Pigmented basal cell carcinoma of the nipple-areola complex mimicking malignant melanoma in a 61-year-old Thai woman: a case report and literature review

Introduction

Basal cell carcinoma (BCC) is the most common skin cancer, usually arising in sun-exposed areas such as the head and neck (1). Involvement of the nipple-areola complex (NAC) is exceedingly rare, even though cases can occur without well-established risk factors like chronic sun exposure or prior radiation (2). Pigmented lesions of the NAC are particularly challenging because they may mimic both malignant and benign condition, including pigmented Paget’s disease, malignant melanoma, pigmented type of Bowen’s disease (squamous cell carcinoma in situ), seborrheic keratosis, or melanocytic nevus, distinguishing these entities based solely on physical examination is challenging (3-5). Such misdiagnosis may lead to delayed or inappropriate management.

In Asian populations, BCC is generally less prevalent, and reported cases of NAC involvement remain scarce (2). This limited evidence constrains understanding of the clinical presentation and optimal management of pigmented NAC lesions, underscoring the need for additional case documentation.

Current clinical guidelines for BCC management, including those from the National Comprehensive Cancer Network (NCCN) and recent European consensus-based guideline, primarily address risk stratification and treatment selection, including recommended excision margins based on tumor and anatomic risk (6,7). However, these guidelines do not specifically address the diagnostic approach or management considerations for pigmented BCC arising in the NAC, where melanoma and breast-related differentials are frequently prioritized in routine practice. As a result, clinicians may encounter uncertainty in routine clinical pathways when evaluating persistent pigmented NAC lesions and determining the appropriate use and timing of tissue diagnosis.

Herein, we present a rare case of superficial pigmented BCC of the NAC in a 61-year-old Thai woman, emphasizing the diagnostic challenge of melanoma mimicry in this anatomic location. This case underscores the importance of considering pigmented BCC in the differential diagnosis of persistent or atypical pigmented NAC lesions, even in sun-protected areas. We present this article in accordance with the CARE reporting checklist (available at https://gs.amegroups.com/article/view/10.21037/gs-2025-aw-491/rc).

Case presentation

A 61-year-old Thai woman presented with a 1-year history of a non-healing, asymptomatic hyperpigmented lesion over the left NAC. The lesion had been gradually enlarging without associated pain, discharge, or pruritus. The patient did not report obvious evolution in color or surface change, although the lesion had slowly increased in size. She denied any history of trauma, radiation, or prolonged sun exposure to the area. There was no family history of breast or skin malignancy. On physical examination, an irregularly shaped, darkly pigmented macular lesion measuring approximately 1 cm in diameter was observed adjacent to the left nipple (Figure 1). The lesion demonstrated asymmetry, irregular borders, heterogeneous pigmentation, and its diameter exceeded 6 mm, raising clinical suspicion for malignant melanoma based on the ABCDE criteria (Asymmetry, Border irregularity, Color variation, Diameter >6 mm); no definite evolution was reported. No palpable breast mass or axillary lymphadenopathy was noted. The overlying skin was intact, with no signs of ulceration or inflammation. Mammography and breast ultrasonography revealed focal skin thickening at the lesion site, and there was no evidence of an underlying mass or axillary lymphadenopathy (Figure 1). Dermoscopic evaluation was not available in our clinical setting and therefore was not performed, which represents a limitation of the initial clinical assessment. The differential diagnosis included malignant melanoma, pigmented Paget’s disease. A punch biopsy was performed. Histopathologic examination demonstrated basaloid cell proliferation with peripheral palisading within the superficial dermis with intratumoral pigmentation, consistent with low-risk superficial pigmented BCC. Further staging workup showed no evidence of distant metastasis.

Figure 1 Clinical and radiographic findings of the left nipple-areola complex lesion. (A) Clinical photograph showing an irregularly shaped, darkly pigmented macule lateral to the left nipple (arrow) without ulceration or surrounding skin changes. (B) Breast ultrasonography and (C,D) mammography images demonstrating focal skin thickening lateral to the left nipple (asterisk) and no evidence of an underlying breast mass or axillary lymphadenopathy. L MLO, left mediolateral oblique view; R MLO, right mediolateral oblique view.

Definitive surgical excision of the lesion involving the left NAC was subsequently performed without sentinel lymph node biopsy. Excision was planned with approximately 4-mm clinical margins. Final pathology confirmed superficial BCC with negative margins on all sides; the closest histologic margin measured 7 mm, and no lymphovascular invasion was identified (Figure 2). The tumor measured 1.1 cm in greatest dimension, with an invasion depth of 0.2 cm. Postoperative wound healing was uneventful, with no evidence of infection or delayed healing. Sensation over the surrounding periareolar skin was preserved. From a cosmetic perspective, the overall breast contour was satisfactory, with no noticeable deformity. At 6-month follow-up, the patient remained free of recurrence under regular dermatologic and surgical surveillance. The clinical course is summarized in Table 1.

Figure 2 Histopathological features of the excised left nipple-areola complex lesion (hematoxylin and eosin stain). (A) At 40× magnification, multiple nests and cords of basaloid cells (arrows) extend into the superficial dermis without adnexal invasion. (B) At 100× magnification, basaloid cells show peripheral palisading with focal retraction clefts (asterisk) between tumor nests and fibromyxoid stroma, with focal intratumoral pigmentation (arrowhead). (C) At 200× magnification, hyperchromatic nuclei with scant cytoplasm and occasional mitoses are seen. (D) At 400× magnification, melanophages (circle) are evident in the dermis.

