Clinical and Dermoscopic Features of Fibroepithelioma of Pinkus: Case Series with an Emphasis on Hypopigmented to Pink Lines Intersecting at Acute Angles (2025)

Abstract

Fibroepithelioma of Pinkus (FEP) is a subtype of basal cell carcinoma (BCC) that can clinically resemble intradermal nevi (IDN) and fibromas. We performed a retrospective review of consecutively biopsied lesions confirmed to be FEP on histopathology diagnosed from January 1, 2008 to April 8, 2019. Clinical (n = 48), contact non-polarized dermoscopy (NPD) (n = 44), and contact polarized dermoscopy (PD) (n = 22) images from 36 patients were reviewed. Mean age was 64.5 years (SD 15.1 years, range 24–86 years) at diagnosis of first FEP lesion. Most lesions were located on the torso (n = 28, 58.3%), followed by the lower extremity (n = 9, 18.8%). The most common differential diagnoses at time of biopsy included BCC (n = 40) and nevus (other than IDN, n = 5). Clinically, FEP were pink (95.8%), scaly (66.7%) papules (77.1%) displaying disrupted skin markings (62.5%) and absence of hair follicles (87.5%). NPD revealed serpentine (97.7%), dotted (81.8%), or polymorphous vessels (86.4%), and hypopigmented to pink lines intersecting at acute angles (HPLA) (52.3%). PD demonstrated serpentine (95.5%), dotted (86.4%), or polymorphous vessels (81.8%), shiny white lines (50.0%), and HPLA (59.1%). Classic features of BCC such as arborizing vessels (n = 2), ulceration (n = 1), shiny white blotches and strands (n = 1), blue-gray ovoid nest (n = 1), and leaf-like areas (n = 1) were uncommon. FEP often presents as scaly, erythematous papules with disrupted skin markings and absence of hair follicles. Dermoscopy reveals polymorphous vessels with shiny white lines and HPLA.

Keywords: Fibroepithelioma of Pinkus, dermoscopy, basal cell carcinoma, polymorphous vessels, shiny white lines

Introduction

Fibroepithelioma of Pinkus (FEP) is a relatively indolent subtype of basal cell carcinoma (BCC) that was first described by Herman Pinkus in 1953.[12,6] While some debate exists as to whether FEP is a bona fide BCC or a fenestrated variant of trichoblastoma,[4,18,19,7] clinicians often manage the lesion as a BCC. Many cases of FEP (72%) are diagnosed in individuals who are 51 years of age or older[4] and FEP comprises less than 2% of all BCC subtypes.[2,15,3] FEP is often found on the torso with a lumbosacral predilection[4,3] as a flesh-colored to pink nodule, plaque, or papule,[12,16] but pigmented varieties have also been reported.[1,6] The differential diagnosis for tumors that prove to be FEP includes intradermal nevus, pedunculated fibroma, seborrheic keratosis, and melanoma.[1,16] Histologically, FEP is characterized by anastomosing epithelial strands traversing and separating a fibrous stroma.[12] This histologic pattern was postulated to be due to the spread of BCC along eccrine ducts and replacement of ducts with BCC strands.[20]

Dermoscopy may serve as a valuable tool to diagnose FEP and differentiate it from benign tumors, such as intradermal nevi and fibromas. Previous case reports and small case series have shown that FEP manifests a polymorphous vessel pattern than can include fine arborizing vessels, linear vessels, and dotted vessels.[22,24,21] In addition, FEP often reveals white streaks/striae/septal lines that are believed to correspond to fibrosis on histology.[22,24] Many of these same features have also been described in melanoma. However, limitations of previous studies are their lack of descriptors for the primary clinical morphology of FEP and their small sample sizes as highlighted by the fact that the largest previous case series that described dermoscopic features of FEP was limited to 10 cases.[22] We conducted this study to elucidate the clinical and dermoscopic morphology of FEP in a large case series of patients and to determine if they possess features that are uniquely different from the known features described for other lesions that may appear on the differential, including other subtypes of BCC, benign nevi, and melanoma.

