Inverted follicular keratosis is not a specific keratosis but a verruca vulgaris (or seborrheic keratosis) with squamous eddies

Inverted Follicular Keratosis: A Rare Presentation in External Ear Canal

Inverted follicular keratosis is a benign skin lesion that typically presents as an asymptomatic, solitary nodule that may mimic malignant lesions, especially squamous cell carcinoma, both clinically and pathologically. It is developed from the hair follicle infundibulum and can be considered a variant of seborrheic dermatitis. We present a case of a 26-year-old gentleman with a soft tissue mass at the external auditory canal which was later confirmed as inverted follicular keratosis and was treated by endoscopic transcanal excision of the mass with temporalis fascia graft reconstruction. He is currently under surveillance follow-up with no symptoms and signs of recurrence.

Periocular inverted follicular keratosis: a retrospective series over 17 years

PURPOSE

To evaluate the demographic, clinical, and histopathologic characteristics of periocular inverted follicular keratosis (IFK), a very rare lesion with poorly defined characteristics.

STUDY DESIGN

Retrospective case series.

METHODS

We evaluated 11 patients with clinically diagnosed IFK confirmed by histologic analysis. Data were collected on the patients' demographics, clinical presentation and course of the disease, signs and symptoms, location of the lesion, and outcomes of treatment.

RESULTS

The patients' mean age was 71 years (range, 32-91 years). Seven (64%) of the patients were female. Eight of the patients (72.7%) had no symptoms, two (18.2%) reported itching, and one (9.1%) had edema and bleeding of the lesion. The lesion affected the upper eyelid in 4 of the patients (36%), the lower lid in 3 of the patients (27%), and the inner canthus in 4 of the patients (36%).

CONCLUSIONS

IFK has no specific clinical characteristic and thus requires histologic confirmation for its diagnosis and appropriate management.

Reflectance confocal microscopy of an inverted follicular keratosis mimicking a squamous cell carcinoma

Distinguishing between benign and malignant neoplasms of the skin is a daily challenge to dermatologists. With the use of a dermatoscope and other imaging devices, the diagnosis is often more precise. The confocal microscope is a device that uses a near-infrared laser to perform noninvasive imaging of the skin. The benefit is that the images immediately provide additional, cellular-level information that can assist in diagnosis. However, lesions may share overlapping characteristics on confocal microscopy, and hence, benign lesions can still display confocal features concerning for a cancerous process, justifying a biopsy. Here, we present a case of an inverted follicular keratosis imitating a squamous cell carcinoma on confocal microscopy.

Inverted follicular keratosis successfully treated with imiquimod

Inverted follicular keratosis is a rare benign tumor of the follicular infundibulum characterized by exo-endophytic growing. It is thought to be a rare variant of the seborrheic keratosis. The diagnosis of inverted follicular keratosis is generally established histopathologically because clinical differentiation from other lesions is difficult. Herein, we present one such rare case, successfully treated with topical 5% imiquimod cream.

Clinicopathological features of eyelid skin tumors. A retrospective study of 5504 cases and review of literature

Eyelid tumors are the most common neoplasm in daily ophthalmology practice and encompass a wide variety of benign and malignant tumors. In this retrospective study, we report the clinical and histological features of 5504 eyelid skin tumors diagnosed at the Laboratory of Ophthalmopathology of the Hôpital Ophtalmique Jules Gonin, Lausanne, Switzerland, between January 1989 and December 2007. Benign tumors largely predominated over malignant ones, representing 84% of cases in this series, and the 5 most frequent subtypes were squamous cell papilloma (26%), seborrheic keratosis (21%), melanocytic nevus (20%), hidrocystoma (8%), and xanthoma/xanthelasma (6%). Basal cell carcinoma was the most frequent malignant tumor (86%), followed by squamous cell carcinoma (7%) and sebaceous carcinoma (3%). For several tumor subtypes, there was a poor correlation between clinical and histological diagnosis, stressing the numerous pitfalls in the diagnosis of eyelid tumors. We further discuss our results with reference to previously published series.

An assist to the next (10th) edition of Lever's Histopathology of the Skin

Lever's Histopathology of the Skin, regarded as the gold standard textbook in the field of dermatopathology, claims to cut a swath through the discipline. In the last two editions, however, it appears to be declining in its overall scientific quality and academic mentality by failing to include different points of view set forth by other authors. Some ideas of a single author, coupled with appropriate references, are offered by me now for consideration for inclusion in the next (10th) edition of Lever's text.

