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\begin{document}

\title{Diagnostic Features of a Non-Pigmented Eccrine Poroma with a Collarette:
Histopathological and Dermoscopic Correlation}



\author[1]{Tomoaki Takada}%
\affil[1]{Affiliation not available}%


\vspace{-1em}



  
  \date{May 25, 2024}


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\selectlanguage{english}
\begin{abstract}
We report a dermoscopic diagnostic clue for non-pigmented eccrine poroma
found in a collarette, which is thought to be a nonspecific site.%
\end{abstract}%



\sloppy


\textbf{1. INTRODUCTION}

Eccrine poromas (EPs) are rare benign adnexal tumors of various
histological types that are dermoscopically challenging to
diagnose.\textsuperscript{1} We present a non-pigmented EP surrounded by
a collarette showing a whitish-pink ovoid nest and translucent-brown
globules with poorly visualized vessels on dermoscopy. A collarette is a
narrow rim of loosened keratin overhanging the periphery of a
circumscribed skin lesion attached to the normal surrounding
skin.\textsuperscript{2} Because the dermoscopic examination of
structures in the collarette was insufficient, a histopathological
examination was performed. We identified the most common type of tumor
in the dermis in continuity with the epidermis.

\textbf{2. CASE PRESENTATION}

2.1 Case history and examination

A 65-year-old man presented with a 6.5 \selectlanguage{ngerman}× 4.5-mm, symmetrical,
well-circumscribed, non-pigmented, deep-red papule surrounded by an
indented moat with collarette scales, on the right thigh (\textbf{Figure
1} ). The patient had experienced trace bleeding and painful eruption 3
days prior.

Dermoscopic examination revealed milky-red globules and chalice-like
vessels surrounded by a well-circumscribed hyperkeratotic rim showing a
white double-ring configuration due to thick scales. In the collarette,
a whitish-pink ovoid nest and translucent-brown globules with poorly
visualized vessels were observed (\textbf{Figure 2} ). Chalice-like
vessels were classified as branched vessels with rounded, looped, or
coiled terminal endings and characteristic rounded silhouettes.

Histologic examination revealed sharply circumscribed, small cuboidal
epithelial cells with monomorphous ovoid nuclei and compact eosinophilic
cytoplasm. Cytoplasmic vacuoles were observed. The lesion was a poroid
neoplasm mainly on the dermis and continued into the epidermis. The
surrounding stroma was edematous with dilated vessels of various sizes.
The area of the tumor showed parakeratotic hyperkeratosis with crusting,
and the granular layers had thinned or disappeared (\textbf{Figure 3} ).
At the boundary with the normal skin tissue, epithelial invagination was
noted. In the normal skin tissue at the margin of the tumor,
orthokeratotic hyperkeratosis, hypergranulosis, and irregular epidermal
hyperplasia were observed. In the protuberance of the normal skin tissue
at the epithelial invagination and tumor margin, fissures and tearing of
the thickened stratum corneum could be recognized. Invasion and
anastomotic images of the tumor nest were identified outside the
epidermal invagination, and the surrounding stroma was~mildly edematous
with poorly visualized vessels (\textbf{Figure 4, A--D} ). A tumor
tissue specimen was cut vertically, and four collarette parts at both
ends were examined as histopathological images.

2.2 Differential diagnosis, investigation, and treatment

A clinical diagnosis of EP was made, and surgical resection of the
affected tissue with a 2-mm margin of normal tissue was performed.
Written informed consent was obtained from the patient for the use of
the tissue samples in this study.

2.3 Outcome and follow-up

The final diagnosis based on histopathological findings was EP, which
was completely curatively resected. The postoperative course was
encouraging, showing no evidence of a local recurrence. At present, 1
year after the operation, no findings suggesting a recurrence have been
recognized and careful postoperative follow-up is planned.

