Malacoplakia manifesting as a chronic inflammatory mass at the site of a nonhealing surgical wound.

Abstract

Malacoplakia in the head and neck is uncommon, and malacoplakic lesions involving the thyroid are extremely rare. The author describes the case of a 64-year-old woman who developed malacoplakia at the site of a previous total thyroidectomy. The disease manifested as a chronic inflammatory mass beneath a persistently discharging surgical wound site, and it prevented the incision from healing. Diagnosis was based on a thorough histopathologic analysis.

Introduction

Wound complications--including bacterial infection, hematoma, evisceration, suture abscess, and dehiscence--are not uncommon following surgery. However, it is rare to encounter a nonhealing wound with a persistent discharge in the absence of malignancy, chronic granulomatous lesions, or foreign bodies.

Malacoplakia is an uncommon and distinct chronic inflammatory reaction of unknown origin. It is characterized by an infiltrate of lymphocytes, plasma cells, and large granular or foamy histiocytes associated with laminated bodies--the so-called Michaelis-Gutmann (MG) bodies. Involvement of sites in the ear, nose, and throat is rare. Malacoplakia can involve surgical wound sites and prevent them from healing, but to the author's knowledge, only one such case has been previously reported. (1) In this article, the author describes a new case of malacoplakia involving a surgical wound. In this case, the malacoplakia manifested as a persistently discharging and nonhealing surgical wound and a chronic inflammatory mass at the site of a previous total thyroidectomy.

Case report

A 64-year-old woman came to the ENT department with a rapidly growing left neck mass and a persistently discharging, nonhealing surgical wound. Nine months previously, she had undergone a total thyroidectomy for diffuse toxic goiter, which had been diagnosed on the basis of clinical features and ultrasonography. Pathology had revealed nodular hyperplasia in the fight lobe of the thyroid, and follicular adenoma with areas of severe acute and chronic inflammation and foci of abscesses in the left lobe. The surgical incision site had not healed, and granulation tissue with chronic discharge developed. Four months later, the wound was debrided, and culture identified Escherichia coli. Despite intensive therapy with appropriate antibiotics, the wound still had not healed.

The wound site was erythematous. Palpation revealed that the mass beneath it was firm and tender. Hematologic testing revealed the presence of a significant inflammatory syndrome; the patient's erythrocyte sedimentation rate was 135 mm/hr, her C-reactive protein level was 204 mg/l, and her white blood cell count was 19,000/[mm.sup.3]. Computed tomography (CT) of the head and neck, with and without contrast, detected an increased amount of subcutaneous fatty stranding at the submental and neck regions, a finding compatible with cellulitis (figure 1). CT also demonstrated an irregular lobulated hypodensity with air inclusion that extended from the left lateral compartment of the neck to the paratracheal space.

Open exploration revealed a deep necrotic mass with a cavitating lesion that extended along the left paratracheal space and surrounding dense induration secondary to severe fibrosis. Extensive debridement was performed. The intraoperative culture grew E coli and Klebsiella species. Postoperatively, the patient was maintained on antibiotic therapy with metronidazole and ceftriaxone.

During surgery, multiple fragments of dark-brown tissue measuring up to 8.6 x 3.5 x 2 cm were obtained for analysis. Histopathology of both the deep debrided tissue and the overlying epidermis revealed sheets of polygonal histiocytes with foamy or fine granular eosinophilic cytoplasm intermingled with lymphocytes, plasma cells, and neutrophilic leukocytes (figure 2). Areas of abscess were also noted. Several histiocytes contained dense intracellular basophilic to targetoid inclusions and appeared to be typical MG bodies. The inclusions were positive on periodic acid-Schiff (PAS) staining, diastase-resistant von Kossa's staining (figure 3), and Prussian blue staining. Strong positivity was also observed on immunohistochemistry for CD68. No micro-organisms were identified on Gram's, silver, or Ziehl-Neelsen staining. Based on these findings, a pathologic diagnosis of malacoplakia was made. A review of the slides obtained during the patient's thyroidectomy revealed the same morphologic findings.

