A 54-year-old man presented with a solitary keratotic nodule on his right hand that had been present for 10 years. The lesion was excised and microscopic examination found hyperkeratosis, epithelial hyperplasia, and extensive suprabasilar and intraspinous acantholysis. This finding was consistent with acantholytic acanthoma, a benign tumor characterized by acantholysis. Acantholytic acanthoma is usually asymptomatic, presents as a solitary hyperkeratotic papule, and is diagnosed through histological examination correlating clinical and pathological features to differentiate it from other acantholytic disorders. Simple excision is the treatment for this benign condition.

1. TheJournal of Dermatology
Vol. 27: 127-128,2000
Acantholytic Acanthoma
To the Editor: A 54-year-old Korean man
presented with a solitary keratotic nodule
on his right hand for about ten years. On ex-
amination, a solitary, 1.5 x 1.0 em, erythe-
matous, centrally crusted keratotic nodule
was seen on the dorsum of his right hand
(Fig. 1). He had a history of surgical re-
moval of squamous cell carcinoma on his
cheek three months earlier. Other medical
and family history and a review of systems
were unremarkable. The lesion was totally
excised and submitted to histopathological
examination. On microscopic examination,
the nodule revealed hyperkertosis and ep-
ithelial hyperplasia with extensive suprabasi-
lar and intraspinous acantholysis. Within
the dermis, superficial dermal lymphohisti-
.ocytic infiltrates were seen (Fig. 2). There
was no inflammatory exocytosis or cytologic
atypia in basal keratinocytes.
Benign acanthomas, benign tumors of
epidermal keratinocytes, show a variety of
histologic patterns, including epidermoid
keratinization (seborrheic keratosis), granu-
Letter:s to the Editor
Fig. 1. Solitary, centrally crusted, keratotic
nodule on the dorsum of the right hand
lar degeneration (epidermolytic acan-
thoma), cornoid lamellation (porokerato-
sis), and absence of keratinization (clear
cell acanthoma) (1). Acantholytic acan-
thoma is a benign cutaneous tumor first de-
scribed by Brownstein in 1985 (2). In 1988,
he described 31 benign acanthomas in
which acantholysis was the hallmark and
termed them acantholytic acanthoma (1).
Fig. 2. Hyperkeratosis
and epithelial hyper-
plasia with prominent
acantholysis in the
suprabasal and intra-
spinous layer (Hema-
toxylin-eosin, xlOO).
Inset; Higher magnifi-
cation (Hematoxylin-
eosin, x200)

2. 128
The most common clinical presentation was
a solitary, usually hyperkeratotic papule with
occasional crusting. Barnette and Cobb pre-
sented a molluscum contagiosum-like lesion
due to central umbilication (3). Most of
these cases was asymptomatic; pruritus was
sometimes present. There was a truncal
predilection, and the palms, soles, face, and
mucous membranes were usually spared.
Most patients were over 50 years of age, and
men were more commonly affected (ratio,
2:1). The most frequent clinical diagnosis
was seborrheic keratosis or actinic keratosis;
rarely, it was basal cell carcinoma. The cause
of acantholytic acanthoma as well as its rela-
tionship to other diseases is unknown, but
Ramos-Caro et al. reported a case in an im-
munosuppressed patient and suggested the
role of decreased immune surveillance in
the production of this lesion (4). Our pa-
tient was otherwise healthy except for the
history of squamous cell carcinoma on his
left cheek, of which there was no evidence
of recurrence after surgical removal. Histo-
logical differential diagnosis included pem-
phigus group, Grover's disease, and Hailey-
Hailey disease. However, our patient had no
evidence of these diseases, so it is important
to correlate the pathologic features with
clinical ones. Acantholytic seborrheic ker-
atosis shows the general configuration of se-
borrheic keratosis with only small foci of
acantholysis (5). If prominent dyskeratosis
is seen, warty dyskeratoma or papular acan-
tholytic dyskeratolysis of genitalia must be
considered (6). In acantholytic solar kerato-
sis, the acantholysis occurs just above the
atypical cells of the basal layer. When the
atypia is full-thickness or high grade, the
term acantholytic squamous cell carcinoma
in situ can be used (7).
We describe a case of acantholytic acan-
thoma on the dorsum of the hand. Because
Kim et al
acantholytic acanthoma is a benign disor-
der, simple excision is the treatment of
choice. Knowledge of this entity can help to
differentiate numerous acantholytic disor-
ders and to avoid unnecessarily extensive
treatment.
So-Hyung Kim
Jee-Ho Choi
Kyung:Jeh Sung
Kee-Chan Moon
Jai-Kyoung Koh
Department of Dermatology
Asan Medical Center, College of Medicine
University ofUlsan, Seoul, Korea
Reprint requests to: Jee-Ho Choi, M.D.
Department of Dermatology
Asan Medical Center, College of Medicine
University of Ulsan, 388-1
Poongnap-Dong, Songpa-Gu, Seoul
138-736, Korea
References
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