A Report of Two Cases and Review of the Literature.'' 1 Dr. Gilcrease references his study of crystals in salivary gland neoplasms, which was published after ours was submitted for review. 2 We regret not having had a chance to include his findings in our discussion. Dr. Gilcrease suggests that the crystals that were described in our articles 1,2 are similar and best termed ''tyrosine-rich'' crystals. We disagree. This is not only because our crystals do not resemble the classic floret-like tyrosine crystals associated with pleomorphic adenomas. 3 Johnson et al. 5 studied crystals morphologically similar to those described in Dr. Gilcrease's and our articles. Ultrastructural and chemical analysis led Johnson et al. to propose that they represent crystallized salivary alpha-amylase. 5 In addition, these authors showed that the crystalloids were immunoreactive for human salivary alpha-amylase.
By choosing the term ''non-tyrosine'' we do not intend to imply that there is no tyrosine in these crystals. In fact, a complex protein such as alpha-amylase contains some tyrosine. Not surprisingly, one of the cases reported by Johnson et al. and referenced by us did show some staining for tyrosine. Dr. Gilcrease argues that these crystalloids are ''tyrosine-rich'' because they showed red-brown color when exposed to Millon's reagent. Millon's agent is a histochemical stain of unclear specificity which produces a red color in the presence of phenols such as found on tyrosine. 6 A positive Millon's stain may therefore be seen with a protein such as alpha-amylase that contains some tyrosine. We believe that, although the precise composition of the crystals we described is undetermined, the most sophisticated analysis to date 5 suggests they are not composed primarily of tyrosine but rather of alpha-amylase or a similar protein. Thus, we prefer the term ''non-tyrosine'' crystalloids to distinguish them from the tyrosine-rich crystals associated with some parotid tumors.