Amalgam tattoo of the oral mucosa mimics malignant melanoma
Article first published online: 20 SEP 2010
© 2010 Japanese Dermatological Association
The Journal of Dermatology
Special Issue: SPECIAL ISSUE: Dermoscopy (pages 1-75)
Volume 38, Issue 1, pages 101–103, January 2011
How to Cite
AMANO, H., TAMURA, A., YASUDA, M., YAMANAKA, M., TAKEUCHI, Y., SASAOKA, K., YOKOO, S. and ISHIKAWA, O. (2011), Amalgam tattoo of the oral mucosa mimics malignant melanoma. The Journal of Dermatology, 38: 101–103. doi: 10.1111/j.1346-8138.2010.01007.x
- Issue published online: 22 DEC 2010
- Article first published online: 20 SEP 2010
Amalgam pigmentation, generally called amalgam tattoo, is a pigmented lesion on the oral mucosa.1 Amalgam is the most commonly used dental restorative material for dental fillings because it is inexpensive and relatively easy to manipulate during placement. Amalgam is characterized by its initial pliability and it can be easily packed to fill any irregular space. It then forms a hard, durable compound with bacteriostatic effects. Amalgam fillings are made of a mixture of several metallic particles, especially mercury, silver and tin.
Clinically, amalgam tattoos appear as blue, black or dark gray asymptomatic, flat macules on the oral mucosa, located adjacent to a restored tooth, most commonly on the gingival surfaces.1,2 A pigmented mucosal lesion requires an extensive differential diagnosis, particularly with malignant melanoma.
A 63-year-old woman had received treatment to her teeth many years ago. When she received dental scaling 2 months prior, an asymptomatic pigmented lesion on the oral mucosa was pointed out by a dentist. Over the next 2 months, the lesion considerably enhanced. She was referred for evaluation of an asymptomatic pigmented lesion on the oral mucosa. Physical examination revealed a 9 mm × 6 mm blue-black macule, with irregular borders on the left floor of the mouth (Fig. 1). Regional lymphadenopathy was not noted. Adjacent to the pigmented lesion, a tooth restored with a dental filling was confirmed (Fig. 1). The results of routine laboratory tests including hematology, liver and renal functions as well as C-reactive protein levels were within normal limits.
X-rays did not show the presence of metallic particles in the mucosa. With the main differential diagnoses of malignant melanoma and amalgam tattoo, the lesion was completely excised.
Histological studies revealed numerous fine granular, dark brown deposits in addition to irregular black fragments distributed among collagen fibers in the proper mucosa (Fig. 2). There were cleft-like spaces around the irregular black fragments. Chronic inflammatory infiltrates, mainly composed of lymphoid cells and plasma cells but not multinucleated foreign body giant cells, were noted surrounding the pigmented lesion and around the salivary glands just beneath the lesion; however, there were few inflammatory infiltrates within the pigmented lesion. No malignant cells were seen. The pigmented granules were negative to both Fontana–Masson and iron stains. The diagnosis of amalgam tattoo was established.
Amalgam tattoo is an iatrogenic lesion that follows the (traumatic) implantation of dental amalgam particles into soft tissue1–3 and the most common cause of exogenous pigmentation of the oral mucosa.4,5 Amalgam tattoos occur when small particles of the amalgam are inadvertently implanted into oral soft tissues during dental procedures. Alternatively, they can be caused by mercury and other metals directly penetrating into the soft tissues.2,3 Mercury amalgam used to build up endodontically treated teeth with a full gold-based crown may release very high levels of metals.
Clinically, amalgam tattoos appear as asymptomatic black, blue or gray macules, which are frequently seen on the gingiva, alveolar, buccal mucosa or floor of the oral cavity. The mucobuccal fold, palate and tongue may also be involved.1 The mandibular region is more frequently affected than the maxillar region. Approximately 5–6% of all cases consist of multiple lesions. Most lesions are 0.1–0.3 cm, and one-third are 0.4–0.6 cm in diameter at their widest point.1 The lesion in our case was 0.9 cm, which is larger than most lesions previously reported.
The amalgam tattoo should be differentiated from other pigmented lesions such as melanocytic nevus, focal melanosis, physical pigmentation, thrombosed varix, malignant melanoma and implanted exogenous materials. X-rays are recommended to confirm the presence of metallic particles. When gross fragments of amalgam are present in the tissue, X-rays are diagnostic.5 However, these particles are often too small or too widely dispersed to be visible on X-rays, so negative radiographic findings cannot rule out the diagnosis of amalgam tattoo. When there is no radiographic evidence or an adjacent restored tooth, histological examination is required to rule out other pigmented mucosal lesions, especially malignant melanoma.
In our case, the amalgam was present in the tissues as discrete, fine, dark granules, and as irregular solid fragments. Histological examination shows amalgam tattoos are composed of dark granules and solid fragments between collagen fibers and around vessels. On microscopic examination, there are two kinds of amalgam tattoo lesions: irregular, dark solid fragments of metals or numerous, discrete, fine brown or black granules dispersed between collagen bundles and around small blood vessels and nerves.1 In most lesions, both forms coexist. Buchner et al.1 analyzed 268 cases of amalgam tattoo in detail and reported that in 45% of the cases there was no tissue reaction, in 17% there was a macrophagic reaction and in 8% there was a chronic inflammatory reaction, usually in the form of a foreign body granuloma or amalgam granuloma.
Ultrastructural analysis of these deposits shows the presence of fine silver salts that preferably stain reticulum fibers. Multinucleated foreign-body giant cells may also be noted. Dark field microscopy shows the silver granules, which present as brilliantly refractile white particles against a dark background and appear in greater numbers than when viewed with light microscopy.
Generally, amalgam tattoos are removed for cosmetic reasons. Q-switched ruby laser has been used with favorable results.6 However, it remains unclear whether amalgam tattoos in the oral mucosa can lead to complications.7 For example, an allergy to amalgam particles could lead to a systemic reaction. In fact, Weaver et al.8 reported a 33-year-old woman who had systemic symptoms such as weight loss, fatigue, sinusitis and headaches. She also complained of localized soreness and occasional swelling. In addition, burning mouth syndrome,9 and oral lichenoid lesions10 due to amalgam have been reported. In these cases, surgical excision is recommended followed by histological confirmation.
In conclusion, we report a case of this peculiar form of oral pigmentation that resembles malignant melanoma. Amalgam tattoo can often be easily identified clinically; however, it cannot be differentiated from other pigmented lesions, especially malignant melanoma. Although most cases are reported by oral surgeons, dermatologists should be aware of and pay attention to this condition.
- 5Pigmented lesions of the oral cavity. Dermatol Ther 2002; 15: 218–228., .