Dermoscopy and reflectance confocal microscopy‐augmented characterization of pigmented micro‐basal cell carcinoma (less than 2 mm diameter)

Abstract

Background

Basal cell carcinoma (BCC) is the most common skin cancer, accounting for approximately 80% of nonmelanoma skin cancer diagnoses each year. Among other factors, the staging of BCC is influenced by its measured diameter. Stage 1 BCC is defined as a lesion measuring 2 cm across or less. Of note, there have been increasing publications reporting features of “small‐sized” BCCs, which can present smaller than 1 mm. However, few of these studies have characterized features of pigmented small‐sized BCC. The application of in‐vivo imaging such as dermoscopy and reflectance confocal microscopy (RCM) allows for the non‐invasive distinction of these lesions from benign and malignant melanocytic neoplasms, thereby reducing unnecessary biopsies.

Methods

Within one year, three patients presented to Oregon Health and Science University's dermatology clinic with pigmented lesions of concern measuring less than 2 mm that were histologically confirmed as pigmented BCC. We sought to characterize the features of these lesions in a case series with the non‐invasive imaging modalities of dermoscopy and RCM.

Results

All cases presented clinically as a small, brown, macule on the face. Each of the three cases exhibited differing features on dermoscopy. With the application of RCM, we were able to visualize characteristic BCC features, prompting removal by shave biopsy.

Conclusion

To our knowledge, no other study has reported dermoscopic and RCM features of a cohort of pigmented BCCs 2 mm in diameter or smaller. We propose to define BCCs of this size as micro‐BCCs. The variability of dermoscopic findings observed in our study, combined with the small size of these pigmented lesions, shows the utility of RCM as a non‐invasive diagnostic tool for pigmented micro‐BCCs.

1. INTRODUCTION

Basal cell carcinoma (BCC) is the most common malignancy in the United States, with a minimum of 2 million new cases being diagnosed yearly, and an incidence that continues to rise. ¹ , ² , ³ Early detection of BCC is imperative to decrease morbidity from this disease. ¹ , ² , ³ , ⁴ The literature has demonstrated that dermoscopy‐augmented examination of the skin improves both the sensitivity and specificity of BCC detection, particularly in distinguishing pigmented BCCs from melanoma. ¹ , ² , ³ , ⁴ , ⁵ Dermoscopic features of BCC have been widely characterized, although the combination of those present varies between lesions. Commonly reported structures can include arborizing telangiectasias, blue‐grey ovoid nests, and shiny white structures, among others. ⁵ , ⁶ , ⁷ , ⁸ , ⁹ , ¹⁰ Though dermoscopy is a valuable tool for the detection of BCCs, its utility in clinical practice is highly user‐dependent, thus strengthening the need for documentation of dermoscopic findings in unique presentations of skin disease. Moreover, the application of additional imaging modalities, such as reflectance confocal microscopy (RCM), further characterizes these diseases to aid in their early detection. ¹¹ , ¹² , ¹³

Previous publications have illustrated clinical features of small‐sized BCCs, typically 5 mm in diameter or smaller. There is a paucity of literature demonstrating dermoscopic and RCM features of BCCs measuring 2 mm or less, (which we refer to as micro‐BCCs) that are also pigmented. Because pigmented lesions this small of size are difficult to distinguish from malignant melanoma, describing the dermoscopic and RCM features of our cases will add to the literature and support diagnosticians in identifying these unique lesions with confidence. Herein we present three cases of pathologically‐confirmed, pigmented micro‐BCCs seen at the Oregon Health and Science University Department of Dermatology between 2021 and 2022, each with a diameter measured by digital dermoscopy (Heine Delta 30; Heine USA, Dover, NH), of 2 mm or smaller. Each of these cases has distinct features visualized on dermoscopy and RCM (Vivascope 3000; Caliber I.D., Rochester, NY) discussed in this paper. Our intention is not to suggest overtreatment, but rather to exhibit that the application of the newest technology enables early detection of this rare presentation of a common disease.

