J Oral Maxillofac Surg59:80-83, 2001

Leiomyoma of the Lip: Report of a Case

Giovanna Orsini, DDS,* Massimiliano Fioroni, DDS,†

Corrado Rubini, MD,‡ and Adriano Piattelli, MD, DDS§

Leiomyoma is the most common benign neoplasmof the uterus and stomach, but it is rare in the oralcavity. The first case of oral leiomyoma was re-ported by Blanc in 1884.1 Baden et al2 reviewed theliterature and found only 5 cases of oral leiomyomain a series of 7,748 leiomyomas from all sites. In thereview of the literature made by the latter authors,the lips were the most common oral site (27.46%),followed by the tongue (18.30%), cheeks and palate(15.49%), gingiva (8.45%), and mandible (5.63%).Other authors3 have reported the tongue, palate,

cheek, and lips as the most common intraoral sites.The tumor also has been reported in the gingiva,lower buccal sulcus, floor of the mouth, lowerlabial sulcus, salivary glands, uvula, central mandi-ble, and maxillary tooth socket.2 The greatest inci-dence is in the 40- to 59-year age-group.The appearance of the leiomyoma is generally a

nonulcerated, small (1 to 2 cm), painless, sessile mass,although several authors have reported painful le-sions.4 Leiomyoma has been divided into 3 types inthe World Health Organization classification2:leiomyomas (solid), angiomyomas (vascular leiomyo-mas), and epithelioid leiomyomas (leiomyoblastoma).The solid and vascular types were the most frequentvariants.5 Recently, leiomyomas located in unusualoral sites (mandible, zygomatic bone) have been re-ported.5-7 We report a case of leiomyoma microscop-ically characterized by a local infiltrative growth thatcould have been misdiagnosed as a malignant neo-plasm.

Report of Case

A 59-year-old patient was seen in our Department for apainless mass located in the right upper lip measuringapproximately 0.8 cm in diameter (Fig 1). The lesion washard and had indurated margins. The regional lymph nodeswere not enlarged.

*Research Fellow, Dental School, University of Chieti, Italy.

†Research Fellow, Dental School, University of Ancona, Italy.

‡Researcher, Institute of Pathologic Anatomy and Histopathol-

ogy, University of Ancona, Italy.

§Professor of Oral Medicine and Pathology, Dental School, Uni-

versity of Chieti, Italy.

Supported in part by the National Research Council (C.N.R.),

Rome, Italy, and by the Ministry of University, Research, Science

and Technology (M.U.R.S.T.), Rome, Italy.

Address correspondence and reprint requests to Dr Piattelli: Via

F. Sciucchi 63, 66100 Chieti, Italy; e-mail: apiattelli@unich.it

© 2001 American Association of Oral and Maxillofacial Surgeons

0278-2391/01/5901-0015$3.00/0

doi:10.1053/joms.2001.19299

80 LEIOMYOMA OF THE LIP

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Under local anesthesia, the lesion was excised, and micro-scopic examination showed proliferating smooth muscle cellsthat appeared to infiltrate the residual striated muscle cells (Fig2). The tumor was composed of spindle cells, with typicallyelongated nuclei, dispersed in fascicles; adipose tissue wasfound in the periphery of the lesion (Fig 3). Muscle-specificactin antigen positivity for smooth muscle cells and smallvessels was observed (Fig 4). However, no atypia or mitoticfigures were observed. The final diagnosis was leiomyoma. Norecurrence has been observed after a 5-year follow-up.

