Differentiating Early Stage Cystic Keratoacanthoma, Nodular Basal Cell Carcinoma, and Excoriated Acne Vulgaris by Clinical Exam, Dermoscopy, and Optical Coherence Tomography: A Report of 3 Cases

Abstract

Making accurate diagnoses when certain lesions are in a relatively young stage can prove challenging, as their “textbook descriptions” are often not fully apparent, and may in fact be markedly different. The authors present three interesting cases of early lesions that were clinically difficult to differentiate from one another: a cystic variation of a keratoacanthoma squamous cell carcinoma, a basal cell carcinoma, and an excoriated facial acne vulgaris. The subtle clinical nuances found in each of these cases demonstrated the importance of a careful clinical evaluation; however, this was not sufficient for adequate assessment of whether or not to biopsy. With early lesions such as these, the use of the noninvasive imaging modalities of dermoscopy and optical coherence tomography becomes critical in order to avoid unnecessary biopsy. The discussion of the clinically and dermoscopically challenging features is both instructive and enlightening. Oftentimes, “textbook descriptions” of lesions focus on the description of an already mature stage of growth, despite the fact that we continue to strive toward earlier detection of potential malignancies. With this in mind, the features found with optical coherence tomography proved essential to the elucidation of these difficult lesions. These three interesting cases illustrated the challenges encountered when dealing with early lesions specifically. The authors bring to light features in each of these cases that are often not thought of as being the “typical” presentation in each lesion category and demonstrate the clinical utility of noninvasive devices in difficult-to-diagnose cases such as these.

The authors report a three-case series of relatively early lesions that were clinically difficult to differentiate from one another: a cystic variation of a keratoacanthoma squamous cell carcinoma, basal cell carcinoma, and excoriated facial acne vulgaris. Differentiating these three lesions, specifically during their early development, can be challenging but possible after a careful clinical evaluation, followed by dermoscopy and optical coherence tomography (OCT) where appropriate. The authors present three cases illustrating the potential difficulties in achieving the appropriate diagnosis, as well as presenting the utility of current and new noninvasive diagnostic tools.

CASE SERIES

Patient 1. Squamous cell carcinoma (SCC), the second most common cutaneous malignancy, can present with various morphologies, including a keratoacanthoma (KA) type morphology.1 Patient 1 presented with a small, erythematous, nodular lesion on his leg that had developed within the past two weeks (Figure 1). KA-type SCCs are rapidly growing keratocytic epithelial tumors, almost exclusively found on sun-damaged skin—face, neck, chest, hands, arms, and legs.2 They appear as nodular, erythematous lesions that are either dome-shaped early on or crater-like later on in development (Figure 1). Often patients say that they thought the lesion was a bug bite, acne, or a cyst because of its rapid growth. They tend to be firm to palpation with central crusting as they enlarge or develop and can reach up to 3cm in size.2 Additionally, patients also describe them as being tender. Because of its small size and lack of central crusting, the patient’s lesion was clinically difficult to differentiate from other cystic lesions; however, its location on the sun-exposed leg was clinically consistent with a KA-type SCC. Dermoscopic features lent additional information and confirmed the need for biopsy.

Figure 1.

Patient 1: Clinical and dermoscopic findings of cystic-variant KA-type SCC with central crust mimicking puncture of acne compared to typical keratoancanthoma with central keratin crust and peripheral keratinizing (looped) vessels. Schematic figure of peripheral looped vessels.

The dermoscopic features of KA-type SCC include a pink and/or white, shiny background with central crusting and the presence of peripheral looped hairpin vessels (Figure 1). In this patient’s case of a cystic-variant KA-type SCC, the central, pinpoint, white crust seemed to mimic that of a punctum seen in acneiform lesions (Figure 4) or even in the subsequent case of a nodular basal cell carcinoma (BCC) (Figure 2). The diagnosis of a cystic variant SCC KA-type was confirmed with biopsy.

Figure 4.

