Seborrheic Keratosis Mimicking Basal Cell Carcinoma Under Dermoscopy: A Case Report
Seborrheic keratosis (SK) is one of the most common benign skin tumors encountered in clinical practice. Despite its benign nature, the wide variation in its clinical features can make it challenging to differentiate SK from other benign or malignant skin tumors, particularly when both its clinical manifestations and dermoscopic findings are atypical. This case report highlights a unique instance where an adenoid type of SK mimicked pigmented basal cell carcinoma (BCC) under dermoscopy, emphasizing the complexities involved in accurate diagnosis.
The patient in question was a 49-year-old female who presented with a two-year history of a single, slowly growing papule on her right arm. The lesion was occasionally itchy, and physical examination revealed a 4 mm by 5 mm rough, slightly hard, oval brown papule with central erosion. The clinical appearance of the lesion raised suspicions of a malignant skin tumor, prompting further investigation through dermoscopy.
Dermoscopic examination using a CBS-908 device revealed several features that were initially suggestive of pigmented BCC. The lesion displayed an ulcer and hairpin vessels in the center, surrounded by blue-gray globules and leaf-like areas at the edge. These findings, particularly the presence of pigmented structures without a pigment network, were consistent with a diagnosis of pigmented BCC. However, histopathological examination provided a different perspective.
Histopathologically, the lesion showed acanthosis and thin proliferating strands of basaloid cells arising from the epidermis and twisting in the dermis. The stratum corneum was absent in the middle of the lesion, while pseudohorn cysts were present in the epidermis. The epithelium exhibited hyperpigmentation, with some pigment deposition and inflammatory cell infiltration in the superficial dermis. These histopathological features led to a final diagnosis of an adenoid type of SK, rather than pigmented BCC.
The dermoscopic features of adenoid SK have not been extensively reported in the literature. In this case, the typical dermoscopic findings of SK, such as comedo-like openings, cerebriform pattern, and milia-like cysts, were not clearly visible. Additionally, the lesion did not exhibit typical dermoscopic features of other epidermal hyperplastic tumors, such as Bowen’s disease or keratoacanthoma. The patient’s history of occasional itching suggested that the central erosion surface might have been caused by recent irregular scratching, which could have rendered the dermoscopic findings atypical.
Several dermoscopic details are noteworthy in this case. First, erosion was observed instead of ulceration, although distinguishing between these two processes under dermoscopy can be challenging. Second, hairpin vessels without a white halo were apparent, which are more indicative of SK than the arborizing vessels typical of pigmented BCC. Lastly, the hyperkeratosis on the edge of the lesion and epidermal hyperpigmentation, along with free pigment and melanophages in the dermal papilla, were initially mistaken for leaf-like areas and blue-gray globules characteristic of pigmented BCC nests.
This case underscores the importance of not relying solely on dermoscopy for diagnosis, particularly when dealing with atypical presentations. The adenoid type of SK, especially when subjected to scratching or trauma, can mimic pigmented BCC under dermoscopy, making accurate diagnosis more challenging. In such cases, a comprehensive approach that includes auxiliary examinations, detailed medical history, and clinical characteristics is essential for making a differential diagnosis.
In conclusion, while dermoscopy is a valuable tool in the diagnosis of SK, it is not infallible. The adenoid type of SK can present with dermoscopic features that closely resemble those of pigmented BCC, particularly when secondary injuries such as scratching are involved. Therefore, clinicians should be cautious and employ a multifaceted diagnostic approach to ensure accurate diagnosis and appropriate management.
doi.org/10.1097/CM9.0000000000001010
Was this helpful?
0 / 0