\textbf{3. DISCUSSION}

Poroma was first reported in 1956\textsuperscript{3} and with epithelial
invagination in 1958.\textsuperscript{4} However, the correlations
between dermoscopic findings of poroma and the pathological findings
remain poorly characterized. In 2018, dermoscopic findings showed white
interlacing areas around vessels, yellow structureless areas, milky-red
globules, poorly visualized vessels, and branched vessels with rounded
endings. The presence of any of these five features was associated with
poroma with a sensitivity and specificity of 62.8\% and 82.0\%,
respectively.\textsuperscript{1} The histopathological examinations
showed symmetrical, sharply circumscribed anastomosing bands of small,
monomorphic cuboidal epithelial cells, with intercellular bridges in
continuity with the epidermis, and no peripheral nuclear palisading. The
dermal papillae appeared swollen and filled with several dilated vessels
with thickened walls, surrounded by a fibrinoid edematous halo combined
with peripheral lamellar fibroplasia. These findings appeared to be more
pronounced on the sole than on the back. The pink-white structureless
areas and the white-to-pink halo were associated with specific
histopathological features, comprising dermal lamellar fibroplasia and
fibrinoid edema surrounding several dilated vessels,
respectively.\textsuperscript{5} The characteristic feature was
described as well-circumscribed reddish globule\selectlanguage{english}/lacuna-like structures
with separation of mesh bands, which were reminiscent of frog-egg
aggregations. This characteristic feature on dermoscopy was explained by
the histopathological features observed in horizontal sections:
island-shaped edematous stroma with numerous microvessels embedded in a
mass of poroid cells of mesh-like form.\textsuperscript{6} Distinct
dermoscopic features appeared to be recurrent in each histopathological
variant. Dermoscopy can provide important clues for the diagnosis of EP,
although the final diagnosis requires histopathological examination.
Because of its clinical and dermoscopic variability, surgical excision
is recommended to achieve a correct diagnosis of EP.\textsuperscript{7}

A collarette in dermatology refers to a narrow rim of loosened keratin
overhanging the periphery of a circumscribed skin lesion and attached to
the normal surrounding skin. The outer margin of the collarette is
adherent, while the inner margin is free. In practice, however, the skin
forming the collarette may be scaly or thick and ridge-like, forming a
rim around the lesion. While many disorders primarily exhibit such a
morphology, it may be a secondary or a nonspecific manifestation in
certain others. Dermatoses exhibiting a scaly collarette have been
reported in skin tumors such as clear-cell acanthoma, pyogenic
granuloma, acral fibrokeratoma, supernumerary digit, cutaneous horn,
subungual exostosis, eccrine poroma, acral fibromyxoma, stucco
keratosis, and juvenile xanthogranuloma.\textsuperscript{2} In
non-pigmented skin disorders, collarette scaling and scales are defined
dermatoscopically as fragments of scales attached at the periphery and
hanging like curtains, and as white homogeneous structures,
respectively.\textsuperscript{8}

The dermoscopic findings and the corresponding pathological findings in
this case can be stratified according to a) collarette parts and b)
non-collarette parts. In collarette parts, the dermoscopic findings
were: 1) whitish-pink ovoid nest, 2) translucent brown dotted with
poorly visualized vessels, and 3) white double-ring translucent
collarette. The pathological findings were: 1) invasion and anastomotic
images from the tumor nest recognized outside the epidermal
invagination, 2) mildly edematous surrounding stroma with absence of
branched vessels with rounded endings, and 3) well-circumscribed
hyperkeratic rim showing a double-ring configuration due to thick
scales. The inner ring-like segment was consistent with the epidermal
invagination. In non-collarette parts, the dermoscopic findings were: 1)
milky-red globules, 2) chalice-like vessels, and 3) fragments of scales.
The pathological findings were: 1) poroid neoplastic lesions mainly on
the dermis and continuing into the epidermis, small ducts and
occasionally cystic spaces within the aggregations of tumor cells, and
the edematous surrounding stroma with dilated vessels of various sizes;
2) polymorphous vascular pattern, including at least two types of
vascular structures showing irregular linear vessels with
semi-elliptical endings giving the appearance of a chalice; and 3)
parakeratotic hyperkeratosis with crusting in the area of the tumor and
thinned or absent granular layers. The characteristic dermoscopic
findings\textsuperscript{1} allowed each of the above two sites, (a) and
(b), to be diagnosed in isolation as poroma.

