Nonpigmented Adenoid Subtype of Basal Cell Carcinoma: A Case Report

Abstract

Introduction

Basal cell carcinoma (BCC) is the most common skin cancer, with a rising incidence globally. We encountered a patient with the nonpigmented adenoid subtype of BCC. The nonpigmented subtype of BCC accounts for only a small percentage of cases of BCC in the Asian population, with the adenoid subtype of BCC also being rare in all human ethnicities.

Case Presentation

An 82-year-old woman presented to us with a growth in the inner canthus of the left eye, which had been slowly evolving for about 1 year. The lesion had failed to respond to a variety of topical treatments. Physical examination revealed a reddish plaque in the inner canthus of the left eye that measured 10 × 6 mm in size. Dermoscopic evaluation showed blue-gray globules and arborizing telangiectasia. Histopathological examination confirmed the diagnosis of adenoid BCC.

Conclusion

We analyzed the data of patients with the adenoid subtype of BCC in the Japanese population and found the possibility that this variant of BCC was often nonpigmented. Furthermore, we collected the dermoscopic findings of patients with the adenoid subtype of BCC; however, the data revealed no other noteworthy characteristics at present. We expect that further characterization of these two variants of BCC through accumulation of data from clinical cases will contribute to facilitating early diagnosis.

Introduction

Epidemiological data indicates that the overall incidence of basal cell carcinoma (BCC) is increasing worldwide [1]. Among the major causes can be the increase in the percentage of the elderly population, as well as the increase exposure of the human population to ultraviolet radiation due to ozone layer depletion [1]. BCC is the most common skin cancer for Caucasians, Hispanics, and Asians. Clinically, 88.3% of all BCCs in the Japanese population showed pigmentation [2], as compared with 6% of BCC cases in Caucasians [3]. According to a report from Korea, BCC lesions were pigmented in 77.1% [4]. Therefore, pigmentation may be the most characteristic clinical feature of BCC in Asian patients. The adenoid subtype is a rare histological variant of BCC with a reported incidence rate of 1.3%–20.9% [5]. It is considered to be a rare subtype of nodular BCC and as a low-grade malignancy as compared with other BCC variants [6, 7]. On the other hand, a recent case-control study reported that adenoid BCC might be associated with a higher recurrence rate as compared with other low-risk BCCs [8]. We encountered a patient with the nonpigmented adenoid subtype of BCC. In this clinical case, diagnosis based on the clinical features and dermoscopic findings was difficult, and definitive diagnosis was achieved by skin biopsy. We collected the dermoscopic findings of patients with the adenoid subtype of BCC herein.

Case Report

An 82-year-old woman presented with a growth in the inner canthus of the left eye which had been slowly evolving for about 1 year. She had been seen by several ophthalmologists and dermatologists and been prescribed antibiotic, corticosteroid, and tacrolimus ointments for topical use. However, the lesion failed to show improvement. The patient’s past medical history included aortic regurgitation and angina pectoris. Physical examination revealed a reddish plaque in the inner canthus of the left eye that measured 10 × 6 mm in size (Fig. 1). The initial differential diagnoses included seborrheic keratosis, actinic keratosis, and Bowen’s disease. Dermoscopic evaluation showed blue-gray globules and arborizing telangiectasia (Fig. 2). Biopsy from the lesion revealed masses in the dermis and divided spaces separating them from the connective tissue (Fig. 3a). The masses of basaloid cells showed peripheral palisading with pleomorphism and mitotic activity. At places, the cells showed tubular differentiation with the lumina found to be filled with an amorphous granular material (Fig. 3b). Histopathological examination confirmed the diagnosis of adenoid BCC. Cutaneous adenoid cystic carcinoma was considered as a differential diagnosis. It is a rare skin tumor that can closely mimic adenoid BCC on histology. The tumor shows strongly positive immunohistochemical staining for C-kit; however, our case showed negative staining for it. Cutaneous apocrine carcinoma could be another differential diagnosis. It is composed of neoplastic glands in the dermis arranged in a predominantly cribriform pattern. The cells show apocrine differentiation in the form of large round to polygonal cells with abundant eosinophilic granular cytoplasm. The lesion in our case failed to show apocrine differentiation. We performed resection with a 5-mm margin, while preserving the orbicularis oculi muscle. The resulting skin defect was temporarily covered with artificial dermis. After confirmation of pathological negative margins, an orbicularis oculi muscular pedicle musculocutaneous island flap was designed above the skin defect, and a cheek flap was designed below the skin defect. No evidence of recurrence has been noted until the present, 13 months since the surgery.

