C A S E R E P O R T
Solitary pigmentation of the tongue: lentigo simplex or pigmented fungiform papilla?
C. McCarthy1, D. Holt1& A. Triantafyllou2
1Oral Medicine, Liverpool University Dental Hospital, Liverpool, UK
2Oral & Maxillofacial Pathology, School of Dentistry, University of Liverpool & Pathology Department, Liverpool Clinical Laboratories, Liverpool, UK
Key words:
fungiform papillae, histopathology, lentigo simplex, melanocytes, pigmentation, tongue
Correspondence to:
Dr A Triantafyllou
Oral & Maxillofacial Pathology Liverpool University Dental Hospital Liverpool L3 5PS
UK
Tel.: +44 151 706 5243 Fax: 0151-706 5131
email: A.Triantafyllou@liverpool.ac.uk
Accepted: 22 November 2016
doi:10.1111/ors.12264
Abstract
The report discusses a solitary pigmentation on the dorsal tongue of an adult female, featuring variably concentrated melanocytes, hyper- pigmened keratinocytes and pigmentary incontinence spatially related to fungiform and adjacent filiform papillae. Interpretations included lentigo simplex and pigmented fungiform papilla, and are critically discussed in conjunction with clinical considerations.
Introduction
While melanocytic naevi and melanotic macule of the oral mucosa are established1–4, little or no atten- tion has been paid to lesions of intermediate pathol- ogy therein. In addition, pigmented fungiform papillae of the tongue have been repeatedly explored by dermatologists5,6, but are not widely known among specialists in oral disease7. In this context, the following case of a solitary pigmentation of the tongue, which showed features reconcilable with pigmented fungiform papilla or lentigo simplex, a lesion possibly spanning the range between naevi and melanotic macule, is of interest.
Case report
A 32-year-old, Caucasian female presented to the Oral Medicine Clinic, complaining of a dark patch on the top of her tongue. The patient was 9 months post-partum at presentation, asymptomatic and gen- erally well. She had been aware of the patch for around 2–3 years and reported it had become more
noticeable during her pregnancy. The medical his- tory was unremarkable and the patient took no medications.
On clinical examination, an isolated 6.0 mm oval area of brown pigmentation was noted on the left dorsal surface of the tongue (Fig. 1). The area did not appear raised, had reasonably well-defined borders, did not blanch with pressure and was soft on palpation. The mucosal surface was intact, with no ulceration or contact bleeding. The patient reported no other areas of pigmentation on her body.
The clinical impression was of a melanotic macule.
An incisional biopsy under local anaesthesia was performed to establish a definite diagnosis. Healing was uneventful.
Histological examination of the routinely pre- served and processed material obtained during biopsy, showed lingual mucosa and underlying mus- culature. The former included a fungiform and a few filiform papillae. The stroma supporting the fungi- form and adjacent filiform papillae showed promi- nent melanophages (Fig. 2A) decorated on special
staining (Fig. 2B), which also accentuated variable hyperpigmentation of overlying deep keratinocytes (Fig. 2C). Immunohistochemistry for Melan-A and S-100 protein with the use of alkaline phosphatase instead of peroxidase revealed variable concentration of intraepithelial melanocytes in those areas (Fig. 2D). Melanocytes were not seen in adjacent surface epithelium/filiform papillae (Fig. 2E).
Discussion
The histological findings of hyperpigmentation of basal keratinocytes and melanophages in the lamina propria (pigmentary incontinence) are within the range of oral melanotic macule4. This would corre- spond with the clinical suspicion. However, melan- otic macules are rare (3.3%) on the tongue and lack increased melanocytic numbers4,8,9. Such an increase together with keratinocytic hyperpigmentation and pigmentary incontinence would tip the scales towards a diagnosis of lentigo simplex8–10. Increased melanocytes featured in the present case, particularly in terms of their localised concentration and absence from adjacent epithelium (Fig. 2D, E). Paucity or even absence of melanocytes from the human ton- gue has been reported, but is controversial (see Barrett and Scully for a review and references11).
Allowing for degrees of plausibility, the present findings may reflect lentigo simplex, their papillary spatial relationships being incidental to the concen- tration of fungiform papillae in the anterior tongue12 and widespread abundance of dorsal filiform papillae.
The alternative interpretation would be pigmented fungiform papilla of the tongue (PFPT). It has been noted that PFTP is not alien to the medical literature.
aspects and reported that, of 200 African-Americans examined, 30% of females and 25% of males showed PFPT; the corresponding percentages for 100 Caucasians were 2% and 0% respectively5. A later investigation of 14 346 Chinese dermatological out- patients recorded 58 (0.4%) PFPT cases (56 females and 2 males)6. Reports of PFPT in other ethnic groups, for instance African13, South Asian14,15, Brazilian16, Hispanic5,7, Indian17, Korean18 and Mid- dle Eastern19, are sporadic. Adibi et al. felt that the dearth of pertinent dental publications is remarkable, and proposed ‘papillary tip melanosis’ as a more appropriate term7. We share the feelings of those authors, but do not support changing terminology because of inevitable confusion. Holzwanger et al.
also suggested three clinical patterns of PFPT: type I refers to a single area of pigmentation, with cluster- ing of involved papillae; type II refers to the involve- ment of between three and seven papillae scattered around the tongue; and type III refers to the rare case in which all fungiform papillae are involved5. Type II was more common in the sample examined by those authors5, but the Chinese investigation indicated type I6. Our case could qualify as type I PFPT.
