Dermatology: Practical and Conceptual


Image Letter | Dermatol Pract Concept. 2024;14(3):e2024195 1

Perianal Basal Cell Carcinoma:  
A Diagnostic Challenge

Silvia Giordano1, Francesc Alamon-Reig2, Mar Luque Luna2, Paola Castillo3,  
Agustí Toll4, Cristina Carrera2,5

1 Dermatology Clinic, Department of Medical Science, University of Turin, Turin, Italy

2 Department of Dermatology, University of Barcelona, Hospital Clinic of Barcelona, Barcelona, Spain

3 Departments of Pathology, Hospital Clinic of Barcelona, Barcelona, Spain

4 Department of Dermatology, Hospital del Mar, Universitat Autònoma de Barcelona (UAB), Barcelona, Spain

5 Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto Carlos III, Barcelona, Spain

Citation: Giordano S, Alamon-Reig F, Luna ML, Castillo P, Toll A, Carrera C. Perianal Basal Cell Carcinoma: A Diagnostic Challenge. 
Dermatol Pract Concept. 2024;14(3):e2024195. DOI: https://doi.org/10.5826/dpc.1403a195

Accepted: March 3, 2024; Published: July 2024

Copyright: © Giordano et al. This is an open-access article distributed under the terms of the Creative Commons Attribution-
NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, 
distribution, and reproduction in any medium, provided the original authors and source are credited.

Funding: None.

Competing Interests: None.

Authorship: All authors have contributed significantly to this publication.

Corresponding Author: Silvia Giordano, Dermatology Clinic, Department of Medical Science, University of Turin, Turin, Italy.  
Email: si.giordano@unito.it

Case Presentation

A 70-year-old woman with a history of uterine prolapse 

presented with an asymptomatic ulcerated dark plaque 

with mucocutaneous involvement in the anorectal region 

(Figure 1A). Dermoscopically, the lesion exhibited globular 

blue-black areas with atypical vessels, blue-grey dots, and 

white structureless areas (Figure 1B). Melanoma was first 

suspected; however, the biopsy revealed an infiltrating pig-

mented basal cell carcinoma (BCC) (Figure 1C). The MRI 

examination revealed a mucosal involvement with extension 

up to the internal sphincter (Figure 1D). At the multidisci-

plinary tumor board, oral hedgehog inhibitor therapy with 

vismodegib was initiated, with remarkable shrinkage after 

three months and good tolerance, thus avoiding mutilating 

surgery.

Teaching Point

BCCs in non-sun-exposed areas are exceedingly rare, the 

anorectal region being the rarest site, comprising less than 

0.2% of all BCC cases. This rarity, combined with its ten-

dency to present atypically, often makes diagnosis challeng-

ing as it can mimic benign conditions but also malignant 

tumors like pigmented squamous cell carcinoma or mela-

noma, as they are more frequent than BCC in this location.



2 Image Letter | Dermatol Pract Concept. 2024;14(3):e2024195

References

1. Tsai TY, Liao CK, Zhang BY et al. Perianal Basal Cell  Carcinoma- 

A Systematic Review and Meta-Analysis of Real-World Data. 

Diagnostics (Basel). 2023 May 8;13(9):1650. doi: 10.3390/ 

diagnostics13091650. PMID: 37175041; PMCID: PMC10178443.

2. Gibson GE, Ahmed I. Perianal and genital basal cell carcinoma: 

A clinicopathologic review of 51 cases. J Am Acad Dermatol. 

2001 Jul;45(1):68-71. doi: 10.1067/mjd.2001.114588. PMID: 

11423837.

Figure 1. (A) Clinical and (B) dermoscopic images of the perianal lesion. (C) Infiltrated basal cell carcinoma. (D) MRI shows mucosal 

involvement up to the internal sphincter.