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\begin{document}

\title{A case of subungual onycholemmal cyst}



\author[1]{Toktam Safari Giv}%
\author[1]{Mahdiyeh Movahedi}%
\author[1]{Sahar Dadkhahfar}%
\author[1]{Farsad Biglari}%
\author[1]{Azadeh Rakhshan}%
\author[1]{Ghazal Mardani}%
\author[1]{Meisam Jafari Kafiabadi}%
\affil[1]{Shahid Beheshti University of Medical Sciences}%


\vspace{-1em}



  
  \date{May 18, 2024}


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\textbf{Introduction}

Subungual onycholemmal cysts (SOC) also known as subungual epidermoid
inclusion cyst is an uncommon nail abnormality which affect the dermis
of the nail bed. SOC has variable clinical presentations include
onychodystrophy, ridging, clubbing, thickening, pigmentation or even
appears normal (1). It can also mimic different nail malignancy such as
melanoma, SCC or glomus tumor (2). In this report we document a case of
unilateral second right finger nail onychodystrophy in 54-year-old man.

\textbf{Case presentation}

A 54-year-old taxi driver was referred to our orthopaedic department
with onychodystrophy on a nail of the second right finger from a year
before the current presentation. No history of recent trauma, pain, or
bleeding has been noted. On physical examination, onycholysis and
onychodystrophy of the right second nail were revealed. The lesion had
tenderness when it was compressed bilaterally.

Complete surgical excision of the nail was performed with local
anaesthesia (Figure 1). On surgery of the nail plate, a lesion measuring
10 \selectlanguage{ngerman}× 10 mm appeared within the nail bed. The histopathological
examination revealed a subungual onycholemmal cyst (Figure 2).

\textbf{Discussion}

SOCs are a rare, usually asymptomatic, nail abnormalities which are
diagnosed incidentally in the progress of investigating other diseases
like melanomas. Previous studies have described the possibility of an
association between SOC and trauma, clubbing, and subsequently cyst
formation. Clubbing can affect the dermis of the nail by fibroblast
proliferation which causes cyst formation. Age, sex, lesion site,
differential diagnosis (macroscopic and microscopic), underlying
diseases, and treatments are listed in Table 1 of previous cases in this
field.

SOCs may have different clinical presentations, including onycholysis,
onychodystrophy, pigmentation of the nail bed, ridging, and thickening.
It most commonly affects single digits, mainly thumbs and great
toenails, and pain is not uncommon (3).

The subungual epidermoid inclusions that Lewin first referred to as the
follicular microcysts of the nail bed are bulbous proliferations of the
extremities of rete ridges, occasionally with the development of
microcysts (4). These microcysts seldom lose their attachment to the
nail bed epithelium and appear superficially within the dermis. The
production of homogeneous keratin without a granular layer characterizes
the keratinization of this superficial epithelial inclusion. The cyst's
epithelium also mimics the follicular isthmus (4).

Onycholemmal is the new term that is being used in literature. It
depicts a specific type of subungual tumor with a pattern of
onycholemmal microcysts and trichilemmal keratinization (5). All of
these results point to the presence of vestiges of follicular units in
the nail bed epithelium. In contrast to palms and soles, the nail
epithelium is an invagination of the dorsal epidermis overlaying the
digit that includes a few hair germs, consistent with embryology. The
clinical presentation in our index case included onychodystrophy and
onycholysis on a nail of the second right finger with no history of
recent trauma, pain, or bleeding. Subungual melanomas and onycholemmal
carcinomas can mimic SOC presentations and nail bed biopsy is required
for appropriate diagnosis (2).

On histopathology, onycholemmal cysts originate from the nail bed
epithelium and are restored with eosinophilic keratin in the absence of
a granular layer. The follicular isthmus outer root sheath is homologous
to SOC and it is keratinized with no granular layer (6). The nail bed
biopsy with partial or total nail avulsion is required for appropriate
diagnosis.

The differential diagnosis of onycholemmal cyst include subungual
keratoacanthoma. squamous cell carcinoma (SCC), verrucous carcinoma
(VC), glumus tumor, subungual metastasis and onycholemmal carcinoma. The
characteristic histological findings can help the exact diagnosis of
these lesions.

There are no specific treatment recommendations (3). The biopsy from the
affected area revealed multiple free-lying cysts within the dermis of
the nail bed, and in the near region to the epithelium of the nail bed.
The cysts were lined by the stratified squamous epithelium with no
granular layer or any cellular atypia. The cysts included luminal
onycholemmal keratin (3).

This report highlighted the variable clinical presentations of subungual
onycholemmal cysts (SOC), which can mimic different nail malignancies,
including subungual melanomas and onycholemmal carcinomas. Early
diagnosis of SOC by nail biopsy can improve the treatment outcome.

\textbf{Acknowledgements}

We would like to thank the patient for the granting us permission to
publish this article.

\textbf{Author contributions}

Toktam Safari Giv: Writing-original draft; manuscript submission.

Mahdiyeh Movahedi: Conceptualization; data curation.

Sahar Dadkhahfar: Supervision; writing-review and editing.

Farsad Biglari: Data curation.

Azadeh Rakhshan: Pathology report; writing-review and editing.

Ghazal Mardani: Supervision.

Meisam Jafari Kafiabadi: Conceptualization; data curation;
writing-review and editing.

\textbf{Funding information}

No funding was received for this study.

\textbf{Conflict of interest statement}

The authors declare that they have no conflicts of interest.

\textbf{Consent}

Written informed consent was obtained from the patient for the
publication of this case report and the accompanying images.



\textbf{References}

1. Telang GH, Jellinek N. Multiple calcified subungual epidermoid
inclusions. Journal of the American Academy of Dermatology.
2007;56(2):336-9.

