Necrotizing sialometaplasia

Short communications & case reports

Necrotizing sialometaplasia Mario T. Arguelles, N.D.,” Jun.% B. Viloria., Jr., nl.D., F.R..C.P.(C),“” and Thomas P. UcCrory, D.D.S.,“““” Uccnuel C. Talew, M.D.,*** illmtreal, Quebec, Canada MONTREAL

GENERAL

HOSPITAL

AND

JEWISH

HOSPITAL

Three cases of necrotizing sialometaplasia of minor salivary glands are presented. Clinically and pathologically, this nonneoplxstic lesion of the palate can be easily mistaken for carcinoma. The main histologic features are localized infarction of minor salivary glands and extensive squamous metaplasia with retention of the lobular architecture of the involved glands. The possible etiologic factors arc discussed.

N

ecrotizing sialometaplasia is a benign inflammatory condition of minor salivary glands with clinical and histopathologic features that simulate mucoepidermoid tumors and squamous-cell carcinoma. The initial report of seven cases of this entity was by Abrams and associates1 in 1973, and Dunlap and Barker2 presented five additional cases in 1974. Both publications emphasized that necrotizing sialometaplasia may be misinterpreted as malignant and the patient treated by an unnecessarily aggressive surgical procedure. This study reports the clinical and histologic features of three additional cases of necrotizing sialometaplasia. All were successfully treated by local surgical resection. The morphologic features that distinguish this lesion from malignant tumors will be emphasized, and possible etiologic factors will be discussed. CASE REPORTS CASE 1

A 33.yrar-old Caucasian woman presented in August, 1973, with the sudden onset of sharp pain and numbness in the left hard palate. The pain radiated to the left forehead and mandible and was associated with swelling of the left rheek. The patient denied smoking and did not drink excessively. Thero was no history of trauma prrceding the *Resident in Pathology, Montreal General Hospital. **Assistant Pathologist, Montreal General Hospital. ***Resident in Pathology, Jewish General Hospital. ****Assistant Dentist, Montreal General Hospital.

86

Pig. I. Mucous glands amous cells. (Hcmatoxylin

and excretory duct epithelium and eosin stain. Magnification,

replaced x240.)

by cytologically

symptoms. On examination, a firm, nonmobile 0.5 cm. mass was present in the posterior third of the left hard palate. There was decreased sensation to a pin prick around the alveolar margin of the anterior two thirds of the left palate. The localized pain and numbness function was were thought to bc due to invasion of tumor around the nerves. Palatine normal. An incisional biopsy of the lesion was interpreted as a well-differentiated mucoepidermoid tumor of a minor salivary gland. A wide local resection of the tumor was performed. CASE 2

A 53.year-old Caucasian man was admitted in May, 1974, after noticing a painful lesion in the palate. This man was a heavy smoker but denied :~lcohol intake. There was no history of trauma, and the patient was not on medication. The lesion was located in the left hard palate; it nwasurcd 1.0 cm. in diameter, had rolled borders, and vas centrally ulccrnted. The clinical impression was that this was a carcinoma. An excisional biopsy was reported as ~~-ell-differenti:\tcd epidermoid carcinoma with superficial invasion. Radical surgery \V:LS contemplated, but after a review of the slides the diagnosis was revised ant1 no further treatment was gioen. CASE 3

A 49.year-old Caucasian man was seen lump in the palate. He was a heavy smoker trauma or drug intake. On examination, the painful, ulcerated, and measured 3.0 cm. in the diagnosis was nrcrotizing sialomrtaplasia PATHOLQGIC Gross

in the Dental Clinic in October, 1974, with n and drank moderately. There was no history of lesion was in the right hard palate. It was firm, diameter. Incisional biopsy was performed, and of minor salivary glands.

FINDINGS

examination

All three lesions were located in the hard palate. In Case 1 there was a nonulcerated elevated lesion, while in Cases 2 and 3 there were ulcers, one with rolled borders.

88

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et cd.

Ornl Surg. .Jdj-,

1976

Fig. 8. Hetnined lobular architecture of infarcted minor salivary glands. Nests of metaplastic squamous cells are noted in one part of the lobule. (Hematoxylin rind rosin stain. Jlagnification, x20.)

