Dermatology: Practical and Conceptual


Letter  |  Dermatol Pract Concept 2020;10(1):e2020013 1

Dermatology Practical & Conceptual

Introduction 

Keratoacanthoma is a relatively common, low-grade cuta-

neous tumor that most commonly exhibits a self-limiting 

behavior. The lesions present as firm, sharply defined nodules 

with a central ulceration or prominent keratin plug. Pertinent 

physical findings are usually limited to the skin, with the 

majority of the lesions favoring the sun-exposed areas [1].

Histopathological characteristics highly resemble those 

of squamous cell carcinoma. Observation strategy is ques-

tionable and rarely practiced as a therapeutic means. Surgical 

excision of the entire lesion is a gold standard regimen [1,2].

Case Presentation

A 65-year-old Caucasian man with an unremarkable med-

ical history presented with a 1-month history of 2 painless 

nodules in a linear arrangement on his right leg (Figure 1, 

A and B). The patient reported that both lesions appeared 

1 week after he sustained a penetrating plant thorn injury 

while fishing in fresh water. Prior to clinical admission he 

had received amoxicillin/clavulanic acid by mouth along with 

topical fusidic acid cream for 2 weeks without noticeable 

clinical improvement.

Cutaneous examination revealed 2 dome-shaped, well-de-

marcated, flesh-colored, nontender nodules with peripheral 

scaling and central crust, arranged in a sporotrichoid fashion 

over the pretibial area of the right leg. The proximal and the 

distal lesions were located inferior to the patient’s knee and 

on the lower part of his right shin, respectively. Enlarged 

lymph nodes were palpated in the right inguinal area. He was 

afebrile and the overall physical examination was normal. 

Differential diagnosis included keratoacanthomas, cutaneous 

sporotrichosis, nocardiosis, Mycobacterium marinum infec-

tion, and Merkel cell carcinomas.

Routine hematological, biochemical, and immunological 

investigations were either negative or within normal range. 

Mantoux test was negative and chest x-ray revealed no 

pathological findings.

Direct Gram stain, periodic acid-Schiff stain, Ziehl- 

Neelsen and Giemsa stains as well as tissue cultures were 

found negative for mycobacteria, protozoa, fungi, and yeasts, 

including Nocardia brasiliensis, Sporothrix schenckii, Myco-

bacterium marinum, Actinomyces, and Leishmania, and 

positive for Serratia marcescens and Escherichia coli, which 

were considered bacterial contamination.

Two 6-mm punch biopsies were obtained for histopatho-

logical examination. Polymerase chain reaction for detection of 

Cutaneous Nodules Arranged in a Sporotrichoid 
Distribution Over the Lower Extremity

Georgia Kyriakou,1 Eleftheria Vryzaki,1 Efthymia Gialeli,1 Sophia Georgiou1

1 Department of Dermatology, University General Hospital of Patras, Greece

Key words: keratoacanthoma, skin neoplasms, squamous cell carcinoma

Citation: Kyriakou G, Vryzaki E, Gialeli E, Georgiou S. Cutaneous nodules arranged in a sporotrichoid distribution over the lower 
extremity. Dermatol Pract Concept. 2020;10(1):e2020013. DOI: https://doi.org/10.5826/dpc.1001a13

Accepted: September 16, 2019; Published: December 31, 2019

Copyright: ©2019 Kyriakou et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, 
which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: None.

Competing interests: The authors have no conflicts of interest to disclose.

Authorship: All authors have contributed significantly to this publication.

Corresponding author: Georgia Kyriakou, MD, MsC, cPhD, University General Hospital of Patras, Rion, Patras, P.O. 265 04, Greece. 
Email: geo_kyr@yahoo.gr

mailto:geo_kyr@yahoo.gr


2 Letter  |  Dermatol Pract Concept 2020;10(1):e2020013

mycobacteria was negative. Pending the 

biopsy results and given the clinical sus-

picion of lymphocutaneous sporotricho-

sis, the patient commenced a course of 

systemic antibiotics and antifungals.

Since the biopsy results were consis-

tent only with pseudoepitheliomatous 

hyperplasia, and minimal improve-

ment was noticed during the antibiotic 

and fungal treatment, we proceeded 

to complete surgical excision of both 

lesions. The biopsied tissue specimens 

were additionally stained with periodic 

acid-Schiff and Grocott-Gomori stains 

without identification of an infectious 

agent. Histopathology was consistent 

with keratoacanthomas in regression 

stage (Figures 2 and 3). There was no 

evidence of regional lymphadenopathy 

or relapse at the follow-up visit, con-

ducted 6 months later.

Conclusions

Apart from infectious diseases, a number 

of neoplasms are uncommonly described 

to present in a sporotrichoid fashion. 

These include melanoma, squamous cell 

carcinoma, B-cell and T-cell lymphoma, 

Langerhans cell histiocytosis, peripheral 

nerve sheath tumor, and epithelioid sar-

coma [2]. Nevertheless, in the majority 

of cases the tumors represented recurrent 

or metastatic disease rather than primary 

neoplasms. To our knowledge, a simi-

lar pattern of keratoacanthomas with 

each lesion being a primary tumor was 

first reported by Abudu and Cohen [2]. 

Our patient is the second case described, 

thus rendering it a necessity to take ker-

atoacanthomas into consideration when 

encountering atypical cutaneous lesions 

arranged in a sporotrichoid pattern.

References

1. Kwiek B, Schwartz RA. Keratoacanthoma 

(KA): an update and review. J Am Acad 

Dermatol. 2016;74(6):1220-1233.

2. Abudu B, Cohen PR. Sporotrichoid kera-

toacanthomas: case report and review of 

neoplasms presenting in a sporotrichoid 

pattern. Cureus. 2018;10(8):e3196.

Figure 1. (A) Keratoacanthomas in spo-

rotrichoid distribution presenting as firm, 

sharply defined, dome-shaped nodules with 

a purulent, ulcerated surface. The distal le-

sion was 2.0 × 2.0 cm and located on the 

lower part of the patient’s right shin, while 

the proximal lesion was 2.5 × 2.5 cm and 

presented an ill-defined broad halo of  sur-

rounding rubor and edema (B).

A B

Figure 2. Histopathological examination of the biopsy specimen revealing a central crater 

filled with keratin (keratin plug), downward cupping of the epidermis, and hyperkeratosis 

with little or no parakeratosis (H&E, ×40).

Figure 3. Keratin-producing squamous cells demonstrate minimal or absence of nuclear 

atypia. Marked inflammatory cell infiltrate is present around the lesion (H&E, ×200).