Thus, the dermoscopic image mainly comprised tumor with vascular
structures located in the interstitial tissue, and the histopathology
image further identified alterations in the spread of the tumor in the
dermis, degree of inflammation, vascular hyperplasia in the interstitial
tissue, and morphology of the lumens. Multiple elements were considered
to combine to form a dermoscopic image. In this study, we reported the
diagnostic clue of dermoscopy of non-pigmented EP in collarette, which
is thought to be a nonspecific site. Because this is a single case
report, an accumulation of further studies is required. In conclusion,
this was a case that recognized the need for detailed observation of the
entire lesion in dermoscopic examination.

\textbf{ACKNOWLEDGMENT}

I am grateful to the patient for providing consent for the use of his
samples in this study. I also thank Wiley Editing Service for English
language editing.

\textbf{CONFLICT OF INTEREST}

None declared.

\textbf{AUTHOR CONTRIBUTIONS}

TT: Collected the data and wrote the manuscript.

\textbf{REFERENCES}

1. Marchetti M. A., Marino M. L., Virmani P., et al. 2018. Dermoscopic
features and patterns of poromas: a multicenter observational
case-control study conducted by the International Dermoscopy Society. J
Eur Acad Dermatol Venereol. 32:1263-1271. doi:10.1111/jdv.14729

2. Adya K. A., Inamadar A. C., Palit A. 2019. Dermatoses with
''collarette of skin.'' Indian J Dermatol Venereol Leprol. 85:116-124.
doi:10.4103/ijdvl.IJDVL\_623\_17

3. Pinkus H., Rogin J. R., Goldman P. 1956. Eccrine poroma; tumors
exhibiting features of the epidermal sweat duct unit. AMA Arch Derma.
74:511-521. doi:10.1001/archderm.1956.01550110055013

4. Knox J. M., Spiller W. F. 1958. Eccrine poroma. AMA Arch Derma.
77:726-729. doi:10.1001/archderm.1958.01560060092020

5. Ferrari A, Buccini P, Silipo V, et al. 2009. Eccrine poroma: a
clinical-dermoscopic study of seven cases. Acta Derm Venereol.
89:160-164. doi:10.2340/00015555-0608

6. Minagawa A., Koga H., Takahashi M., Sano K., Okuyama R. 2010.
Dermoscopic features of nonpigmented eccrine poromas in association with
their histopathological features. Br J Dermatol. 163:1264-1268.
doi:10.1111/j.1365-2133.2010.10017.x

7. Chessa M. A., Patrizi A., Baraldi C., Fanti P. A., Barisani A.,
Vaccari S. 2019. Dermoscopic-histopathological correlation of eccrine
poroma: an observational study. Dermatol Pract Concept. 9:283-291.
doi:10.5826/dpc.0904a07

8. Zalaudek I., Argenziano G., Stefani A., et al. 2006. Dermoscopy in
general dermatology. Dermatology. 212:7-18. doi:10.1159/000089015

\textbf{FIGURE LEGENDS}

\textbf{FIGURE 1.} Clinical image of the eccrine poroma with collarette.

\textbf{FIGURE 2.} Dermoscopic image of the eccrine poroma with
collarette. Milky-red globules and chalice-like vessels are observed.
The whitish-pink, ovoid nest and translucent-brown globules with poorly
visualized vessels in the collarette are shown (arrows).

\textbf{FIGURE 3.} Histopathological image of the eccrine poroma with
collarette, low- and high-power views. The red box indicates the
collarette area. The inner and outer borders of the collarette
correspond to the depressed part of the epidermal invagination and the
prominent part of the tumor, respectively. Small, cuboidal epithelial
cells with monomorphous ovoid nuclei forming a broad, mesh-like
structure, as well as cytoplasmic vacuoles (arrow) are shown.
Hematoxylin-eosin stain. Original magnification, x20; scale bar, 1 mm.
Inset (black box): x400; scale bar, 50 \selectlanguage{greek}μ\selectlanguage{english}m.

Figure 4. Histopathological images of four collarette parts (A--D). The
invasion and anastomotic images of the tumor nest are recognized outside
the epidermal invagination, and the surrounding stroma is mildly
edematous with poorly visualized vessels (black arrowheads).
Hematoxylin-eosin stain. Original magnification, \selectlanguage{ngerman}×50; scale bar, 500 \selectlanguage{greek}μ\selectlanguage{english}m.\selectlanguage{english}
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