Inverted follicular keratosis simulating malignant melanoma

A 93-year-old woman was noted to have a single pigmented lesion on the posterior aspect of her neck. Clinical examination revealed a 12 x 8-mm flat lesion, with an irregular border and variegated pigmentation. Dermatoscopic examination revealed a lesion with multiple colours, featureless areas and black dots, suggestive of malignant melanoma. With a presumed clinical diagnosis of malignant melanoma, an elliptical excision was performed, with a 1-cm margin. However, histological examination revealed the unexpected diagnosis of pigmented inverted follicular keratosis.

Squamous Eddies in Irritated Seborrheic Keratosis

Seborrheic keratosis is related to the intraepidermal hair follicle in its morphogenesis. Squamous eddies in irritated seborrheic keratosis (ISK) are known to develop by focal maturation of basaloid cells, but the significance of squamous eddies is not understood. The purpose of this study was to elucidate the nature of squamous eddies in ISK. Serial sections of paraffin blocks of 20 cases of ISK were examined. We tracked each squamous eddy through the serial sections to observe the different shapes and positions of the same squamous eddy. In 4 cases, squamous eddies revealed hair shafts at their centers in different sections. In 14 cases, squamous eddies contained acrotrichial canals. In 13 cases, squamous eddies were connected to keratotic invaginations we thought to be follicular infundibula. Eighteen of the 20 cases of ISK showed at least 1 of the morphological features of intraepidermal hair follicle structures. We have found that the squamous eddies of ISK are anatomically related to acrotrichia.

Bcl-2-positive epidermal dendritic cells in inverted follicular keratoses but not squamous cell carcinomas or seborrheic keratoses

AIM

In our previous research, bcl-2-positive dendritic cells were seen in increased numbers in suprabasal areas of inverted follicular keratoses (IFKs) compared to seborrheic keratoses (SKs). The purpose of this study was twofold; firstly, to support that these dendritic cells are Langerhans cells and secondly, to contrast the epidermal dendritic cells in IFKs, squamous cell carcinomas (SCCs), and SKs.

METHODS

Ten IFKs and five SKs previously showing bcl-2-positive dendritic cells within the epidermis were stained with CD1a. Fifteen other IFKs were stained with CD1a alone. Ten SCCs were stained with bcl-2 and CD1a.

RESULTS

In the 10 IFKs stained with both bcl-2 and CD1a, the density of CD1a-positive cells correlated well with the density of bcl-2-positive dendritic cells; in the five SKs, the density of CD1a-positive cells was similar to that seen in IFKs but was higher compared to the density of bcl-2-positive dendritic cells in SKs (p < 0.05). The IFKs had a significantly higher number of CD1a-positive cells compared to SCCs (p < 0.01). SCCs showed bcl-2-positive cells only within the basal layer of the normal epidermis flanking the carcinomas.

CONCLUSIONS

These results suggest that there is different bcl-2 regulation of CD1a-positive cells in IFKs, SKs, and SCCs.

Benign keratosis with a spectrum of follicular differentiation: a case series and investigation of a potential role of human papilloma virus

BACKGROUND

A variety of dermatopathologic entities are histologically defined by the presence of follicular differentiation. Follicular differentiation confined to the epidermis may follow induction from dermal mesenchymal proliferations, as in a nevus sebaceus of Jadassohn, or represent endogenous proliferations such as the tumor of the follicular infundibulum or trichilemmoma.

METHODS

We report on five cases of a histologically distinct form of benign keratosis showing variable follicular differentiation. Clinicopathologic correlation and analysis of a potential human papilloma virus pathogenesis was investigated.

RESULTS

Each of the cases arose on the trunk or extremities of three men and two women with a mean age at presentation of 66.6 years. All of the lesions showed variable follicular differentiation, with germinative basaloid cells, matrical cells with matrical keratinization, inner root sheath with trichohyalin granules, or glycogenated lower outer root sheath. Immunohistochemical staining for human papilloma virus was negative in each case.

