of a unique locally aggressive neoplasm

Odontogenic myxomas lack PDGFRB mutations reported in myofibromas

BACKGROUND

The molecular pathogenesis of odontogenic myxoma has not been established yet. Considering that odontogenic myxoma may show myofibroblastic differentiation and myxoid areas can be observed in intra-osseous myofibromas, we tested the hypothesis whether both tumors share a common molecular profile. As recent studies have reported PDGFRB recurrent driver mutations in myofibroma, we evaluated PDGFRB mutations in odontogenic myxomas.

METHODS

A convenience sample of 15 odontogenic myxomas cases was selected. We direct sequenced PDGFRB exons 12 and 14, where p.R561C (c.1681C>T) and p.N666K (c.1998C>G) hotspot mutations have been reported among others in single and/or multiple myofibromas.

RESULTS

All 15 odontogenic myxoma samples were successfully sequenced, and all 15 had wild-type sequences for the PDGFRB mutations investigated.

CONCLUSION

Our findings suggest that PDGFRB mutations do not play a role in odontogenic myxoma pathogenesis, which might be helpful in the differential diagnosis of challenging cases.

Inflammatory myofibroblastic tumour: A case report and a clinical update

The Inflammatory myofibroblastic tumor (IMT) is a heterogeneous group of rare lesions consisting predominantly of inflammatory cells and myofibroblastic spindle cells. Head and neck IMTs account for 14 to 18% of extra-pulmonary IMTs [lungs being the most commonly affected regions]. On account of its ambiguous clinical presentation, an IMT needs to be differentiated from other infectious, granulomatous, autoimmune and neoplastic lesions on the basis of histopathologic findings and immunohistochemical analysis. In this article, we report a case of IMT that presented in the anterior mandible that was treated by peripheral resection. Follow-up at 1 year showed satisfactory healing and no signs of recurrence. A special emphasis has been placed on the disputed nosology of this lesion and the latest therapeutic modalities.

Myofibroblastoma of the mandible in a 3-year-old child

Myofibroblastoma is a rare benign tumor of the head and neck region, which is characterized by a large, rapidly growing, and destructive mass. A 3-year-old boy presented with an 8-week history of a rapidly growing swelling of the right mandible. Examination revealed a firm 13-cm mass occupying the entire right body and ramus of the mandible. The clinical and radiological features were suggestive of a sarcoma. An initial biopsy taken in the referring hospital was inconclusive, and the second biopsy showed a myofibroblastic neoplasm consistent with a desmoplastic fibroma. Progressive tumor growth necessitated a tracheostomy. Right hemimandibulectomy was performed, and the defect was reconstructed with free microvascular fibula flap. Histopathology and immunocytochemistry revealed a myofibroblastoma. This entity differs from other myofibroblasts and fibroblast tumors such as inflammatory myofibroblastic tumor (IMT), myofibroma, and desmoplastic fibroma. The child has been followed up for 2 years.

CONCLUSION

Differentiation between myofibroblasts and fibroblastic tumors as well as some malignancies can be challenging. Myofibroblastoma can behave as a malignant neoplasm, and the clinical distinction of this entity lies primarily in its recognition as a benign neoplasm.

R, C.H. A. Histogenetic concepts, terminology and categorization of biphasic tumours of the oral and maxillofacial region

A biphasic tumour is a truly histological term that refers to neoplastic tissue which is characterized by two different cellular elements. Several histogenetic theories have been proposed for the aetiogenesis of the biphasic tumours. Literatures have been published on the individual lesions, which have described their biphasic nature but, biphasic tumours have not been categorized singly . Categorizing biphasic tumours is not likely to highlight diagnostic standards, but it may sensitize the therapeutic planning and post operative monitoring. This review article focuses on the histogenetic concepts of biphasic tumours, and the histopathological description of the lesions that are suggested to be biphasic tumours.

Recurrent inflammatory pseudotumor of the jaw with perineural intracranial invasion demonstrating sustained response to Rituximab

Corticosteroids are the mainstay of treatment of inflammatory pseudotumor (IPT) of the head and neck; however, involvement of the skull base and mandible can be unresponsive to steroids and require surgical resection. IPT is known to usually contain a CD20+ lymphocyte subgroup. Rituximab, a chimeric anti-CD20 antibody, has been successfully utilized in the treatment of other CD20+ diseases, including the similar idiopathic orbital inflammatory disease. This is the first report to describe successful treatment with Rituximab of a recurrent IPT of the mandible with trigeminal spread and leptomeningeal involvement with clinical and radiologic evidence demonstrating a sustained response to therapy.