Microscopic

examination

Histologic features were similar in all the lesions. The epithelium adjacent to the ulcers and the intact cpithelium in Case 1 showed hyperkeratosis and marked pseudoepitheliomatous hyperplasia. The squamous cells, however, were cytologically bland, with intercellular bridges and only occasional normal mitoses. The excretory ducts of the infarcted minor salivary glands showed extensive squamous metaplasia of their lining epithelium, in some areas several cells thick, which was continuous with the overlying hyperplastic epithelium, giving the impression of squamous-cell carcinoma of surface origin with invasion of the gland (Fig. 1). Occasionally, salivary gland ducts showed transition of lining epithelium from mucus-secreting columnar cells to stratified squamous cells simulating mucoepidermoid carcinoma. The underlying minor salivary gland tissue showed extensive infarction. The necrotic lobules and remnants of acinar tissue were borderd by slightly edematous fibrovascular connective tissue that was infiltrated by acute and chronic inflammatory cells. In a few areas, mucus had extravasated into thr adjacent parenchyma, where occasional reactions of the foreign body type were not,ed. In spite of the extensive necrosis and inflammatory and metaplastic changes, the lobular architecture of the salivary gland was still preserved (Fig. 2)) as best demonstrated with reticulin stain. The blood vessels in the stroma showed marked narrowing of their lumina as a result of proliferation of intimal and smooth muscle cells. There was no thrombotic occlusion of these vessels. DISCUSSION

Necrotizing sialometaplasia is an uncommon condition. The three cases in this study bring the total reported cases to fifteen. The tern1 ?~ecroti&g sinlo-

Trauma

(physical,

chemical,

etc.)

Infection \ Localized

Vascular

swelling

iniury

I

Trauma Localized vasculitis Atherosclerosis Chemical, physical,

etc,

/ Vascular spasm and/or thrombosis ___\\\

/ Compromised blood

supply

1

Infarction

1 Ulceration

i Repair

Diagram 1.

metnplnsiu. is a most appropriate designation for this condition and is descriptive of the lobular necrosis and ductal and glandular metaplasia. The salivary gland lobules are necrotic, and there is extensive squamous mctaplasia of the duct epithelium extending from the intramucosal portion well into t,he lobules. This pattern simulates that of invasive squamous-cell carcinoma of mucosal origin. On a cytologic basis, however, the squamous cpitheliam appears benign. In spite of the severe mctaplastic and inflammatory changes, the general lobular architecture is maintained; this is the most important criterion for the diagnosis of necrotizing sialometaplasia. It is, therefore, of great importance that diagnosis be based upon either excisional or generous incisional biopsy that includes generous amounts of the underlying salivary gland tissue. With a confident tissue diagnosis of necrotizing sialometaplasia, further treatment is not required. In Case 1 a wide excision of the lesion was pcrformed, and no recurrence was noted in 17 months. In the remaining two cases incisional biopsies were performed, and the patients arc free of disease after intervals of 8 and 3 months. The lesions healed spontaneously. The cause of nccrotizing sialometaplasia is still unclear. Since the basic lesion is an infarct with subsequent ulceration and repair, it is most likely that this is brought about by an inadequate blood supply. The arterial supply of the minor salivary glands is the anterior palatine artcry that, enters the oral cavity through a rigid foramen in the hard palate, the major palatine foramen. The main branches course anterolaterally with only small branches passing medially to the anatomic areas where nccrotizing sialometaplasia has been

90

flrguelles

et 01.

described. Any agent-physical, chemical, or infectious-that can cause swelling around the major palatine foramen Ina)- compromise the blood supply and lead to ischemic necrosis. These and other possible ctiologic factors arc shown in Diagram 1. Attempt at repair is c~spncsscd by squan~ons mctaplasin and rcepithelization of the ulcerated area. The great danger in misdiagnosing this condition is misappreciation an(l lack of knowledge of the existence of this nonneoplastic lesion. The authors the manuscript.

wish to express

their

thanks

to Dr.

M. E. Kirk

for

her critical

review

of

REFERENCES

1. Abmms, A. M., Melrose, R. J., and Howell, F. V.: Necrotizing Sialometnplnsia, Cancer 32: 130.135, 1973. Sialometaplasia, ORAL SITRG. 37: 722-727, 2. Dunlap, C. L., and Barker, B. F.: Nccrotizing 1974.

Reprint requests to: Dr. Juan B. Viloria, Jr. Pathology Department Montreal General Hospital 1650 Cedar Are. Montreal, Quebec, Canada