Fine-Needle Aspiration of Malakoplakia Presenting as a Peri-rectal Mass after Intestinal Transplant.

This case highlights the potential risk factors associated with the development of malakoplakia and demonstrates the important role of fine-needle aspiration (FNA), which can lead to rapid diagnosis and exclusion of more serious entities.

A male patient in his thirties developed short gut syndrome secondary to operations to treat bowel perforation injuries. The patient underwent a small and large bowel transplant and was subsequently treated with immune suppressors. His course was complicated by three episodes of acute rejection and a septate fluid collection surrounding the rectum. Drainage of the fluid was performed and Escherichia coli was isolated; in addition, blood cultures at the time isolated Klebsiella oxytoca. A PET/CT scan revealed fluorodeoxyglucose (FDG) avid lymphadenopathy in the mesentery and increased FDG uptake in what was thought to be a peri-rectal “mass.” In addition, the patient was found to have a positive quantitative EBV blood test. The decision to perform an endoscopic FNA of the peri-rectal “mass” was made. The endoscope was introduced through the anus and advanced to the rectum, where a clean based ulcer with an underlying prominent bulge was noted. On endoscopic ultrasound, a 32.1 mm in greatest dimension hypoechoic lesion in the perirectal space was visualized, corresponding to the region of the ulcer and bulge seen on endoscopy. Two passes with a 22-gauge needle were performed, and the material was subsequently placed in alcohol fixative.

The FNA material was received at the cytology laboratory in alcohol fixative, from which one Papanicolaou (PAP) stained monolayer smear and a cell block were prepared. Sections of the cell block were stained with Hematoxylin and Eosin (H and E), PAS (with and without diastase), Von-Kossa, Prussian blue, AFB, and GMS stains.

On the PAP smear, multiple macrophages with abundant granular cytoplasm were present. Some of the macrophages contained pathognomonic Michaelis–Gutmann (M-G) bodies, with many of these bodies additionally identified in the extracellular space [Figure 1a]. H and E stains of cell block sections revealed similar findings [Figure 1b]. On special stains, the M-G bodies were positive with Von-Kossa and PAS-diastase resistant [Figure 1c] and negative for iron. AFB and GMS stains for microorganisms were negative. Taken together, these results supported the diagnosis of malakoplakia.

Figure 1

(a) Pap stain of alcohol-fixed FNA aspirate (original magnification of 40×) with multiple macrophages and M-G bodies (red arrows). (b) Corresponding cell block preparation (original magnification of 40×) (M-G bodies, green arrows). (c) Special stains of the cell block material (original magnification of 40×), showing the characteristic staining pattern of the M-G bodies, including PAS positivity (left, yellow arrows) and Von-Kossa positivity (right, blue arrows)

Malakoplakia is a chronic granulomatous disease of unknown etiology, involving macrophage lysosomal-bactericidal defects in the context of bacterial infection or immune suppression.[1] The urinary bladder, kidney, and colon are the organs most commonly involved.[12] Tissues involved by malakoplakia reveal macrophages with abundant cytoplasm containing the pathognomonic M-G bodies, concentrically layered basophilic inclusions, likely representing partially digested bacterial cell wall products in the phagolysosomes of macrophages.[1]

Organ transplant patients exhibit many risk factors for developing malakoplakia. Most reports concerning transplant patients have occurred in the context of renal transplant, with fewer reports implicating liver and heart transplant.[34] Our patient was on a variety of immunosuppressive medications for rejection prophylaxis of an intestinal transplant. A peri-rectal abscess containing Escherichia coli and bacteremia with Klebsiella oxytoca was also demonstrated, both of which species have been associated with developing Malakoplakia. Although these risk factors for malakoplakia were known, this unusual disease was not considered in the original differential diagnosis.

Several other important differential diagnoses were considered at the time of FNA of the rectal “mass.” Post-transplant lymphoproliferative disorder was a serious consideration, supported by the finding FDG avidity on PET/CT and a positive quantitative blood test for EBV. Another important consideration for the “mass” was neoplasia. Infection with mycobacterial and fungal species can lead to granulomatous inflammation with abundant histiocytes and can complicate immunocompromised states.

FNA cytology in the evaluation of our patient revealed abundant macrophages containing M-G bodies with special stain characteristics in concordance to what has been described in the literature.[5] Negative GMS and AFB stains confirmed the absence of demonstrable fungal and acid-fast organisms. Taken altogether, these findings lead to the diagnosis of malakoplakia.

FNA-based diagnosis of malakoplakia is unusual but has been previously described.[56] The rapidity and the relative ease of access to samples compared with biopsies make FNA an attractive initial approach for lesions in patients with specific risk factors. Given that malakoplakia is an unusual and challenging diagnosis to make clinically and a broad differential diagnosis must be entertained, cytology can prove helpful, especially in avoiding diagnostic pitfalls. In addition, our patient highlights the multiple risk factors for developing malakoplakia associated with bowel transplant patients. To our knowledge, this is the first report of malakoplakia in an intestinal transplant patient.

Ethical Approval

Not applicable. Per the MedStar Office of Research integrity, case reports including 3 or fewer individuals do not meet the U.S. Department of Health and Human Services (DHHS) definition of research and therefore do not require Institutional Review Board (IRB) review but are still subject to Health Insurance Portability and Accountability Act of 1996 (HIPAA) requirements. No Protected Health Information (PHI) was disclosed during the preparation of the case report.

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Conflicts of interest

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