Before hailing the present clinicopathological pre- sentation as PFPT in a Caucasian, the following com- ments are deemed necessary. The rather diffuse background pigmentation in our case (Fig. 1) con- trasts with the ‘punctuate’ pattern in previously pub- lished clinical pictures of PFPT5–7, 13–19. This may be attributable to spreading of changes in an adjacent filiform papilla (Fig. 2B), a feature also noted by Adibi et al.7. Light-photomicrographs of PFPT have been published. They are usually focussing on mela- nophages in the lamina propria5–7, 18 and, occasion- ally, keratinocytic hyperpigmentation7. In contrast with our observations, melanocytes are ignored, though a ‘clear’ intraepithelial cell, possibly a mela- nocyte, is discernible in a photomicrograph given by Holzwanger et al.5.
The above interpretations are not mutually exclusive. Unless of ‘clear’ appearance, identifying and counting melanocytes is difficult in areas of keratinocytic hyperpigmentation. Likewise, con- ventional immunohistochemistry for melanocytic markers would be unhelpful as immunoperoxidase labelling yields brown reaction product indistinguish- able from melanin. On the other hand, immune- alkaline phosphatase procedures, as applied here, yield a red reaction product and reveal melanocytes in colour contrasting with melanin. This would allow
Figure 1 Lesion at presentation.
confident identification and together with resolving uncertainties about lingual melanocytes11, achieve a desirable terminological and conceptual precision.
Turning to aetiological considerations, sex hor- mones may have a role in the development of PFPT6. This is supported by the increased occurrence of PFPT in females5,6, and its association with Hori’s nevus and melasma, which express higher levels of oestrogen receptors6. Isolated observations also sug- gest a drug-induced mechanism7. Interestingly, our
patient noticed the lesion became more prominent during pregnancy, and was not on medication. The suggestions do not, however, explain the spatial rela- tionship between incontinent melanocytes20 and fungiform papilla, which is illustrated in Fig. 2E.
That this may be incidental has been discussed, but speculation over biological events is tempting. Fungi- form papillae in mammals are richly innervated, and possibly depend on species-related, trophic influ- ences of the chorda tympani, lingual nerve and C
B
◄
A
M
*
1 2 3 4
5
D Ep
E
Ep
*
1
Figure 2 (A) Scanning view of section stained with haematoxylin and eosin (objective magnification9 2) shows fungiform (asterisk) and at least five filiform papillae (1–5); pigmented elements in papillary stroma are arrowed and confined to an area that measured 0.6 mm in length and corre- sponds to the linear segment; M, skeletal muscle. (B) Adjacent section stained with Masson–Fontana; pigmented elements staining black are more prominent subepithelially (objective magnification 94). The rectangled area is magnified in (C); staining is associated with stromal melanophages and melanin-laden keratinocytes (arrowhead) (objective magnification910). (D) Dendritic basal melanocytes staining red, concentrate at tips of epithelial (Ep) rete; melanophages (arrows) are unstained (Melan-A, objective magnification920). (E). Scanning view of immunohistochemically trea- ted section shows localisation of stained melanocytes in the fungiform (asterisk) and contiguous filiform (1) papillae, whereas adjacent epithelium (Ep) and melanophages (arrow) are unstained (compare with Fig. 2A) (Melan-A, objective magnification92).
nance . Traditional views do not favour a relation between melanocytes and innervation, but nerve branches are present in dermal papillae and the over- lying epidermis accommodates melanocytes20.
The aforementioned Chinese investigation found that 76% of individuals with PFPT were in the 2nd or 3rd decades, age ranging from 4 to 83 years6. The wide age range together with a possible hormonal dependence and benign nature of PFPT are similar to patterns of physiological oral pigmentation7. Accord- ingly, no treatment is necessary and confident clini- cal recognition should preclude biopsy7. In this vein, dermoscopy has recently drawn attention15,29,30, though should be probably reserved for type II and III lesions. We would advise biopsy for type I lesions of diffuse rather than punctuate pigmentation.
It is hoped that the present report highlights clini- copathological presentations frustratingly ignored in the dental literature, and the approach to various interpretations, although largely academic, would increase understanding and diagnostic skills.
Conflicts of interest
The authors have stated explicitly that there are no conflicts of interest in connection with this article.
Funding
None.
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