Differentiating between congenital rhabdomyosarcoma versus fibromatosis of the pediatric tongue Shannon M. Kraft a , Vivekanand Singh b , Kevin J. Sykes a , Alan Gamis d , Michelle A. Manalang d , Julie L. Wei a,c, * a Department of Otolaryngology-Head and Neck Surgery, University of Kansas Medical Center, United States b Department of Pathology and Laboratory Medicine, Children’s Mercy Hospital and Clinics, United States c Section of Otolaryngology, Children’s Mercy Hospital and Clinics, United States d Division of Hematology/Oncology, Children’s Mercy Hospital and Clinics, United States 1. Introduction Spindle cell neoplasms account for a unique subset of tumors which may be difficult to diagnose due to histologic similarities. The differential diagnosis in the pediatric population includes benign lesions such as fibromatosis, nodular fasciitis, rhabdo- myoma, nerve sheath tumors such as schwannoma and neurofi- broma, as well as malignant lesions such as fibrosarcoma, synovial sarcoma, leiomyosarcoma, hemangiopericytoma, and rhabdomyo- sarcoma (RMS) [1]. We present two cases of congenital spindle cell tumors of the tongue. By reviewing the radiographic, histologic and immunohistochemical (IHC) features of both cases, we will highlight the difficulty in distinguishing between fibromatosis and spindle cell rhabdomyosarcoma of the head and neck. Case No. 1: A 3.3 kg, 40-week male infant was transferred from an outside hospital shortly after delivery for evaluation of a large, protuberant tongue mass (Fig. 1A). On presentation, the infant was breathing without difficulty despite the size of the tumor. MRI performed on day of life (DOL) 3 demonstrated a 6.3 cm  3.7 cm  3.3 cm heterogeneous mass involving the entire oral and oropharyngeal tongue. The mass enhanced on both T2 and post- contrast T1 images (Fig. 1B and C). On DOL 4, the patient was taken to the operating room for incisional biopsy and tracheotomy. Frozen sections were consistent with a spindle cell neoplasm concerning for rhabdomyosarcoma (RMS). Permanent sections on histological examination revealed sheets of bland spindle cells that infiltrated and effaced the normal striated muscle of tongue (Fig. 2A and B). A few rhabdomyoblastic cells which were both rounded and elongated noted scattered within the spindle cell proliferation. These cells had bright cytoplasmic eosinophilia. However, there were far more numbers of entrapped native striated muscle fibers that showed atrophy and regeneration. IHC staining was patchy and weak for desmin, and negative for CD34 and S-100. There was patchy, but strong nuclear staining for MyoD1 and myogenin (Fig. 2C). Desmin and actin HHF35 were weakly positive in several tumor cells. The tumor was classified as RMS, spindle cell variant. The case was reviewed by Children’s Oncology Group (COG) Rhabdomyosarcoma review committee and their review, concurred with the institutional RMS spindle cell variant diagnosis. The infant was subsequently started on vincristine, doxorubicin and cyclophosphamide per the ARST0331 protocol without radiation. Unfortunately, the tumor was mini- mally responsive to this regimen, and he was switched to COG protocol ARST0431 for additional 6 months. The child has International Journal of Pediatric Otorhinolaryngology 74 (2010) 781–785 ARTICLE INFO Article history: Received 18 January 2010 Received in revised form 28 March 2010 Accepted 30 March 2010 Keywords: Rhabdomyosarcoma Fibromatosis Tongue ABSTRACT Congenital rhabdomyosarcoma of the tongue is exceedingly rare. Fibromatosis of the tongue is also rare, and very difficult to distinguish from the spindle cell variant of rhabdomyosarcoma. Both appear histologically as spindle neoplasms replacing normal striated musculature of the tongue. The treatment protocol for the former has been developed by the Intergroup Rhabdomyosarcoma Studies (IRS) I–IV and requires surgery, radiation, and chemotherapy. For fibromatosis, complete surgical excision is usually adequate without additional therapy, although some cases of aggressive fibromatosis also require chemotherapy. With significant differences in appropriate treatment and prognosis, each entity must not be mistaken for the other. We review the differences in radiologic, histologic, and immunohisto- chemical (IHC) features of both entities. ß 2010 Elsevier Ireland Ltd. All rights reserved. * Corresponding author at: Department of Otolaryngology-Head and Neck Surgery, University of Kansas Medical Center, 3901 Rainbow Blvd., Mail Stop 3010, Kansas City, KS 66160, United States. Tel.: +1 913 945 5071; fax: +1 913 588 6708. E-mail address: jwei@kumc.edu (J.L. Wei). Contents lists available at ScienceDirect International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl 0165-5876/$ – see front matter ß 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijporl.2010.03.057