2. Busquets J, Banala M, Campanelli C, Sahu J, Lee JB. Subungual
onycholemmal cyst of the toenail mimicking subungual melanoma. Cutis.
2016;98(2):107-10.

3. Lydrup E, Pedersen Pilt A, Schmidt VJ, Trøstrup H. Subungual
Onycholemmal Cysts: A Case Report. Case reports in dermatology.
2021;13(2):394-8.

4. LEWIN K. Subungual epidermoid inclusions. British Journal of
Dermatology. 1969;81(9):671-5.

5. Hurt MA, Weedon D. Weedon D. Weedon's Skin Pathology. 3rd ed. London:
Churchill Livingstone Elsevier, 2010: Dermatol Pract Concept. 2012 Jan
31;2(1):79-82. doi: 10.5826/dpc.0201a15.. eCollection 2012 Jan.

6. Alessi E, Coggi A, Gianotti R, Parafioriti A, Berti E. Onycholemmal
carcinoma. The American Journal of dermatopathology. 2004;26(5):397-402.

7. Rashid RM, Cutlan JE. Onycholemmal carcinoma. Dermatology online
journal. 2010;16(3):12.

8. Inaoki M, Makino E, Adachi M, Fujimoto W. Onycholemmal carcinoma.
Journal of cutaneous pathology. 2006;33(8):577-80.

9. Olvera-Rodríguez V, Toussaint-Caire S, Domínguez-Cherit J.
Onycholemmal Horn: An Exceedingly Rare Subungual Tumor. Skin appendage
disorders. 2021;7(5):413-7.

10. Han B, Lee CH, Han TY, Lee JH, Son SJ. A Case of Onycholemmal
Carcinoma in a 77-Year-Old Man. The American Journal of
dermatopathology. 2017;39(11):874-5.

Table 1: Age, sex, lesion site, differential diagnosis (macroscopic and
microscopic), underlying diseases, and treatments of previous cases\selectlanguage{english}
\begin{longtable}[]{@{}llllllll@{}}
\toprule
\begin{minipage}[b]{0.12\columnwidth}\raggedright\strut
Patient No\strut
\end{minipage} & \begin{minipage}[b]{0.12\columnwidth}\raggedright\strut
Age(years)/ Sex\strut
\end{minipage} & \begin{minipage}[b]{0.12\columnwidth}\raggedright\strut
Location\strut
\end{minipage} & \begin{minipage}[b]{0.12\columnwidth}\raggedright\strut
Clinical differential diagnosis\strut
\end{minipage} & \begin{minipage}[b]{0.12\columnwidth}\raggedright\strut
Histopathological differential diagnosis\strut
\end{minipage} & \begin{minipage}[b]{0.12\columnwidth}\raggedright\strut
Underlying condition\strut
\end{minipage} & \begin{minipage}[b]{0.12\columnwidth}\raggedright\strut
Treatment\strut
\end{minipage} & \begin{minipage}[b]{0.12\columnwidth}\raggedright\strut
First author reference number\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Case 1\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
73/female\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Left thumb nail\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Infection\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Invasive carcinoma with onycholemmal features.\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Diabetes and hypertension History of working in farm/ field\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Distal digital amputation\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Rashid (7)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Case 2\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
45/female\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Great toenail\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Subungual melanoma\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Subungual onycholemmal cyst\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Nail trauma in childhood\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Secondary intention with moist wound treatment\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Lydrup (3)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Case 3\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
23/female\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Right great toenail\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Subungual malignant melanoma\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Subungual onycholemmal cyst\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
5-year pigmentation of nail with no clear underlying condition\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Secondary intention\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Busquets (2)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Case 4\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
70/male\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Little finger of the right hand\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
SCC of the nail bed\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Onycholemmal carcinoma\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Not mentioned\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Resection of tumor and diarticulation of distal phalanx\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Inaoki (8)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Case 5\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
72/female\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Left thumb nail\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Bowen's disease SCC Proliferating onycholemmal tumor Wart/subungual
exostosis\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Onycholemmal horn\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
None\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Surgical resection\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Rodriguez (9)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Case 6\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
69/male\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Nail bed of fifth right finger\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Not mentioned\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Malignant proliferating onycholemmal cyst\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
None\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Amputation and disarticulation of involved phalanx\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Alessi (6)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Case 7\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
77/male\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
left second finger\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
SCC Metastatice carcinoma BCC\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Primary onycholemmal carcinoma\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
stage-4 non-small cell lung cancer/4-year history of slow-growing mass
on left second finger\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Involved nail amputation\strut
\end{minipage} & \begin{minipage}[t]{0.12\columnwidth}\raggedright\strut
Han (10)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Case 8\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
73/female\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Right great toenail\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Onychomycocis Trauma / Psoriasis/ Lichen planus\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Calcified subungual epidermoid inclusion\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
7-year thickening of nail bed\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Nail plate avulsion and partial normalization of nail apparatus\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Telang (1)\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

Figure 1:a- Onycholysis and onychodystrophy of the right second nail;
b-e surgical resection process ; f -one month after surgery

\textbf{Figure legends}

Figure 1:a- Onycholysis and onychodystrophy of the right second nail;
b-e surgical resection process ; f -one month after surgery

Figure 2: Onycholemmal cyst lining is composed of stratified squamous
epithelium without granular layer supported by a thin fibrous connective
tissue (\selectlanguage{ngerman}×40, H\&E staining)\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

Figure 2: Onycholemmal cyst lining is composed of stratified squamous
epithelium without granular layer supported by a thin fibrous connective
tissue (\selectlanguage{ngerman}×40, H\&E staining)

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