All procedures performed in this study were in accordance with the Declaration of Helsinki and its subsequent amendments. This study was approved by the Ethics Committee of Chulabhorn Royal Academy (No. IRB 038/2568). Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

BCC typically arises in sun-exposed areas, such as the head, neck, and upper trunk (1). In contrast, BCC of the NAC is exceedingly rare (2). This anatomic rarity creates a clinically relevant diagnostic problem: persistent NAC lesions are often evaluated first in the context of breast-related diseases (e.g., Paget’s disease or invasive carcinoma involving the nipple) or melanoma when pigmentation is prominent, while cutaneous malignancies such as pigmented BCC may not be readily considered. This case highlights the diagnostic overlap encountered in persistent pigmented NAC lesions; despite initial clinical concern for melanoma based on the lesion’s appearance, histopathology ultimately demonstrated a low-risk superficial pigmented BCC (8).

Although chronic ultraviolet (UV) exposure and prior radiation are established risk factors for BCC, this case illustrates that BCC may also develop in sun-protected areas (1,2). This suggests a role for UV-independent factors, such as spontaneous mutation, immune dysregulation, or local microenvironmental factors (1). These factors may be especially relevant in Asian populations, where overall BCC incidence is lower than in White populations, likely due to darker skin phototypes and reduced cumulative UV exposure.

Although BCC guidelines (e.g., NCCN, European consensus-based guidelines) provide clear recommendations for risk stratification and treatment, they offer limited guidance on the diagnostic approach to uncommon pigmented lesions of the NAC (6,7). Therefore, a systematic diagnostic pathway is particularly important in this setting.

A practical diagnostic approach to pigmented NAC lesions should therefore be systematic. Clinical assessment should document melanoma-associated features (e.g., ABCDE criteria) and evaluate for signs suggestive of Paget’s disease or underlying breast malignancy (e.g., eczematous change, nipple erosion, discharge, subareolar mass) (4,5). Imaging (mammography and ultrasonography) can be useful to exclude an underlying breast mass or nodal involvement when breast-related differentials are considered. Dermoscopy, when available, is a valuable non-invasive adjunct to help distinguish pigmented BCC from melanoma and may demonstrate features suggestive of pigmented BCC (e.g., blue-gray globules, spoke-wheel areas, or other pigmented structures) (4,9). In our case, dermoscopic evaluation was not available in our clinical setting and therefore was not performed, which we acknowledge as a limitation of the initial assessment. Importantly, regardless of dermoscopic availability, histopathological confirmation remains essential for definitive diagnosis when a lesion is persistent, atypical, progressive, or clinically suspicious. In this context, a lower threshold for biopsy may be reasonable for persistent pigmented NAC lesions that do not respond to conservative treatment or that demonstrate subtle progression, even in populations where BCC is less prevalent and NAC involvement is unexpected. Histologically, our case was a superficial BCC, which is generally considered a low-risk subtype (8). Prominent pigmentation can occur in BCC and may lead to clinical overlap with melanoma, especially in pigmented lesions of uncommon sites such as the NAC. Therefore, histopathological confirmation remains essential, and immunohistochemistry may be helpful in diagnostically challenging heavily pigmented cases (10). With respect to management, superficial BCC is generally considered low risk, and complete surgical excision with histologically negative margins remains the mainstay of treatment (6,7). In anatomically sensitive sites such as the NAC, surgical planning should balance oncologic clearance with wound closure and cosmetic considerations. In our patient, excision was planned with approximately 4-mm clinical margins, and final pathology confirmed negative margins on all sides (closest histologic margin 7 mm) without lymphovascular invasion. Sentinel lymph node biopsy is not routinely indicated for clinically node-negative superficial BCC without high-risk features, and adjuvant radiotherapy is typically reserved for select high-risk scenarios (6,7). The postoperative course in this case was uneventful, with satisfactory early cosmetic outcome and no evidence of recurrence at 6-month follow-up. Nonetheless, the follow-up duration is short, and longer surveillance is required because BCC recurrence may occur years after treatment.

Reports of BCC involving the NAC in Asian populations are scarce (2). Our literature review identified 9 reported cases of pigmented BCC of the NAC across Asia (Table 2) (11-19). Collectively, these cases highlight recurring clinical challenges, including melanoma-like presentations that complicated initial recognition, and most were managed surgically with negative margins. However, interpretation of outcomes is limited by small numbers and variable follow-up durations; larger case series or multicenter registries are needed to clarify optimal diagnostic pathways and long-term outcomes for this rare entity.

Conclusions

BCC of the NAC is a rare, and pigmented presentations may clinically mimic malignant melanoma, seborrheic keratosis, pigmented Paget’s disease, and other NAC lesions. Clinicians should maintain diagnostic vigilance for persistent pigmented NAC lesions, incorporate non-invasive assessment such as dermoscopy when available, and pursue timely biopsy when indicated to establish a definitive diagnosis and guide appropriate surgical management. Given the limited follow-up in this report, longer surveillance is required to assess long-term disease control.

Acknowledgments

We gratefully acknowledge Dr. Kristen Sadler from Scribendi (www.scribendi.com) for providing English language editing of the manuscript.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://gs.amegroups.com/article/view/10.21037/gs-2025-aw-491/rc

Peer Review File: Available at https://gs.amegroups.com/article/view/10.21037/gs-2025-aw-491/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://gs.amegroups.com/article/view/10.21037/gs-2025-aw-491/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the Declaration of Helsinki and its subsequent amendments. This study was approved by the Ethics Committee of Chulabhorn Royal Academy (No. IRB 038/2568). Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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