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. 2022 Jul-Sep;63(3):545-553.
doi: 10.47162/RJME.63.3.09.

Subgemmal neurogenous plaques of the tongue: a systematic autopsy study

José Fernando Val-Bernal  1 , María Francisca Garijo, Natalia Fontanil
Affiliations

Subgemmal neurogenous plaques of the tongue: a systematic autopsy study

José Fernando Val-Bernal et al. Rom J Morphol Embryol. 2022 Jul-Sep.

Abstract

Subgemmal neurogenous plaque (SNP) is a subepithelial nerve plexus associated with taste buds, occasionally observed in tongue biopsies. There is no evaluation of the prevalence of this structure in the general population. We present a systematic study of samples obtained at random from the dorsal portion of the oral tongue in 205 consecutive complete autopsies. Each sample was about 15 mm long and 10 mm thick. Four hundred fifty-eight samples were routinely obtained and an average of 2.23±0.88 samples per case (range 1-7) was collected. The total number of SNPs observed was 556, with a mean of 2.71±2.68 per case (range 0-16). This means that for every 15 linear mm of the oral tongue, approximately 2.7 SNPs can be present. SNPs display several ages, and they do not show sex differences. The mean size of these structures was 2.1±0.94 mm (range 0.6-3.6 mm). SNP is characterized by its unique neural, zonal pattern with a superficial neurofibroma-like area and a deeper neuroma-like area. Special features of the SNPs include the presence of taste buds (49.1%), ganglion cells (26.3%), dilated thin-walled vessels (11.3%), salivary gland excretory ducts emptying on the surface of the papillae (6.1%), moderate-severe inflammatory infiltrate (6.8%), presence of lymphoid tissue in the vicinity (7.0%), and hyperplasia of the epithelial cover with pseudoepitheliomatous appearance (7.0%). The differential diagnoses include schwannoma, neurofibroma, ganglioneuroma, traumatic neuroma, mucosal neuroma, and squamous cell carcinoma. SNPs are small, normal structures that may undergo hyperplasia and are usually seen incidentally.

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Conflict of interest statement

The authors declare that they have no conflict of interests.

Figures

Figure 1
Figure 1
Taste buds in the SNPs: (A) Taste buds are visible in a plaque covering the epithelium; (B) Continuity of the SNP with the taste buds can be seen. HE staining: (A) ×200. S100 protein immunostaining: (B) ×100. HE: Hematoxylin–Eosin; SNP: Subgemmal neurogenous plaque.
Figure 2
Figure 2
Complete SNP showing a biphasic pattern. The arrow points to a ganglion cell. HE staining, ×100.
Figure 3
Figure 3
The base of the plaque is composed of small nerve fascicles intermingled with ganglion cells (arrows). S100 immunostaining, ×200.
Figure 4
Figure 4
Superficial component of a cellular SNP showing elongated, wavy cells in a predominant vertical arrangement. HE staining, ×200.
Figure 5
Figure 5
Superficial component of the SNP with individual, elongated, wavy cells parallel to the surface. HE staining, ×200.
Figure 6
Figure 6
Elongated cells recognizable as Schwann cells organized as individualized elements parallel to the surface. S100 protein immunostaining, ×400.
Figure 7
Figure 7
Schwann cells form twisted and intertwined cords. S100 protein immunostaining, ×200.
Figure 8
Figure 8
(A) Axons are combined with the Schwann cells. (B) The Schwann cell/axon ratio is about the same. NF protein immunostaining: (A) ×200; (B) ×400. NF: Neurofilament.
Figure 9
Figure 9
CD34-positive endoneurial fibroblasts are shown in the nerve fascicles at the base of the plaque. Anti-CD34 antibody immunostaining, ×200. CD34: Cluster of differentiation 34.
Figure 10
Figure 10
Low cell density plaque showing vascular ectasia. HE staining, ×200.
Figure 11
Figure 11
Nerve fascicles of the deeper zone are showing a thin perineurium positive for EMA. Anti-EMA antibody immunostaining, ×200. EMA: Epithelial membrane antigen.
Figure 12
Figure 12
Hyperplasia of the nerve fascicles with the presence of ganglion cells in the depth of the plaque. S100 protein immunostaining, ×200.
Figure 13
Figure 13
Salivary excretory duct with squamous metaplasia emptying into the surface of the plaque. HE staining, ×200
Figure 14
Figure 14
Lymphoid tissue in the vicinity of a plaque. S100 protein immunostaining, ×200.
Figure 15
Figure 15
Adjacent SNPs: (A) Two contiguous plaques are separated by the cleft of a papilla; (B) Two symmetrical mirror plaques. S100 protein immunostaining: (A and B) ×100.
Figure 16
Figure 16
Pseudoepitheliomatous hyperplasia in an SNP. HE staining, ×100.
Figure 17
Figure 17
Pseudoepitheliomatous hyperplasia associated with the neural component of the plaque. S100 protein immunostaining, ×100.
Figure 18
Figure 18
Pseudoepitheliomatous hyperplasia: (A) Squamous nests with acidophilic cells are often surrounded by basal cells; (B) Squamous nests are constituted by cells with well-defined limits. HE staining: (A and B) ×200.
Figure 19
Figure 19
Pseudoepitheliomatous hyperplasia with predominant basal cell nests. Some squamous nests show keratinization. HE staining, ×200.
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