Challenges in Diagnosing Medication Resins in Surgical Pathology Specimens: A Crystal-Clear Review Guide

Abstract

Context.— Medication resins, including Kayexalate, sevelamer, and bile acid sequestrants, can be encountered in gastrointestinal tract specimens. Their classic histologic appearances have been well documented, but pathologist recognition of the resins is 75%, patient history is not always available, and atypical morphologic findings are sometimes present. Objective.— To offer a succinct overview of resins in the gastrointestinal tract, including typical and atypical appearances, in order to serve as a quick reference guide. Data Sources.— The study comprises published literature, survey data, and our personal experiences. Conclusions.— Classic morphology is the benchmark for identifying these resins, but color, location, and fish scale pattern can deviate from the norm, making proper identification a challenge. Patient history should be sought whenever possible, and ancillary staining is an option when necessary. Additionally, the presence of resins should prompt the pathologist to search for potentially related diagnoses (namely, causes of diarrhea in patients on bile acid sequestrants and diagnoses associated with renal failure in patients on Kayexalate or sevelamer).

"Fish-scales" and graft nephrectomy: unexpected findings at an unusual site

“…These being administered orally or as enema are usually seen in gastrointestinal mucosal biopsies with characteristic morphologic appearances. Kayexalate crystals display mosaic pattern of rectangular shaped "fish-scales" with perpendicular points of intersection, are purple on hematoxylin & eosin (H&E), turn magenta on PAS/D and stain black with acid-fast stains (1,3,5). Sevelamer crystals are non-polarizable with broad, curved, and irregularly spaced "fish-scales" and display a 2-toned color imparted by bright pink linear accentuations and a rusty yellow background.…”

“…They acquire magenta color on AFB stain and a violet color on PAS/D and maintain their internal structure (4). Fish-scale patterns can be produced by gall bladder calculi, dystrophic calcifications, food particles, large bile acid sequestrant fragments and specimen ink (5). Cruising the entire slide for definite features of the crystals elsewhere, supported by ancillary special stains such as acid fast -bacillus stain and PAS/D is helpful in circumventing these issues although the latter stain is reported to be inconsistent.…”

Unique causes of esophageal inflammation: a histopathologic perspective

“…Sevelamer carbonate crystals are generally more irregular in shape than sodium polystyrene sulfonate crystals, are nonpolarizable, and have been described as varying in color, but are often eosinophilic to golden brown or purple. Sevelamer carbonate crystals have been described as having a fish‐scale appearance, although the fish‐scale appearance is not entirely specific for sevelamer and can be seen in other resins, including sodium polystyrene sulfonate . Sevelamer carbonate has been reported to cause chronic mucosal injury and superficial necrosis of the esophageal mucosa …”

“…Sevelamer carbonate crystals have been described as having a fish-scale appearance, 41 although the fishscale appearance is not entirely specific for sevelamer and can be seen in other resins, including sodium polystyrene sulfonate. 42 Sevelamer carbonate has been reported to cause chronic mucosal injury and superficial necrosis of the esophageal mucosa. 41 Certain systemic medications are also associated with endoscopic and histologic changes in the esophagus.…”

Pathology of resin-induced gastrointestinal damage: report of 15 cases and review of literature

“…One of the main distinctive features of resin mucosal damage is the identification of resin crystals. This is reported in roughly in 75% of cases according to a study by Gonzalez et al (13). It is logical to think that familiarity of the reporting pathologist with the different morphological appearances of such resins coupled with a high index of suspicion with clinical correlation is crucial.…”