DiscussionBecause of the scarcity of smooth muscle in the oral

cavity, the leiomyoma is a relatively uncommon lesion in

that location. When found in the oral mucosa, theleiomyoma most commonly affects the lips. The nextmost frequent sites are the palate, tongue, and buccalmucosa.8 The tumor generally does not cause pain andis noted only as a mass. It is a slow-growing, well-defined, movable tumor that sometimes is peduncu-lated. The color of the leiomyoma varies from bluish toreddish, depending on the number of blood vesselspresent.9

Sources of smooth muscle in the oral cavity areblood vessels,10 circumvallate papillae, and hetero-topic smooth muscle.11 Duhig and Ayer12 suggestedthat vascular leiomyomas may represent only onestage in a continuous process of smooth muscle pro-liferation, and an appreciable number may be vascularmalformations. The sequence of progression that theysuggest is hemangioma, angioma, vascular leiomy-oma, leiomyoma, and solid leiomyoma.13

A division of 142 oral leiomyomas2 into the clas-sic 3 subtypes, solid leiomyoma, vascular leiomy-oma, and epithelioid leiomyoma, clearly showedthe predominance of vascular leiomyoma (angio-myoma), with 94 cases. Solid leiomyoma was nextin frequency with 45 cases, and there were only 2cases of epithelioid leiomyoma. The prognosis oforal leiomyomas is excellent, and surgical excisionis curative. Recurrence is rare.Leiomyoma can be confused with fibroma, neu-

rofibroma, and low-grade fibrosarcoma.14 Someleiomyomas might be difficult to differentiate fromthe malignant leiomyosarcoma; the number of mitoticfigures, anaplasia, and bizarre cell forms are consid-

FIGURE 1. Clinical view of the lesion of the lip.

FIGURE 2. The tumor is com-posed of spindle cells betweenwhich there are normal striatedmuscle cells (arrow). (Hematoxy-lin and eosin, original magnifica-tion �10.)

ORSINI ET AL 81

ered the features that can help in predicting thedegree of malignancy.3 Most investigators agree that iffewer than 5 mitoses per 20 high-power fields arefound, the prognosis is generally good, but that theprognosis worsens progressively as more mitoses be-came apparent. However, the use of only mitoticfigure counts for the distinction of benign from ma-lignant lesions is not always reliable.10 There are nu-merous reports in the literature of smooth muscletumors that did not show frequent mitotic figures butinvaded locally or metastasized to lymph nodes.14

Microscopic diagnosis might occasionally be difficultbecause the spindle cell proliferation has many similar-ities with neurofibroma, schwannoma, and fibromato-sis.15 Special stains that identify collagen might behelpful in distinguishing these lesions. Ultrastruc-tural demonstration of myofilaments and immunohisto-chemical staining of desmin-type intermediate filamentsor actin and myosin antigens also can be useful in estab-lishing a definitive diagnosis. Conversely, the vascularleiomyoma has numerous thick-walled vessels associ-ated with well-differentiated smooth muscle cells.15

FIGURE 3. The tumor is com-posed of spindle cells arrangedin fascicles. Between them arecollagen fibers. Small vesselsalso are present. Adipose tissueis seen in the periphery of thelesion (arrow). (Hematoxylin andeosin, original magnification�10.)

FIGURE 4. Positivity of thesmooth muscle cells for muscle-specific actin and negativity ofthe striated muscle cells are seenin the upper part of the section.On the lower part, muscle-spe-cific actin positivity is observed inthe vascular components (arrow).(Peroxidase-antiperoxidase stainfor muscle-specific actin, originalmagnification �10.)

82 LEIOMYOMA OF THE LIP

The clinical differential diagnosis of leiomyoma of thelip has to include other benign proliferations such asfocal epithelial hyperplasia, rhabdomyoma, fibroma,neurofibroma, lipoma, schwannoma, pyogenic granu-loma, and mucocele.16 Pyogenic granuloma bleeds eas-ily and grows rapidly and is rarely located on the lips.Mucocele is a dome-shaped, bluish, translucent, fluctu-ant swelling.17 The differential diagnosis from a salivarygland tumor, usually a pleomorphic adenoma, is madeby using immunohistochemical findings.18 Malignantneoplasms that can be mistaken for leiomyoma areleiomyosarcoma, fibrosarcoma, and rhabdomyosarco-ma.19 As seen in this case, immunohistochemistry is avaluable, precise, and reliable method for establishing adefinitive diagnosis of oral leiomyoma and, in particular,for the differential diagnosis of spindle-cell neoplasmsarising in the oral cavity.

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