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Nevus Trichilemmocysticus

A Mild Case

Faria Sanchez, Paula Cristina MD; Sakai Valente, Neusa Yuriko MD; Simonsen Nico, Marcello Menta MD

The American Journal of Dermatopathology: September 2019 - Volume 41 - Issue 9 - p 692–694
doi: 10.1097/DAD.0000000000001196
Letters to the Editor

Department of Dermatology, Medical School, University of São Paulo, São Paulo, Brazil

The authors declare no conflicts of interest.

To the Editor:

Nevus trichilemmocysticus (NTC) is a recently described type of organoid epidermal nevus; only a few have been identified and reported.1–6 NTC is characterized by multiple follicular filiform hyperkeratoses and trichilemmal cysts in a Blaschkoid distribution. Most cases described involve extensive areas of the skin and present with disfiguring lesions. This report refers to a case of NTC affecting a small cutaneous segment. This is the mildest case of NTC reported so far.

A 29-year-old Brazilian woman reported a congenital lesion on the trunk. On examination, there were many superficial and deep cystic papules and nodules ranging from 2 to 10 mm intermingled with tiny hyperkeratotic spikes; lesions were grouped forming a segmental band affecting the left side of the thorax (Figs. 1A, B). On the left hand, there was a linear hyperkeratotic band with yellowish horny plugs and accentuation of dermatoglyphics that extended from the palm to the fourth and fifth fingers (Figs. 1C, D).



Histopathology of a nodular lesion revealed a trichilemmal cyst (Figs. 2A, B); histopathology of the filiform keratotic papule revealed a hyperkeratotic plug in a dilated follicle with trichilemmal differentiation (Figs. 2C, D); the palmar keratotic lesions showed only slight acanthosis and hyperkeratosis in comparison with normal skin.



Epithelial nevi are segmental malformations resulting from postzygotic mutations.7 They are classified as nonorganoid (epidermal nevus, epidermolytic epidermal nevus, and nevus CHILD) and organoid (sebaceous nevus, nevus comedonicus, porokeratotic eccrine ostial duct nevus).7–9

In 2007, Tanctcheva-Poor et al1 described a new organoid nevus, which they named “nevus trichilemmocysticus.” Lesions include comedo-like plugs and filiform hyperkeratosis associated with trichilemmal cysts in arrangements that follow lines of Blaschko.1,2 On histopathology, there was epidermal acanthosis with deep invaginations filled with massive orthokeratosis, parakeratotic columns, and an absent granular layer (isthmic or trichilemmal differentiation)1–3; keratosis in sebaceous ducts and acrosyringia has also been observed.3 Histopathology of the nodules is typical of trichilemmal cysts, where the cyst wall shows a flat stratified epithelium with abrupt keratinization without the presence of a granular layer. A coexistence with bone lesions has been described in what can be considered a distinct epidermal nevus syndrome.1,4

Besides the mild intensity of the present case when compared with the previously described cases of NTC, an interesting aspect includes the presence of palmar involvement; the biopsy of such lesion showed only acanthosis and hyperkeratosis, similarly to 2 previously described, more severe cases.2,5 No eccrine changes were observed. Prominent eccrine glands next to filiform hyperkeratosis were found in lesions located on the dorsum of a finger.3

Eiberg et al10 in 2005 studied 38 members of a family and mapped the gene TRICY1 whose mutation on chromosome band 3p24-p21.2 is related to trichilemmal cysts as an autosomal dominant trait. However, this type of mutation, despite explaining the occurrence of trichilemmal cyst, does not justify the other clinical findings present in NTC. New studies about the genetic mechanisms that may explain this malformation are necessary.

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