Discussion

Malacoplakia is an unusual yet well-documented form of chronic xanthogranulomatous inflammation. The pathogenesis of malacoplakia has not been fully elucidated, but it is generally considered to be related to an acquired defect in macrophage phagocytic bactericidal activity against bacterial pathogens, especially E coli. Phagolysosomes that are unable to digest their contents form the pathognomonic MG bodies. (2) It has been suggested that the basic defect is a cyclic 3',5'-guanosine monophosphate dehydrogenase deficiency, which results in a decrease in lysosomal breakdown and diminished microbial killing. (3)

Malacoplakia in the urinary bladder should rarely cause diagnostic problems because most pathologists are aware of the condition in this location. However, diagnosis outside the genitourinary tract may be difficult because of a lack of awareness, the presence of only a few MG bodies, poor staining of MG bodies on hematoxylin and eosin (H&E) analysis, or a failure to use special stains to enhance the detection of MG bodies. Furthermore, in the absence of a careful inspection for MG bodies, the clinical picture and histologic features may be incorrectly interpreted as a nonspecific inflammatory process. On the other hand, microscopic features are not always dominated by infiltrates of histiocytes with granular cytoplasm and typical targetoid bodies. Frequently, neutrophils, plasma cells, and lymphocytes make up most of the cells, and they are often accompanied by abundant granulation tissue that can evolve into classic malacoplakia over time, as was seen in our case.

Many patients with malacoplakia have had associated bacterial infections, most often E coli infection. Much less frequently, micro-organisms have been identified within histiocytes in the lesion. Cutaneous malacoplakia can manifest as abscesses, masses, draining sinuses, papules, nodules, or ulcerations. (4) Most reported cases of cutaneous malacoplakia were isolated--that is, no other organ or tissue was involved. (5,6) Only rare cases of cutaneous malacoplakia associated with other organs have been described. (1,7)

Malacoplakia of the thyroid is very rare. It may be associated with hyperplastic or neoplastic follicular disease, and bacterial infection could be an important factor in its etiology. Only a few cases of a follicular lesion associated with malacoplakia of the thyroid have been published. (8,9)

With regard to the prognosis, malacoplakia is a heterogeneous disease with different patterns of aggressiveness. Variations in its clinical behavior could be related to the location of the disease and the degree of local invasion at the time of diagnosis and treatment.

Although malacoplakia was not initially considered in our patient, our intensive review of surgical specimens and careful inspection for MG bodies with various special stains ultimately led us to the correct diagnosis. Therefore, we recommend that malacoplakia be included in the differential diagnosis of nonhealing wounds with persistent discharge in the presence of an inflammatory mass at the wound site. Treatment with extensive debridement and antibiotic therapy should be adequate.

References

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(2.) Lou TY, Teplitz C. Malakoplakia: Pathogenesis and ultrastructural morphogenesis. A problem of altered macrophage (phagolysosomal) response. Hum Pathol 1974;5:191-207.

(3.) Abdou NI, NaPombejara C, Sagawa A, et al. Malakoplakia: Evidence for monocyte lysosomal abnormality correctable by cholinergic agonist in vitro and in vivo. N Engl J Med 1977;297: 1413-19.

(4.) McClure J. Malakoplakia. J Pathol 1983:140:275-330.

(5.) Douglas-Jones AG, Rodd C, James EM, Mills RG. Prediagnostic malakoplakia presenting as a chronic inflammatory mass in the soft tissues of the neck. J Laryngol Otol 1992;106:173-7.

(6.) Lowitt MH, Kariniemi AL, Niemi KM, Kao GF. Cutaneous malacoplakia: A report of two cases and review of the literature. J Am Acad Dermatol 1996;34(Pt 2):3325-32.

(7.) Kogulan PK, Smith M, Seidman J, et al. Malakoplakia involving the abdominal wall, urinary bladder, vagina, and vulva: Case report and discussion of malakoplakia-associated bacteria. Int J Gynecol Pathol 2001:20:403-6.

(8.) Larsimont D, Hamels J, Fortunati D. Thyroid-gland malakoplakia with autoimmuue thyroiditis. Histopathology 1993;23:491-4.

(9.) Katoh R, Ishizaki T, Tomichi N, et al. Malacoplakia of the thyroid gland. Am J Clin Pathol 1989;92:813-20.

From the Department of Pathology, Chang-Gung Hospital and Chang-Gung University, School of Medicine, Linkou, Taoyuan, Taiwan.

Reprint requests: Leou-Chuan Pang, MD, FCAP, Department of Pathology, Chang-Gung Hospital and Chang-Gung University School of Medicine, Linkou, Tauyuan, Taiwan. Phone: [phone], ext. 2746; fax: [phone]; e-mail: [e-mail]