1.1. Case 1

A 48‐year‐old Fitzpatrick skin type II male with no history of skin cancer presented to the dermatology clinic for a full body skin examination without any reported concerns. Physical examination revealed a 0.9 mm light brown, asymmetric papule on the left forehead (Figure 1A). The lesion was further evaluated with a dermatoscope and digital images were taken, illustrating what appeared as blue‐grey dots and blue‐grey ovoid nests. (Figure 1B). These features in conjunction with the absence of pigmented network on dermoscopy suggested a possible diagnosis of pigmented BCC rather than a melanocytic neoplasm, though the small size of the lesion left remaining uncertainty and prompted more extensive visualization with RCM. RCM was therefore performed to obtain cellular and sub‐cellular imaging of the lesion. The epidermal architecture was irregular and exhibited enlarged keratinocytes in a predominantly honeycombed pattern. Inflammatory cells (melanophages) were present. Tumor islands, palisading of nuclei, and clefting were present, determining the diagnosis of BCC (Figure 1C). The patient was informed of the nature of the findings and a biopsy by shave removal technique was performed. Dermatopathology reported microscopic findings of nodular aggregates of cells within the dermis, with many of the cells containing hyperchromatic nuclei, scant cytoplasm, and palisading of the peripheral nuclei; confirming nodular basal cell carcinoma (Figure 1D). The patient was recommended for removal of the lesion by Mohs micrographic surgery.

FIGURE 1.

Clinical, dermoscopic, reflectance confocal microscopy (RCM), and histologic characteristics of a 0.9 mm pigmented basal cell carcinoma. Panel A shows the left forehead location (annotated by a black arrow). Panel B indicates the dermoscopic presence of blue‐grey dots and blue‐grey ovoid nests as well as an absence of a pigment network. Panel C showcases RCM features of tumor islands (indicated by red stars) encompassed by palisading nuclei (yellow arrow) and clefting (red arrow). Panel D presents the lesion's pathology slide (8X), with tumor islands in the dermis containing aggregates of basaloid cells (red stars), peripheral palisading nuclei (yellow arrow), and the presence of clefting

1.2. Case 2

A 73‐year‐old Fitzpatrick skin type II male with a history of multiple melanomas presented for a full‐body skin examination. He was seen 6 months prior for Mohs surgery to remove two BCCs. On physical examination, a 2 mm pigmented lesion on the left upper forehead was identified (Figure 2A). Due to the patient's extensive history of melanoma, the lesion was further investigated to rule out melanoma recurrence. The addition of dermoscopy to characterize the lesion expanded the differential to include nonmelanoma skin cancer. Spoke‐wheel structures and blue‐grey dots were present; features that are suggestive of BCC (Figure 2B). RCM permitted more extensive visualization of the epidermis with irregular and enlarged keratinocytes, predominantly in a honeycombed pattern. Melanophages were present. Tumor islands, palisading of nuclei, and clefting were present (Figure 2C). Each of these features was consistent with a diagnosis of BCC, rather than melanoma as initially suspected. Therefore, a biopsy by shave technique was performed, with histologic findings of basaloid epithelial cell aggregates, hyperchromatic nuclei, scant cytoplasm, and palisading of the peripheral nuclei (Figure 2D). This further supported the diagnosis of pigmented BCC. The patient was subsequently referred to Mohs micrographic surgery for removal.

FIGURE 2.

