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Correspondence |
Charles University Medical Faculty Pilsen, Czech Republic
To the Editor-in-Chief:
In the interesting study of chordomas, Gottschalk et al1 suggest that some cartilaginous tumors could be, in fact, chondroid chordomas in which complete cartilaginous differentiation occurred. Nevertheless, the authors mention that such a phenomenon seems to them as an unlikely extreme, analogous to pleomorphic adenoma of the salivary gland with unidirectional cartilaginous differentiation (chondroma-like pleomorphic adenoma) that was not described, and that such an event still only represents a theoretical possibility. However, I remember that a case of a salivary gland pleomorphic adenoma composed exclusively of cartilage had been described in a study of salivary gland neoplasms by Gusterson et al.2 This tumor showed morphology of typical chondroma and its epithelial nature was manifested only in a form of epithelial membrane antigen positivity. This observation can support the above-mentioned suggestion by Gottschalk et al1
I believe that modern ancillary techniques will discover, in the future, further lesions with unidirectional cartilaginous differentiation derived from a non-cartilaginous or non-mesenchymal cell. An interesting example for this is a case of a morphologically typical low-grade chondrosarcoma in which only a cytogenetic analysis was able to prove a germ cell origin.3
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University of Erlangen-Nurnberg Erlangen, Germany
Author’s Reply:
We are grateful for the comments of M. Zamecnik on our article entitled, "Matrix Gene Expression Analysis and Cellular Phenotyping in Chordoma Reveals Focal Differentiation Pattern of Neoplastic Cells Mimicking Nucleus Pulposus Development."1
He mentions a potentially very interesting tumor case of a salivary gland reported by Gusterson et al2
showing only chondroid and myxoid areas and being positive for EMA. Certainly, this case would be interesting to review, but the question arises whether or not the polyclonal antibodies used were really monospecific. We and others never found (significant) positivity of the chondroid areas of pleomorphic adenomas for epithelial cytokeratins3
or EMA (clone E29 von Dakopatts, Denmark (Figure 1)
).4
Also, the testicular teratoma5 showing complete chondrosarcomatous differentiation is an interesting case although the histology shown in the manuscript does not clearly correspond to conventional chondrosarcoma but rather shows additionally undifferentiated mesenchyme. Again, a reinvestigation of the case with currently available tools would be worthwhile, which would allow identification and classification of chondrocyte differentiation.6,7
Overall, clearly single (ie, very exceptional) cases may exist that represents extreme variants of neoplastic differentiation spectra. Whether this includes chondroma-identical pleomorphic adenoma and chondrosarcoma-identical chondroid chordoma requires further investigations. However, one should not forget, in practice, that these "extreme" cases are very rare–if they exist at all. Thus, particularly in cases in which the neoplastic counterparts (ie, chondrosarcoma for chondroid chordomas) are rather common, one should be very reluctant not to take these as a first diagnostic choice, even though this might, in a very exceptional case, be wrong.
References
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