Parachordoma is not distinguishable from axial chordoma using immunohistochemistry

Abstract

Parachordoma is a rare soft tissue tumor that morphologically resembles chordoma of the axial skeleton but occurs in a peripheral site. A recent study reported immunohistochemical differences between chordoma and parachordoma. While both tumors were positive for cytokeratin (CK) 8/18 (as recognized by the antibody Cam5.2), S100 and epithelial membrane antigen (EMA), only the chordoma was positive for CK7, CK20, CK 1/5/10/14 (as recognized by the antibody 34betaE12) and carcinoembryonic antigen (CEA). It has since been suggested that tumors indistinguishable from chordoma that involve the periphery should be termed chordoma periphericum and that these tumors are distinct from parachordoma. In the current study, the clinical, radiological, pathological, immunohistochemical and ultrastructural features of a chordoma-like tumor involving the deep soft tissues of the lower leg of a 69-year-old woman are presented. Microscopically, the tumor had a pseudolobulated growth pattern and consisted of sheets, nests and cords of epithelioid cells, some with a physaliferous appearance, separated by abundant myxoid stroma. The tumor cells were positive for CK 8/18, EMA and S100, showed focal staining for CK7, and were negative for CK20, CK 1/5/10/14 and CEA. On the basis of these results a diagnosis of parachordoma was favored. For comparison, an immunohistochemical analysis of five axial chordomas was also performed. The chordomas showed positivity for CK 8/18 (5 of 5 cases), EMA (5 of 5 cases), S100 (5 of 5 cases), CK 1/5/10/14 (1 of 5 cases) and CK7 (1 of 5 cases). Stains for CK20 and CEA were negative in all five chordomas. The results of the present study suggest that the expression of antigens for CK 1/5/10/14, CK7, CK20 and CEA in chordoma might not be as common as what has been previously reported. The results also suggest that parachordoma might not be easily distinguished immunohistochemically from axial chordoma (and therefore also from so-called chordoma periphericum).

Primary Intestinal and Vertebral Chordomas in Laboratory Zebrafish (Danio rerio)

“…9 Extraskeletal soft-tissue chordoma does exist, is extremely rare, and is histologically, immunohistochemically and behaviorally distinct from parachordoma, the former having metastatic potential that is absent in the latter. 9,15 The distinction between chordoma and parachordoma also takes on clinical significance in humans, as the former is invasive and likely to recur following surgical excision. It should be noted, however, that post-resection local recurrence of parachordomas has been reported.…”

“…It should be noted, however, that post-resection local recurrence of parachordomas has been reported. 15 Gastrointestinal involvement by parachordoma is uncommon in humans, with only a single report of a primary tumor in the gastric serosa. 18 …”

“…7,9,15,21 Chordomas are also variably positive for CK20, CK 1/5/10/14, and carcinoembryonic antigen. 15 Brachyury is a regulator of embryonic notochord formation, and chordomas are positive for brachyury expression, whereas parachordomas are negative. 13 Attempts to detect brachyury in formalin-fixed paraffin embedded zebrafish were unsuccessful.…”

Possible parachordoma in a dog

“…Those authors also noted that chordomas expressed similar antigens and also CK 1/10, which parachordomas did not. Scolyer et al (2004) determined that parachordomas and chordomas may not be easily distinguished immunohistochemically because of the overlap in reactivity between the tumours and the differences in individual variability within a tumour type. New Zealand Veterinary Journal 57(5), 2009 301 In summary, the tumour reported here had features consistent with parachordomas reported in people.…”

“…While immunohistochemistry is useful for excluding epithelial and mesenchymal tumours, recent studies have indicated that parachordomas are not easily distinguished from chordomas despite the use of these markers (Scolyer et al 2004).…”