Inverted follicular keratosis

Seborrheic Keratosis or Squamous Carcinoma? Clinical Examination versus Biopsy: The Importance of Criticism

We compare the results of clinical observation and histopathology analysis for developing a differential diagnosis of seborrheic keratosis (SK) of the external auditory canal (EAC). A 46-year-old man with a history of a recurrent lesion in the EAC underwent clinical observation of the skin lesion's appearance, computed tomography (CT) scan, magnetic resonance imaging (MRI), and several biopsies. Initially, a benign form of SK was diagnosed based on several biopsies performed over a 10-year period. The lesion's appearance was consistent with a malignant disease, which led the clinician to perform a CT scan and an MRI scan. The patient underwent partial petrosectomy to completely remove the lesion as CT and MRI scans showed an infiltrative process. Squamous carcinoma was the final histological diagnosis. The patient was disease free at 1 year of follow-up after petrosectomy. In conclusion, if there are inconsistencies between clinical observation and histological report, additional tests should be performed to exclude the malignity of a lesion.

CD34 and BerEP4 Are Helpful to Distinguish Basaloid Tricholemmoma From Basal Cell Carcinoma

Tricholemmoma, a benign follicular neoplasm with outer root sheath differentiation, typically comprises clear or pale cells, and when multiple is pathognomic of Cowden's syndrome. The tumor is probably underrecognized and in basaloid examples can be difficult to distinguish from basal cell carcinoma (BCC). We studied 55 tricholemmomas (including 15 basaloid cases) and compared immunohistochemical profile with nodular BCC from our archives. Basaloid and non-basaloid tricholemmomas had similar staining characteristics. BerEP4 was focally positive (range 10%-20%) in only 3/39 (7.7%) tricholemmomas compared with widespread positivity in BCC (90.8%, 139 of 151 cases with ≥50% tumor area stained). CD34 was expressed, usually focally (median 20%, range 10%-90%), in 52/53 (98.1%) tricholemmomas and was negative in all 21 BCCs stained. EMA staining lacked sensitivity or specificity in differentiating tricholemmoma from BCC. Five or more Merkel cells were found in 7/17 (40.1%) tricholemmomas and 1/23 (4.3%) nodular BCCs studied. In summary, immunohistochemistry is helpful in distinction between tricholemmoma, including difficult basaloid examples (BerEP4 negative or focal, CD34 positive) compared with BCC (BerEP4 widespread in most cases, CD34 negative). The presence of 5 or more Merkel cells is a relatively specific but not a particularly sensitive discriminator.

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.

Pigmented tumor in the nostril

A 64-year-old man was noted to have a single pigmented lesion in the nostril of his nose. Clinical examination revealed a 5 mm nodular growth and brown lesion. With a presumed clinical diagnosis of malignant skin tumor, a biopsy was performed. The histological examination revealed the unexpected diagnosis of pigmented inverted follicular keratosis.

The inverted follicular keratosis is an uncommon benign lesion that is usually diagnosed histologically rather than clinically. It commonly simulates other proliferative skin lesions.

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.

Multiple inverted follicular keratoses as a presenting sign of Cowden's syndrome: case report with human papillomavirus studies

Inverted follicular keratosis is characterized by a squamous epithelial expansion of the infundibular portion of the hair follicle in an exophytic and endophytic pattern. The lesion is often associated with squamous eddies similar to an irritated keratosis and may have a superficial papillomatous architecture. The lesion most often arises as a solitary nodule on the face of middle age to elderly individuals. Inverted follicular keratosis has been described as a distinct entity by some while others believe that it is related to trichilemmomas and/or verruca vulgares. The cutaneous pathology of Cowden's syndrome is characterized by multiple trichilemmomas. We present a woman who fulfills the clinical criteria for Cowden's syndrome and who initially presented with multiple inverted follicular keratoses. Also, in situ hybridization studies performed on the patient's keratoses do not reveal evidence of human papillomavirus infection.

Inverted follicular keratosis

Inverted follicular keratosis, a benign tumor of the skin believed to arise from the infundibular portion of the hair follicle that can involve perioral skin, has a unique histologic picture. It can be confused with forms of skin cancer; with knowledge of this entity, oral and maxillofacial surgeons may be able to avoid unnecessary surgery. The clinical and microscopic findings of 12 cases of inverted follicular keratosis are reported.

Inverted follicular keratosis of the lip

Nine cases of inverted follicular keratosis (IFK) of the lips are reported. Eight of these occurred on the lower lip, a previously unreported location. The clinical and histologic features of IFK are discussed. The possibility of confusing this lesion with squamous cell carcinoma is emphasized, and the histologic criteria for differentiation are enumerated.

Adnexal participation in formation of cutaneous tumors following topical application of 9,10-dimethyl-benzanthracene

The response of the hair follicle apparatus to topical 9, 10-dimethyl-benzanthracene applications was studied in several strains of mice and rats. Early follicular destruction in mice was associated with subsequent formation of large number of epithelial tumors. Preserved follicular structures in rats proliferated with the formation of low incidence of adenomas and trichoepitheliomas. Hair nevi, hairfollicle nevi and trichofolliculomas, unrelated to treatment, were observed in several animal strains.

Inverted follicular keratosis

We reviewed 17 cases of inverted follicular keratosis. The median age of the patients at the time of surgery was 69 years. Follow-up in 14 cases showed no recurrences of inverted follicular keratosis, which is a benign skin lesion, often mistaken clinically and pathologically for a malignancy. Inverted follicular keratosis is characterized histologically by the presence of squamous eddies, acantholysis, acanthosis, and hyperkeratosis.