Two Cases of Liposarcoma in the Head and Neck Region: Diagnostic Usefulness of Detection of MDM2, CDK4, and p16 Expression

Abstract

Liposarcoma is a commonly encountered sarcoma, that arises predominantly in the extremities or retroperitoneum. According to a study conducted by the Armed Forces Institute of Pathology (AFIP), liposarcoma accounts for approximately 14% of all sarcomas, and only 3.8% of all liposarcomas are found in the head and neck region. Liposarcoma has been classified into four histological subtypes. The clinical features depend on the type of the tumor. Recently, numerous advances have been made in molecular and biologic analyses of liposarcomas, and several gene mutations have been found. These findings are useful for diagnosis of the tumor subtypes. We report two cases of liposarcoma arising in the head and neck region, in which immunohistochemistry was useful for the diagnosis.

Case 1 was a 77-year-old woman who presented with swelling of the left oropharyngeal wall. She had undergone surgery of the left mandible 17 years earlier and was diagnosed as having a lipoma. Surgical resection of the tumor was performed, and the histological diagnosis was liposarcoma (well-differentiated type).

Case 2 was a 23-year-old woman who presented with swelling of the floor of the mouth on the left side. She had undergone operations for an oral floor tumor twice in the previous 10 years. The histological diagnosis on both occasions was liposarcoma (well-differentiated type). Surgical resection was performed again and the histological diagnosis was recurrence of liposarcoma (well-differentiated type).

The tumor showed normal-appearing adipocytes intermixed with atypical adipocytes in both the cases. Immunohistochemical analysis revealed the MDM2+/CDK4+/p16+ immunophenotype in both cases. Immunohistochemistry has proved to be useful for distinguishing among the various subtypes of liposarcoma, in particular, the well-differentiated type.