Cerebral pleomorphic liposarcoma: Clinicopathologic findings.

Pleomorphic liposarcoma is the rarest subtype of liposarcoma. Involvement of the central nervous system by pleomorphic liposarcoma is exceptional. We present a 62-year-old woman with an intraparenchymal mass involving the left frontoparietal lobes. Histologic examination demonstrated a mesenchymal neoplasm with a dense reticulin network and pleomorphic lipoblasts. Immunohistochemical stain for adipophilin highlighted intracytoplasmic vacuoles. MDM2 immunostain was negative. A diagnosis of pleomorphic liposarcoma was made. There was no evidence of an extracranial primary neoplasm by imaging or physical exam. Pleomorphic liposarcoma may rarely present as a solitary intracranial mass, an entity that must be entertained in the differential diagnosis of pleomorphic tumors involving the brain.
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Congenital peribronchial myofibroblastic tumor: comparison of fetal and postnatal morphology.

Congenital peribronchial myofibroblastic tumor (CPMT) is a solid pulmonary tumor found in fetuses and neonates with pathology characterized by a proliferation of bland spindled cells with or without irregular cartilaginous islands. It has previously been reported in the literature as a fibrosarcoma, leiomyosarcoma, and hamartoma, among other names. Although complications such as fetal hydrops can occur, the prognosis is generally good if the infant can survive long enough for mass resection. We present a case of a CPMT resected by antenatal fetal surgery at 23 weeks in gestation, with additional tumor resected following birth when the infant was 6 weeks of age. The pathology of this lesion showed a marked increase in the cartilaginous component after birth as well as a decrease in cellularity and mitotic activity. This case presents a unique opportunity to examine the progression of a congenital tumor excised by prenatal and postnatal resections.

Immunohistochemical analysis of hSNF5/INI1 distinguishes renal and extra-renal malignant rhabdoid tumors from other pediatric soft tissue tumors.

Malignant rhabdoid tumor (MRT) is a highly aggressive neoplasm that occasionally demonstrates phenotypic overlap with other soft tissue malignancies. Molecular genetic analysis of MRT frequently demonstrates deletion or mutation of the hSNF5/INI1 gene, with corresponding reduced expression at the protein level. INI1 immunohistochemistry was performed to determine the utility of this method in assessing loss of INI1 expression in rhabdoid tumors. Twenty-seven MRTs with molecular analysis (19 renal, 8 extra-renal) were evaluated. Seventeen additional MRT (10 renal, 7 extra-renal) without INI1 molecular analysis were also analyzed. Loss of INI1 expression was observed in the tumor cells in all 44 cases. To determine the specificity of this assay, a variety of 45 pediatric soft tissue tumors, some of which occasionally display rhabdoid differentiation, were investigated. These included Ewing's sarcoma, Wilms' tumor, desmoplastic small round cell tumor, clear cell sarcoma, congenital mesoblastic nephroma, synovial sarcoma, undifferentiated sarcoma, rhabdomyosarcoma, and epithelioid sarcoma. Positive nuclear staining was found in all nonrhabdoid tumors examined. Of interest, synovial and epithelioid sarcomas exhibited variable and/or focal staining. INI1 antibody immunohistochemistry is useful in confirming the histologic diagnosis of renal or extra-renal rhabdoid tumor, especially for cases with indeterminate histologic features, equivocal immunophenotypic profiles, or uninformative molecular studies.