Lipoblastoma-like tumor of the vulva: further characterization in 8 new cases.

Lipoblastoma-like tumor of the vulva (LLTV) is an exceptionally rare adipocytic mesenchymal tumor with only 4 cases reported previously. The aim of this study is to help characterize this tumor type. Eight cases of LLTV were identified in the consult files of one of the authors (C.D.M.F.). Clinical data and follow-up information were obtained from the referring pathologists. Detailed clinical information is available in all 8 cases. Patient age ranged from 17 to 46 years (median 27 y). Lesions presented as a vulvar mass with a variable growth rate, sometimes being painful. The most common preoperative clinical diagnosis was a Bartholin gland abnormality (4). The size of the mass ranged from 3.5 to 15 cm (median 5.6 cm). The lesions were described as grossly myxoid, mucoid, or gelatinous (4), well defined (4), and lobulated (3). None of the lesions exhibited necrosis. Histologically, LLTVs were lobulated and composed of variable proportions of mature adipocytes, bland univacuolated and bivacuolated lipoblasts, and spindle cells with short stubby nuclei in a diffusely myxoid background with prominent branching vessels. Nuclear atypia was minimal. No necrosis and only rare mitotic activity was identified. Only 1 of 7 tumors (in a 26-y-old patient) was positive for PLAG1 and retinoblastoma (Rb). Rb was lost, and PLAG1 was not expressed in all other tumors. HMGA2 was negative in 6 of 6 cases tested. Tumors were negative for S100 (5/5), MDM2, and CDK4 (5/6; 1 with just scattered cells positive for both antibodies). Two of 5 cases were positive for CD34. Fluorescence in situ hybridization for DDIT3 gene rearrangement was negative in 5 cases tested. The follow-up interval ranged from 4 months to 11 years (median 2.75 y). Three patients developed 1 local recurrence, 7 months, 2 years, and 8 years, respectively, after excision of the primary tumor. None of the patients has developed metastatic disease. LLTVs are indolent adipocytic mesenchymal tumors arising in adults. Lack of PLAG1 and HMGA2 expression in the majority of LLTV suggests that these lesions are distinct from "true" lipoblastoma. The loss of Rb in the majority of cases suggests a possible role of 13q chromosomal alterations and a possible relationship with the spindle cell lipoma tumor family.