Radiologic-Pathologic Correlations Dedifferentiated chordoma of the thoracic spine with rhabdomyosarcomatous differentiation. Report of a case and review of the literature Michele Bisceglia, MD a, 4 , Vincenzo Antonio D’Angelo, MD b , Giuseppe Guglielmi, MD c , David Ben Dor, MD d , Gianandrea Pasquinelli, MD e a Department of Pathology, Division of Anatomic Pathology, IRCCS bCasa Sollievo della SofferenzaQ Hospital, I-71013 San Giovanni Rotondo (FG), Italy b Department of Neurosciences, IRCCS bCasa Sollievo della SofferenzaQ Hospital, I-71013 San Giovanni Rotondo (FG), Italy c Department of Radiology, IRCCS bCasa Sollievo della SofferenzaQ Hospital, I-71013 San Giovanni Rotondo (FG), Italy d Department of Pathology, The Barzilai Medical Center, Ashkelon IL-78306, Israel e Department of Clinical Pathology, Policlinico bS OrsolaQ Hospital, I-40138 Bologna, Italy Abstract A case of spinal thoracic chordoma involving the T9 vertebra in a 70-year-old male patient, destroying the vertebral body and invading the vertebral canal with compression of the spinal cord, is presented. The patient was referred to our neurosurgical unit with a history of an irradiated metastatic adenocarcinoma to the thoracic vertebra, a diagnosis that was rendered 3 years earlier at another hospital on presentation. This misdiagnosis was likely due to the absolute rarity of thoracic vertebral chordomas (2%-3% of all chordomas), the higher frequency of metastatic deposits to the vertebrae from visceral cancers in the elderly, the limited amount of biopsy material available for histologic examination, and the epithelial phenotype of the tumor (keratin/EMA positive). The patient underwent second palliative surgery with subtotal piecemeal removal of the tumor bringing relief of the neurologic symptoms. The bulk of the tumor was represented by a high-grade pleomorphic sarcoma with adjacent areas of atypical chordoma. Small foci of conventional chordoma were also found. The previous histologic slides were also reviewed, which were consistent with the areas of atypical chordoma. Small targeted tissue fragments from areas of (atypical) chordoma and from sarcomatous areas were recovered for electron microscopy. The fine features of chordoma and focal rhabdomyoblastic differentiation were found with the latter retrospectively supported by immunohistochemical detection of striated muscle markers. A final diagnosis of dedifferentiated chordoma with rhabdomyoblastic differentiation was finally established. Rhabdomyoblastic metaplasia is a novelty in dedifferentiated chordoma. The patient died after 5 months. Autopsy was not requested. D 2007 Elsevier Inc. All rights reserved. Keywords: Thoracic spine; Chordoma; Physaliphorous cells; Dedifferentiation; Rhabdomyosarcoma 1. Introduction Chordoma is a rare tumor with phenotypical epithelial features arising from notochordal rests, comprising 1% to 4% of all bone tumors [1-3]. In general, it is a slowly growing tumor, prone to recurrences, and capable of distant metastases [1- 4]. Chordoma of the mobile spine (true vertebral chordoma) represents the least common clinical subset (15%) of this entire category of tumors, and chordoma of the thoracic spine is the most uncommon 1092-9134/$ – see front matter D 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.anndiagpath.2006.09.002 Case presented in part at the IV International Postgraduate Course in Soft Tissue Tumor Pathology. Bolzano, Italy, 5-7 June 1997 (abstr in Pathologica 1998;90:200-201). 4 Corresponding author. Tel.: +39 0882 410366; fax: +39 0882 410411. E-mail addresses: bismi@libero.it, m.bisceglia@operapadrepio.it (M. Bisceglia). Annals of Diagnostic Pathology 11 (2007) 262 – 273