Bellew Elizabeth,  Sonstegard Anna Marie,  Finelt Nika,  Goldfisher Rachelle

Final Pr. ID: Poster #: CR-004

A full-term male was born with a 7 x 7 cm subcutaneous mass with central dark blue discoloration and peripheral erythema on the right flank/buttock. Initial hip and pelvis radiograph at one day old did not show evidence of calcifications. An ultrasound demonstrated an ill-defined, heterogeneous mass with internal vascularity with invasion of underlying muscle. MRI of the abdomen and pelvis with contrast at two days of age showed a T2 hyperintense mass with mild postcontrast enhancement within the right flank with infiltration of the underlying muscles including the right psoas, iliacus, gluteal, and the left erector spinae. The differential diagnosis included: kaposiform hemangioendothelioma, rhabdomyosarcoma (RMS), tufted angioma and neuroblastoma.

Given the broad list of differential diagnoses, a core biopsy of the right buttocks was obtained at 6 days of age to further characterize the lesion. Hematoxylin and eosin stained sections demonstrated highly collagenized and sclerotic spindle cells involving the adipose tissues extending into the dermis. Immunohistochemical stained sections showed positivity to desmin, myogenin and MyoD1. Fluorescence in situ hybridization studies indicated the presence of a VGLL2 gene rearrangement. These pathologic findings were consistent with sclerosing spindle cell RMS. At 13 days old, a PET scan showed the right flank lesion with minimal to no FDG uptake, a finding which is consistent with sclerosing RMS given that this sub-type consists mainly of collagen. There were no pulmonary nodules. After multiple chemotherapy cycles, subsequent MRIs of the abdomen and pelvis showed no residual enhancing lesion. The patient will be closely followed for local recurrence.

RMS, the most common soft tissue tumor seen in children, are mesenchymal tumors of skeletal muscle and are most often seen in head and neck, but are less commonly noted on the flank. Sclerosing spindle cell RMS is a subtype often seen in childhood, but exceedingly rare in newborns. Cutaneous RMS should be considered in the differential diagnosis of a large subcutaneous lesion in a newborn. Read More

Authors:  Bellew Elizabeth , Sonstegard Anna Marie , Finelt Nika , Goldfisher Rachelle

Keywords:  Rhabdomyosarcoma, Sclerosing Spindle Cell Rhabdomyosarcoma, Vascular Malformation