Pleomorphic rhabdomyosarcoma showing smooth-muscle and fibrohistiocytic differentiation: a single case report

Immunohistochemical Characterization of Sarcomas in Trp53+/- Haploinsufficient Mice

The use of immunohistochemical (IHC) staining in determining and/or confirming the cellular origin of poorly differentiated sarcomas was evaluated in this study. Sarcomatous neoplasms were evaluated in a research study conducted in 2 strains of p53+/- haploinsufficient mice. The most common neoplasms were undifferentiated sarcomas, followed by osteosarcomas and rhabdomyosarcomas (RMSs). The RMSs were poorly differentiated and appeared similar to the pleomorphic, or adult type, RMS of humans. All sarcomas stained positive by IHC for the mesenchymal cell intermediate filament vimentin. The RMSs were identified by positive IHC staining for myogenin, a transcription factor specific to skeletal muscle. Osteosarcomas were easily identifiable on hematoxylin and eosin-stained slides; no generally accepted IHC stain specific for bone is presently available. Some of the undifferentiated sarcomas contained numerous macrophages that stained positive for F4/80, a macrophage marker; the positive-staining cells were considered to be infiltrating macrophages. One-third of the neoplasms observed in this study were associated with subcutaneous implanted electronic microchips used for animal identification. Based upon histopathologic evaluation and IHC staining, it was not possible to distinguish neoplasms associated with subcutaneous microchips from neoplasms not associated with microchips.

A pleomorphic rhabdomyosarcoma mimicking an inguinal hernia: a case report and review of the literature

A 59-year-old male presented with a painful right inguinal swelling and deep vein thrombosis at the ipsilateral leg. An inguinal hernia was initially diagnosed, but during surgery a large mass was found anteriorly to the peritoneal sheaths. Histology revealed a high-grade pleomorphic rhabdomyosarcoma. The mass advanced rapidly, occupying the whole right iliac fossa and metastasizing to the lung. Despite first- and second-line chemotherapy, the patient deteriorated rapidly and died. Rhabdomyosarcomas should be managed in specialized centres as they have prognostic factors and histologic features still controversial and poorly clarified.

Aggressive spindle cell rhabdomyosarcoma in an 11-month-old boxer dog

Rhabdomyosarcoma (RMS) is a malignant neoplasm derived from mesenchymal tissue with a tendency toward myogenic differentiation associated with the embryogenesis of skeletal muscle. According to the histological features, it can be classified in embryonal, botryoid, alveolar, and pleomorphic, which usually correspond to clinical behavior and prognosis. The spindle cell (SCRMS) variant is a rare subtype of the embryonal RMS and is considered to be less aggressive lesion. The aim of the present paper is to report an unusual case of SCRMS in an 11-month-old male boxer dog diagnosed as extensive SCRMS that affected the frontal region of the skull. Due to the aggressive nature of the lesion and poor clinical prognosis the dog's owners preferred euthanasia as a treatment. A full postmortem examination was carried out. Microscopically, the lesion was composed of a highly cellular proliferation of spindle cells arranged in long and intersecting fascicles. After performing the immunohistochemical studies (HHF-35, smooth muscle actin, desmin and MyoD1), the present case was diagnosed as SCRMS.