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

Bulboma: A Benign Keratosis With Differentiation Toward the Lower Segment of the Hair Follicle

ABSTRACT

Bulboma is an appellation proposed to designate a distinctive solitary keratosis exhibiting differentiation toward the bulb of the lower segment of the hair follicle. Bulboma is composed of a papillated proliferation of epithelial cells beneath which is a broad front of interconnected follicular papillae. Overlying these coalescing follicular papillae are follicular germinative cells ascending into matrical cells and supramatrical cells. Cells demonstrating differentiation toward Huxley's and Henle's layer of the inner root sheath at the level of the bulb are present including strikingly bright eosinophilic trichohyalin granules and the blue-grey corneocytes of the stem. There is overlying hypergranulosis and orthokeratosis. The clinical and histopathological findings in 4 cases of bulboma, a rare, benign solitary keratosis are presented.

Panfolliculoma with an endophytic architecture resembling a hair follicle: a report of three cases

Panfolliculoma is a benign follicular tumor comprised of all components of the hair follicle. We report three cases of panfolliculoma with a solid, endophytic architecture, which at scanning magnification had the profile of a hair follicle. The epithelial components included uniform dark blue germinative cells, matrical cells, clear cells and cells containing trichohyaline granules. All the cases also had a central hyperkeratotic horn resembling a hair shaft. Two patients were female and one was male. Two lesions were located on the head and neck, and one was located on the leg. Clinical differential diagnoses included basal cell carcinoma, foreign body and cyst.

Panfolliculoma and histopathologic variants: a study of 19 cases

Panfolliculoma (PF) is an uncommon benign follicular neoplasm exhibiting differentiation toward all components of a hair follicle. Several pathologic manifestations have been described in a limited number of cases. We studied 19 cases of PF to summarize the clinical parameters and to classify this unique neoplasm histopathologically. A study of the largest sample series of PF has been performed here. The lesions affect both genders after age 20. The head is the most common site of PF of all types. On microscopic examination, all cases demonstrated advanced follicular differentiation by showing cell components of infundibulum, isthmus, stem, bulb, and mesenchymal papilla. Based on the findings and various patterns in histopathology, we classified PF into 3 subtypes: nodular, superficial, and cystic. The superficial and cystic variants account for most of the cases in our study. The histopathologic differential diagnosis is also discussed for each subtype.

Epidermal panfolliculoma: an adnexal proliferation with advanced follicular differentiation confined to the epidermis

Follicular differentiation can be exhibited by a variety of epidermal lesions. We report an example of panfolliculoma purely confined to the epidermis. The lesion presented as a verrucous plaque on the leg of a 55-year-old man. Histopathologic sections showed an acanthoma with follicular differentiation including areas mimicking the follicular germ, matrix, root sheath and infundibular components.

Epidermal panfolliculoma: A report of 2 cases

There are a variety of known lesions displaying differentiation toward various portions of the hair follicle. However, there is no established term given to an intraepidermal entity showing differentiation toward both upper and lower portions of the follicle. We report 2 cases of a histologically distinct variant of panfolliculoma that, unlike the traditionally described panfolliculoma, is located intraepidermally. The lesions were taken from the medial thigh of an 81-year-old man and the lateral thigh of a 61-year-old woman, clinically suspected to be an inflamed seborrheic keratosis and a squamous cell carcinoma, respectively. Each case appeared as a demarcated plaque-like lesion with mild epidermal hyperplasia and prominent differentiation toward the upper and lower segments of the hair follicle. The specific histologic features included focal differentiation toward the infundibulum and isthmus (infundibular cystic structures and pilar epithelium), inner root sheath (trichohyalin granules), the matrix/hair shaft (matrical cells, ghost cells and refractile keratinization), and follicular germ/papilla (papillary mesenchymal bodies). This varied histology is similar to that of the previously described panfolliculoma, differing in that it emanates largely from the epidermis rather than being predominantly dermally located. We propose the term "epidermal panfolliculoma" for these lesions.