Clinical, dermoscopic, reflectance confocal microscopy (RCM), and histologic characteristics of a 2 mm pigmented basal cell carcinoma. Panel A shows the location on the left upper forehead (black arrow). Panel B indicates dermoscopic features of the same lesion, with the presence of spoke wheel structures and blue‐grey dots. Panel C demonstrates a tumor island (red star) with palisading nuclei (yellow arrow) and clefting (red arrow), visualized with RCM. Panel D is the lesion's dermatopathology slide (8x), containing basaloid nests of hyperchromatic nuclei (red star) with peripheral palisading nuclei (yellow arrow) and visible clefting

1.3. Case 3

A 44‐year‐old Fitzpatrick skin type I female with a history of melanoma in‐situ presented for a spot check of a 1.5 mm pigmented macule on the left upper lip (Figure 3A). She noted that the lesion had been present for several years yet had recently changed in shape and size. She was concerned for melanoma in consideration of the dark pigment in the lesion. The lesion was visualized with dermoscopy in clinic, and the distribution of pigment on dermoscopy yielded two differential diagnoses. The first dermoscopic interpretation of the small lesion was lentigo maligna due to pigment distribution suggestive of perifollicular hyperpigmentation, whereas the secondary diagnostic consideration was pigmented BCC with consideration of possible maple leaf‐like structures (Figure 3B). RCM imaging revealed an irregular epidermal architecture with enlarged keratinocytes, predominantly in a honeycombed pattern, with melanophages, tumor islands, and palisading of nuclei; confirming the diagnosis of BCC and ruling out lentigo maligna (Figure 3C). The skin tumor was completely removed by punch biopsy with visible clear margins. Histology showed irregular aggregates of basaloid epithelial cells, hyperchromatic nuclei, scant cytoplasm, peripheral nuclear palisading and areas of pigment (Figure 3D). This ultimately confirmed a pathologic diagnosis of BCC. The patient declined Mohs micrographic surgery and elected to treat the lesion topically with 5‐fluorouracil cream and close monitoring with their dermatologist.

FIGURE 3.

Clinical, dermoscopic, reflectance confocal microscopy (RCM), and histologic characteristics of a 1.5 mm pigmented basal cell carcinoma. Panel A shows the location on the left upper lip (black arrow). Panel B reveals dermoscopic visualization of the lesion, with brown pigment distribution suggestive of maple leaf‐like structures, or possible consideration of perifollicular hyperpigmentation. Panel C illustrates the presence of a tumor island (red star) with palisading of nuclei (yellow arrow) and clefting (red arrow) on RCM, confirming the diagnosis of basal cell carcinoma (BCC). Panel D shows a dermatopathology slide of the lesion (8x), with a large basaloid nest containing hyperchromatic nuclei (red star), the presence of melanocytic pigment, and peripheral palisading nuclei (yellow arrow)

2. DISCUSSION

It has long been known that early detection of cutaneous malignancies is an important determinant in the morbidity considerations of a lesion. Numerous studies have illustrated dermoscopic features consistent with BCC and a small selection of studies have demonstrated features consistent with small‐sized BCC, though the features vary across cases. Implementing RCM in the screening of small‐sized skin lesions with the presence of pigment enhances the potential for in‐vivo detection of malignancies and differentiation between melanocytic lesions and BCCs as in these examples. Pereschino et al. wrote that the combination of RCM and dermoscopy is the “correct” way to screen microscopic pigmented lesions. ¹² We utilized these two imaging modalities to detect pigmented small‐sized BCC in three cases, each with a lesion diameter of 2 mm or less. Each of the three cases exhibited different dermoscopic features, reinforcing the dermoscopic variability of pigmented small‐sized BCC. Augmenting our examination with RCM enabled visualization of features and structures characteristic of BCC and resulted in the subsequent diagnosis of pigmented micro‐BCC. We therefore propose to define a micro‐BCC as a BCC with a diameter equal to or less than 2 mm. The growing body of literature on small‐sized BCC shows its prevalence and importance for its distinction from other cutaneous carcinomas. Our hope is that by publishing our findings, we can aid clinicians in accurate diagnosis of skin cancer in its earliest form, define micro‐BCCs, and reduce excessive biopsies of benign small‐sized pigmented lesions.

CONFLICT OF INTEREST

The authors declare that they have no conflict of interest.

FUNDING INFORMATION

None.

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.