Methods

Institutional Review Board approval was obtained for this retrospective study involving the review and study of existing data. We reviewed cases of histopathology-confirmed FEP diagnosed at our institution from January 1, 2008 to April 8, 2019 with pathology reports containing the terms “fibroepithel” or “pinkus.” The pathology reports were reviewed and only those with a diagnosis of FEP were included. We retrieved clinical, contact non-polarized dermoscopy (NPD), and contact polarized dermoscopy (PD) images of all cases. We excluded collision tumors and tumors without any images. In addition, poor quality clinical and dermoscopic images (overexposed, underexposed, or out of focus) were excluded. Clinical, contact NPD, and contact PD images were reviewed by at least three clinicians experienced in dermoscopy and the presence or absence of clinical and dermoscopic features was agreed upon via consensus. We distinguished between shiny white lines, which are short, thin white lines oriented parallel and orthogonal to each other, and shiny white blotches and strands, which are white structureless areas, ovals, or circular structures and poorly defined lines arranged in parallel or haphazardly, respectively. We also employed the phrase “hypopigmented to pink lines intersecting at acute angles” (HPLA) to describe lines surrounding pink vascular holes. The hypopigmented to pink lines themselves are devoid of any structures, including vessels. Based on prior experience, we created this new phrase because the HPLA noted in this study appear to represent a feature that is distinct from the previously described negative network and shiny white lines. HPLA is in contrast to the negative network that describes brown curvilinear, elongated structures that are surrounded by relative hypopigmentation which can appear as serpiginous lines.[11,13]

Manual chart review was performed to determine patient demographics, anatomic site, and differential diagnosis rendered at time of biopsy. Descriptive statistical analysis was performed for patient demographics while relative frequencies were calculated for anatomic site, clinical features, and dermoscopic features.

Results

A total of 48 lesions with associated clinical images met our inclusion criteria, of which 44 lesions had associated contact NPD images and 22 lesions had associated contact PD images. These 48 lesions were biopsied from 36 patients, 22 of whom were male (61.1%). The mean age was 64.5 years (SD 15.1 years, range 24 to 86 years) at the time of diagnosis of each patient’s first FEP lesion. Anatomic site (Table 1) and differential diagnosis at time of biopsy (Table 2) were noted. Representative FEP lesions with clinical, dermoscopic, and histopathologic images are depicted in Figures 1 and ​and22.

Discussion

We report the clinical and dermoscopic features of FEP in a large series of patients. Clinically, these lesions often presented as pink, scaly papules with disruption of skin markings and absence of hair follicles. A feature that has not been highlighted before in other studies was the presence of scale, which was found in 66.7% of our cases of FEP and differs from nodular basal cell carcinomas which often have a shiny, non-scaly surface. Another feature that differentiates FEP from nodular BCC is the conspicuous absence or near absence of arborizing vessels in the former. Instead, dermoscopy of FEP revealed a high frequency of polymorphous vessels with the most frequent vessel subtypes being serpentine vessels and dotted vessels. In addition, FEP often lacked shiny white blotches and strands which are another well-characterized feature of other BCC subtypes. Instead, shiny white lines were prominent in FEP. The presence of polymorphous vessels and shiny white lines in FEP can therefore result in a differential which includes melanoma.