Fig. 1.

Reddish plaque in the inner canthus of the left eye that measured 10 × 6 mm in size.

Fig. 2.

Dermoscopic evaluation showed blue-gray globules and arborizing telangiectasia.

Fig. 3.

a Masses of tumor cells separated by stroma (H&E stain, ×100). b Basaloid cells arranged in sheets, islands, and trabecular pattern with palisading nuclei (H&E stain, ×400).

Discussion

Dermoscopy in cases of pigmented BCC shows no pigment network, with one or more of the following six findings: large blue-gray ovoid nests, arborizing vessels, multiple blue-gray globules, ulceration, leaf-like areas, and spoke-wheel areas [9]. The dermoscopic findings in cases of nonpigmented BCC are characterized by the absence of pigmented lesions, arborizing telangiectasia, ulceration, short fine superficial telangiectasia, and multiple small erosions [9]. In the present case, dermoscopic examination revealed blue-gray globules and arborizing telangiectasia. Takenouchi and Takahashi reported that a higher complete excision rate in cases of pigmented BCC than in those of nonpigmented BCC [2]. This difference is due, of course, to the more distinct boundaries that can be observed in cases of pigmented BCC.

Clinically, adenoid BCC lesions can appear as pigmented or nonpigmented nodules or ulcers at various sites including the axillae, back, legs, inner canthus of the eyes, chin, and forehead [10]. Histologically, the lesion composes of small uniform cells with peripheral palisading nuclei arranged in nests and cords with intertwining stands and radially around islands of connective tissue, resulting in a tumor with a lace-like pattern. The lumina may be filled with a colloidal substance or with an amorphous granular material [10].

The reported prevalence of adenoid BCC in a study of 256 Japanese cases was 9.8% [11]. This information was derived from a report from departments of anatomy, but the report did not include any description about BCC recurrence or color. However, there were Japanese case reports covering 12 cases of adenoid BCC over the past 3 decades. According to these reports, recurrence after resection occurred only 1 (8.3%) case, and the adenoid BCC was nonpigmented in 3 (30.0%) of the 10 cases for which information about the color was available. This percentage was high as compared with the previously reported 6.2% for nonpigmented lesions among Japanese patients with BCC [2]. We may therefore say that adenoid BCCs in the Japanese population are often nonpigmented, but the number of cases analyzed is still insufficient, and accumulation of data from further cases is essential.

The number of reports on the dermoscopic findings of adenoid BCC is still small. We summarized the dermoscopic features reported to date in Table 1. It is known that the histopathological type of BCC is difficult to determine solely on the basis of the dermoscopic findings [6]. According to our view, it is difficult at present to diagnose adenoid BCC, as it was in our own case, solely based on the dermoscopic findings, even if the diagnosis of BCC can be suspected based on such information alone.

Table 1.

Summary of dermoscopy findings of adenoid BCC

Dermoscopic feature	Reference number
	12	13	6	14	15	present case
Blue-gray ovoid nests					〇
Blue-gray dots and globules					〇	〇
Blue-gray discoloration			〇
Spok-wheel structures	〇
Arborizing telangiectasias		〇				〇
Short fine telangiectasia	〇				〇
Polymorphic vascularization				〇
Ulceration		〇
Shiny white structures		〇
Whitish veil					〇
Irregular white streaks			〇
Yellowish structure				〇
Hemorrhage				〇
Scale			〇

In the present case, we suspected a tumor, because the plaque had failed to improve even after more than 1 year of treatment with a variety of topical agents. Cases of nonpigmented adenoid subtype of BCC are difficult to diagnose based on the clinical and dermoscopic features alone. Skin biopsy may still be necessary for early diagnosis of refractory lesions. Accumulation of data about the color and dermoscopic findings of adenoid BCC among Asian people may allow identification of some specific characteristics, thus facilitating early diagnosis of this type of BCC.

Statement of Ethics

Ethical approval is not required for this study in accordance with local or national guidelines. Written informed consent was obtained from patient for publication of the details of their medical case and any accompanying images. The CARE Checklist has been completed by the authors for this case report, attached as online supplementary material (for all online suppl. material, see https://doi.org/10.1159/000551351).

Conflict of Interest Statement

The authors have no conflicts of interest to declare.

Funding Sources

This study was not supported by any sponsor or funder.

Author Contributions

Y.I. wrote original draft. S.N. and A.H. reviewed and edited the draft.

Funding Statement

This study was not supported by any sponsor or funder.

Data Availability Statement

All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.