Patient 3: Clinical and dermoscopic findings of excoriated acne vulgaris lesion. Upper right: This example illustrates the localized yellow hue that can be seen in an ulcerated BCC.

Figure 2.

Patient 2: Clinical and dermoscopic findings of nodular BCC with central punctum-like crust and radial thin sharp arborizing vessels compared to typical basal cell with sharp arborizing vessels crossing the mid-line. Radial crowning of vessels seen in sebacious hyperplasia.

Patient 2. BCC, the most common cutaneous malignancy on persons with skin types I to III, can also present with various morphologies, including nodular BCC. The classic nodulocystic BCC is clinically described small, 2 to 3mm, pearly papule with arborizing vessels found most frequently on sun-damaged skin2 (Figure 2). Patient 2 presented with a very small, symptomatically unremarkable, nodular, flesh-colored to slightly pearly papule that had developed in the previous month (Figure 2). The authors’ findings on dermoscopy were also challenging.

The typical dermoscopic features of a nodular BCC include a pink/flesh-colored, shiny or translucent background with arborizing vessels and sometimes crust (Figure 2). In our patient’s BCC case, the central location of the crust, similarly to patient l’s cystic SCC KA-type lesion, mimicked the punctum seen in cystic/acneiform lesions. Further, the radiating appearance of the vessels imitated the radial crowning of vessels seen in sebaceous hyperplasia or cystic acneiform papules (Figure 2). OCT was used to better determine whether biopsy was necessary.

OCT is a noninvasive option to better differentiate difficult-to-diagnose lesions. The OCT revealed well-defined, circumferential, grape-cluster-like, hypo-reflective (darker/shadow) areas, which represent tumor islands similar to what one would see with an H&E biopsy (Figure 3). This eliminated the doubt that it may be an excoriated acne lesion and confirmed the need for biopsy, which confirmed nodular BCC.

Figure 3.

OCT of BCC versus excoriated acne. In the above picture of a BCC, the hypo-reflective/shadow, circumferential areas represent tumor islands seen on H&E. The nonspecific, disorganized hypo-reflection seen around hair follicles is clear in this example of acne vulgaris.

Patient 3. Acne vulgaris, the most common skin disease in the United States, can, similarly to the previously discussed lesions, present in different morphologies.2 While typically seen more often in adolescents and young adults, older populations still experience acne lesions from comedones to large, tender nodules and cysts. The erythematous papules and nodules if picked and inflamed can be difficult to differentiate from some presentations of early BCC’s in fare-skinned, older adults. Patient 3 presented with an inflamed, flesh-colored, slightly pearly papule that had developed over the past few weeks on the nose (Figure 4). The patient was concerned of a potential carcinoma because it kept bleeding and did not seem to heal. The age of the patient and location and appearance of the papule combined with the history of bleeding placed an early BCC in the differential diagnosis.

Dermoscopic features of acne lesions can include a neutral yellow background and the previously discussed central punctum. The dermoscopy of this lesion revealed a neutral yellow background with arborizing-like vessels (Figure 4). The neutral yellow background is indicative of an acneiform lesion; however, when the lesion is excoriated, this can often be difficult to differentiate from the yellow ulceration of a BCC (Figure 4). Further, the arborizing-like vessels and lack of punctum were again consistent with the authors’ suspicion of this potentially being a BCC. OCT was used to further elucidate their findings.

The OCT revealed non-specific, ill-defined hypo-reflection (dark/ shadow) areas around follicular openings (Figure 3). No evidence of any well-defined, circumferential tumor-islands were present, thus eliminating BCC from the authors’ differential and clarifying that this was in fact an excoriated AV lesion.

CONCLUSION

These three interesting cases illustrated the challenges encountered in confidently narrowing down the differential to an accurate diagnosis when dealing with early lesions specifically. The authors have demonstrated the value of using dermoscopy and OCT in light of clinical observations in order to determine whether biopsy is needed in difficult lesions such as these.