What is fibroepithelioma of Pinkus?
Fibroepithelioma of Pinkus, also known as Pinkus tumour and Pinkus epithelioma, is a premalignant fibroepithelial tumour that was first described by Hermann Pinkus in 1953 . Originally classified as a rare variant of basal cell carcinoma (BCC), a malignant neoplasm, it has since been controversially reclassified as a trichoblastoma, a benign neoplasm [2–4].
Clinically, fibroepithelioma of Pinkus may resemble a range of benign skin tumours that are not routinely excised .
Who gets fibroepithelioma of Pinkus?
There are few reported cases and little epidemiological data for fibroepithelioma of Pinkus. This may be due to its similarity to benign skin lesions, resulting in the rarity of its diagnosis .
Fibroepithelioma of Pinkus is diagnosed mainly in fair-skinned women and it is most frequently located in the lumbosacral region, although it may occur anywhere on the skin [5,7]. It typically develops between 40 and 60 years of age, although there have been paediatric case reports of its occurrence [8,9].
What causes fibroepithelioma of Pinkus?
The pathogenesis and genetic basis of fibroepithelioma of Pinkus are not yet fully understood. Although the mechanisms may be similar to the development of BCC, chronic ultraviolet damage seems to be a lesser factor in fibroepithelioma of Pinkus, as these tumours do not commonly develop in areas that are routinely exposed to the sun [3,5].
A previous study with mice has shown that mutations in the PTCH transmembrane regulator gene in the Hedgehog signalling pathway may be involved in the development of fibroepithelioma of Pinkus . Further studies are required to determine PTCH mutations also play a role in its development in humans. In addition, there have been reports of fibroepithelioma of Pinkus arising in skin sites after radiation therapy, although a direct relationship is yet to be defined .
What are the clinical features of fibroepithelioma of Pinkus?
Fibroepithelioma of Pinkus typically presents as a single, erythematous or flesh-coloured, dome-shaped papule or plaque. Large pedunculated, ulcerated, cystic, and pleomorphic variants with different pigmentation combinations have also been reported [5,7].
Unlike in BCC, there have been no reports of spontaneous bleeding in fibroepithelioma of Pinkus.
What are the complications of fibroepithelioma of Pinkus?
Fibroepithelioma of Pinkus is not known to result in further complications or malignancy. It has rarely been associated with other malignancies, such as breast carcinoma, mammary Paget disease, and gastrointestinal tumours [12–14].
How is fibroepithelioma of Pinkus diagnosed?
While a clinical examination is unlikely to lead to a diagnosis of fibroepithelioma of Pinkus, due to its similarity to benign lesions, dermoscopy can be helpful in diagnosis . The following dermoscopic patterns are seen in fibroepithelioma of Pinkus [3,6,15]:
- Polymorphous vessels with mainly fine arborising and peripheral dotted vessels
- White streaks under polarised dermoscopy (also called chrysalis/crystalline structures) similar to those in BCC
- Milia-like cysts and ulceration (these are reported in but not specific for fibroepithelioma of Pinkus)
- Grey-brown pigmentation and grey-blue dots (in pigmented fibroepithelioma of Pinkus).
The gold standard diagnostic test for fibroepithelioma of Pinkus is a skin biopsy taken for histopathological examination. Fibroepithelioma of Pinkus is characterised by interconnected, branching strands of basaloid cells embedded by a loose, richly vascularised fibrous stroma, extending from the epidermis down into the dermis [3,16].
What is the differential diagnosis for fibroepithelioma of Pinkus?
Fibroepithelioma of Pinkus is typically mistaken for the following benign skin lesions:
- An acrochordon — this normally has a narrower base and lacks erythema
- A dermal melanocytic naevus — this lacks erythema and is rarely pedunculated
- A solitary neurofibroma — these are usually more compressible and lack erythema
- A seborrhoeic keratosis — this has a more waxy or warty surface and is rarely pedunculated
- A haemangioma — this lacks pedunculation and has a more uniform, deeper erythema.
What is the treatment for fibroepithelioma of Pinkus?
The definitive treatment for fibroepithelioma of Pinkus is surgical excision with 4-mm margins, as is indicated for BCC . Electrodessication and curettage or Mohs micrographic surgery could be considered in higher-risk locations, such as the head and neck, or in large tumours [3,7].
Medical topical treatments, such as imiquimod, are ineffective for fibroepithelioma of Pinkus despite their role in the treatment of superficial BCC . There is no role for chemotherapy or radiation.
What is the outcome for fibroepithelioma of Pinkus?
Fibroepithelioma of Pinkus is generally considered to have an indolent course with no metastatic potential [7,8]. It has never been reported to result in patient death .