CONTEXT: Calcineurin inhibitor toxicity [CNI] is a major cause of posttransplant renal impairment. Its prompt recognition is essential in renal transplant management.
DESIGN: A retrospective study on 162 cases of kidney transplant core biopsies were reviewed over the last 4 years in our Nephropathology Department. The diagnosis of CNI was rendered in 54 cases [33%]; while rejection was rendered in 78 cases [48%]. In all cases, C4d and CD68 were performed by immunohistochemistry on formalin fixed, paraffin embedded tissue. The pattern of CD68 positivity was then analyzed into two patterns: histiocyte staining pattern and tubular epithelium granular pattern.
RESULTS: C4d was positive in 44 out of 162 cases [27%]. CD68 was positive in 133 cases out of 162 [83%]. The pattern of CD68 positivity was then analyzed into two patterns: histiocyte staining pattern in 82 out of 162 cases [51%], and tubular epithelium granular pattern in 53 out of 162 cases [33%]. In the remaining 27 cases [16%], both patterns are seen within the same case. 53 [out of 54 cases: 98%] with CNI showed tubular epithelium granular pattern at least focally. On the other hand, only one case with rejection out of 78 cases [1%] showed granular tubular epithelium pattern.
CONCLUSION: CD68 immunostaining in tubular granular pattern in biopsies from kidney transplant patient is an excellent marker for diagnosing CNI in kidney transplant patients.