Observations made in our study and experience of one of the authors (A.A.M.) raises an important point that is worthy of discussion regarding the dermoscopic terminology used to describe the so-called negative network. The classic negative network seen on both polarized and non-polarized dermoscopy describes brown curvilinear, elongated globular structures situated on background skin of lighter color compared to the globular structures (Figure 3A). If one focuses on the lighter background instead of the globular structures, the background can take on the appearance of serpiginous hypopigmented lines.[11,13] Other terms have been used synonymously with negative network including inverse network, white network, and reticular depigmentation and in the last terminology consensus meeting it was decided to group inverse network and reticular depigmentation under the term negative network.[8,23] However, it now appears highly probable that there are at least three different entities with different histopathology correlations that are grouped under the term negative network. Some have previously attempted to describe different subtypes of negative network with type A corresponding with globular structures and type B with dotted vessels in the holes of the network.[14] While these earlier observations did not gain traction, it has become increasingly apparent that there are indeed multiple different entities that are collectively grouped under the term negative network. Here we make a distinction between them and conclude that the term negative network should be exclusively used to describe the classic negative network elucidated above as a feature seen in melanocytic neoplasms, only (Figure 3A). The dermoscopic hypopigmented lines of the negative network correlate histopathologically with widened rete ridges and between these widened rete ridges there are multiple smaller, distorted rete ridges containing atypical melanocytes. These shorter distorted rete ridges correspond to the brown elongated globular structures seen with dermoscopy.[5]

This classic negative network is distinctly different from a pattern of shiny white lines which unlike the classic negative network can only be seen with PD.[10] These shiny white lines can meet at acute angles to form rectangles, with squares being most common (Figure 3B). The histopathology of these shiny white lines corresponds with collagen[10] and may best be classified as shiny white network lines. We have noted these shiny white lines forming rectangles in various lesions, such as melanoma, dermatofibroma, and Spitz nevi. The second pattern that is distinctly different from the classic negative network is the pattern we see in FEP. It consists of hypopigmented to pink lines intersecting at acute angles (HPLA) as seen in Figures 1, ​,2,2, ​,3C,3C, ​,3D.3D. This pattern may in fact correspond to what was called reticular depigmentation. The lines themselves are devoid of any structures or vessels within them and they surround pink vasculature structures. This pattern can be seen with both PD and NPD along with occasional overlap with shiny white lines on PD. We have observed this pattern in FEP, hypopigmented melanoma, and Spitz nevi. Close inspection will reveal that these two dermoscopic patterns are distinct from the classic negative network (Table 5).

Based on review of the literature, we believe that hypopigmented to pink lines intersecting at acute angles (reticular depigmentation) in our study are similar to the negative network[21] and white network[9] that were previously reported on dermoscopic examination of FEP. In FEP, it is likely that the darker pink holes surrounded by HPLA correlate with vessels within a fibrotic stroma on histology. Meanwhile, the hypopigmented to light pink lines likely correspond to epithelial tumor strands that emanate from the epidermis in FEP, a pattern which can be seen in Figures 1D and ​and2D.2D. Future research should further investigate the histopathologic correlates of these hypopigmented to pink lines on dermoscopy.

Our study is limited by its retrospective design and the presence of few pigmented FEP lesions. The latter may account for the frequent lack of leaf-like areas and blue-gray ovoid nests in our series, which are features often associated with pigmented BCC.[17] In fact, a leaf-like area was only described in one of two FEPs that were pigmented as per pathology reports in our study. However, the lack of other common features of BCC, including arborizing vessels and shiny white blotches and strands,[17] suggests that the dermoscopic features of FEP are often distinct from those of other BCC subtypes.

In conclusion, Fibroepithelioma of Pinkus lesions are often clinically pink, scaly papules devoid of hair and can have a broad clinical differential diagnosis including basal cell carcinoma and nevus. On dermoscopy, there is a paradox in that these tumors tend not to manifest the known features of basal cell carcinoma such as arborizing vessels and shiny white blotches and strands. Instead, they tend to manifest features more commonly associated with melanoma, including polymorphous vessels and shiny white lines. A diagnosis of FEP should be strongly considered when one encounters raised, scaly, hairless lesions that lack common features of BCCs or intradermal nevi on dermoscopy and instead reveal polymorphous vessels, shiny white lines, and hypopigmented to pink lines intersecting at acute angles.

Funding: Funding/Support:

This work was funded in part through the National Institutes of Health/National Cancer Institute Cancer Center Support Grant P30 CA008748

Footnotes

References