CONCLUSIONS

There exists a distinct entity, histologically defined as a keratosis with variable follicular differentiation, which has not been previously described. These lesions do not appear to be pathogenically related to human papilloma virus infection.

Eccrine or apocrine poroma? Six poromas with divergent adnexal differentiation

We describe six cases of benign eccrine poroma-like neoplasms with divergent adnexal differentiation. Four cases exhibited sebaceous differentiation in the form of individual or clustered sebocytes with or without sebaceous ducts. One case showed both sebaceous and hair follicle differentiation, and one case showed sebaceous and possible apocrine secretory differentiation. Clinically, most were skin-colored, red, or purple papules or nodules. One patient had a preoperative diagnosis of Bowen's disease, with an erythematous plaque. None recurred following biopsy. Previous reports of similar lesions have suggested a possible role for human papilloma virus (HPV) in their pathogenesis; however, immunohistochemical staining for HPV structural antigens was negative in all six of these cases. Similarities to previously reported cases of eccrine poroma-like neoplasms with sebaceous differentiation are discussed. Given the evidence of sebaceous and follicular differentiation seen in this study and the common embryologic origin of follicular, sebaceous, and apocrine structures, it follows that at least some benign neoplastic proliferations with histopathologic features of "eccrine" poroma could be of apocrine origin.

Verrucous cysts: histopathologic characterization and molecular detection of human papillomavirus-specific DNA

Verrucous cyst is an uncommon newly described benign epithelial cyst which may be associated with human papillomavirus infection. The purpose of this project was to study the clinicopathological features of verrucous cysts and to demonstrate human papillomavirus (HPV) by polymerase chain reaction (PCR) in these lesions. We have analyzed 5 examples of verrucous cysts: the age range of the patients was between 37-82 years and the most common locations were face and extremities. Clinically the lesions were interpreted as cyst (2), dermatofibroma (2) and basal-cell carcinoma (1). Histopathologic examination of the biopsy specimens showed in all cases an intradermal infundibular cyst lined by a papillated and/or digitated epithelium with focal prominent hypergranulosis and irregular keratohyalin granules. Furthermore, numerous whorls of keratinocytes (so-called squamous eddies) were present within the squamous areas of the hyperplastic epithelium of the cyst, morphologically reminiscent of inverted follicular keratosis. Architectural and cytological features of malignancy were not present. Sections of paraffin-embedded tissue of the 5 verrucous cysts and of 5 "conventional" follicular cysts, infundibular type, were investigated for the presence of HPV DNA sequences by PCR using consensus primers. In all 5 cases of verrucous cysts, HPV-specific DNA sequences were detected, whereas all follicular cysts, infundibular type, were negative. These results support the concept that verrucous cysts can be added to the large spectrum of HPV-induced cutaneous neoplasms. Further studies are needed to identify the specified HPV-type in these distinctive benign cystic proliferations.

Multiple infundibular tumours of the head and neck

A condition of multiple benign and sometimes self-healing infundibular tumours of the skin is described. It effects the sun-exposed areas of the head and neck in Caucasians. The individual lesions consist of a cluster of thick pockets, representing in many details the supra-sebaceous portions of the follicular unit. Follicular poroma, tumours of the deeper part of the follicular infundibulum, virus warts, inverted follicular keratosis and prurigo nodules do not correspond adequately with the appearance described in the present series of six cases.

Infundibular keratosis--a prototype of benign infundibular tumours

Three cases of a benign follicular tumour of infundibular origin are reported. The neoplasms were solitary, verrucous, slowly-growing papules or nodules on the face, which were diagnosed clinically as verruca vulgaris or seborrhoeic keratoses. Histologically, several epithelial lobules were seen, mainly above the level of the surface of the surrounding skin, with characteristic funnel-shaped invaginations. The tumours occasionally contained vellus hairs or were connected with sebaceous glands and/or hair follicles at their bases, indicating their follicular origin. The tumour masses consisted of peripherally arranged basaloid and inner squamoid cells. The latter cells contained more glycogen and appeared paler with haematoxylin and eosin (H&E) stains than the normal inter-follicular squamous cells. Neither clear cells nor squamous eddies were observed. Palisading of the basaloid cells was not a prominent feature. The name 'infundibular keratosis' is proposed for such tumours, which probably represent the prototype of infundibular tumours of the hair follicle.