We would like to thank the authors for their response to our paper1  reviewing the latest iatrogenic foreign materials seen in gastrointestinal specimens. The authors agree that if “the relevant clinical history is lacking,” which unfortunately often is the case, the identification of these materials in the retrieved specimens can pose diagnostic difficulties.

The authors mention the use of 2 ancillary techniques, namely scanning electron microscopy with energy dispersive x-ray analysis and Fourier transform infrared spectroscopy, along with some beautiful illustrations, which can help to identify supplemental material such as lanthanum carbonate in the retrieved tissue. The authors themselves emphasize that these techniques are not available in the majority of centers and hence are not directly accessible to most pathologists. In the selected referral centers where these techniques may be available, they can be expensive and may not justify the cost-benefit proportion. In our personal experience and as stated in our paper1  and well corroborated by other authors,2,3  a diagnosis of lanthanum deposition can usually be made by recognizing the characteristic features on routine histologic sections with confirmation from the medication list. The use of the above ancillary techniques is typically not needed in routine clinical practice. We agree with the authors that in selected cases, wherein the amount of lanthanum deposition is subtle or pathologic features are atypical,2  the use of these ancillary techniques can be helpful.

Chronic clofazimine therapy was referenced in our paper as one of the causes associated with crystal-storing histiocytosis, which may be a histologic differential for lanthanum.1  Our paper by no means intended to address the various disease entities where clofazimine may be used. We agree with the authors that clofazimine is used in the treatment of other disease entities in addition to leprosy treatment.4 

In our review paper,1  we collated the findings of published literature (including recently published research papers) along with our personal experience. And as published by Shaddy (and Arnold) et al5  in their research paper, crospovidone ranged in size from 0.4 to 1.5 mm in diameter and microcrystalline cellulose (MCC) ranged in size from 1 to 2 mm in diameter. The measurements presumably refer to the entire deposit, as these materials are mostly seen in clusters in the retrieved specimens from the gastrointestinal tract and it may be rather difficult or even impractical to measure each crystal separately. The diameter is used as a surrogate for maximum dimension. We agree with the authors that this size measurement would be much smaller if measuring each crystal separately (ie, maximum dimension reported as ≤100 μm for crospovidone and 20–200 μm for MCC).6,7  Of note, in clinical practice, pathologists prefer using other histomorphologic characteristics (ie, crospovidone showing coral or sponge shape with a pink center and purple coat and MCC being recognized as being transparent, with a rod or matchstick shape and brightly birefringent under polarized light) to make a histologic diagnosis of pharmaceutical fillers.5 

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The authors have no relevant financial interest in the products or companies described in this article.