Lipoblastoma-like tumor of the inguinal region: a close mimicker of myxoid liposarcoma.

Lipoblastoma-like tumor is a rare mesenchymal neoplasm, typically arising in the vulvar region of young women. Although it is considered a benign tumor, rare local recurrences and exceptionally distant metastases have been reported. Histological examination reveals a well-circumscribed tumor with lobulated pattern, composed of a mixture of mature adipocytes, spindle cells and lipoblasts set in abundant myxoid stroma with numerous thin-walled capillary-like vessels. Due to the rarity of this neoplasm and its morphological resemblance with other benign and malignant lipomatous tumors, the diagnosis of lipoblastoma-like tumor is often challenging. Herein, we present a case occurring in the inguinal region of a 28-year-old woman. Histological examination showed a mixture of mature adipocytes, bland-looking spindle cells with fibrillary cytoplasm, and numerous univacuolated lipoblasts set in a prominent myxoid matrix containing numerous thin-walled branching vessels. Immunohistochemically, neoplastic cells showed diffuse immunostaining for CD34 and negativity for α-smooth muscle actin, desmin, Rb1, MDM2 and STAT6. The main differential diagnoses included myxoid liposarcoma, spindle cell lipoma and cellular angiofibroma. FISH was negative for DDIT3; moreover, no evidence of regional gain or loss of RB1 was identified by FISH. Based on morphological, immunohistochemical and cytogenetic/molecular findings, a final diagnosis of "lipoblastoma-like tumor" of the inguinal region was rendered.