Skin nonmelanocytic tumor
Benign (nonmelanotic) epidermal tumors or tumor-like lesions
Inverted follicular keratosis
Topic Completed: 1 September 2017
Minor changes: 4 November 2020
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Inverted follicular keratosis [title]
Table of Contents
Definition / general | Essential features | Terminology | Epidemiology | Sites | Etiology | Case reports | Treatment | Clinical images | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Differential diagnosis | Additional references | Board review style question #1 | Board review style answer #1Cite this page: Dunn ALJ, Shalin SC. Inverted follicular keratosis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumornonmelanocyticinvertedfollicularkeratosis.html. Accessed January 22nd, 2021.
Definition / general
- Found on the head and neck
- Usually affects older males
Essential features
- Benign, usually endophytic proliferation of follicular infundibulum with squamous eddies
Terminology
- IFK
Epidemiology
- Older men
Sites
- Predominantly head and neck
Etiology
- May be irritated seborrheic keratosis, irritated verruca vulgaris or keratotic lesion that involves the infundibular region of hair follicle
Case reports
- 24 year old woman with vulvar lesion (Int J Gynecol Pathol 2000;19:369)
- 55 year old woman with keratotic lesion of the lip (Pan Afr Med J 2014;18:304)
Treatment
- Not necessary; biopsy is usually curative
Clinical images
Images hosted on other servers:
8 - 12 mm pedunculated nodule
Gross description
- Solitary skin colored papule with or without filiform growth measuring less than 1 cm
Microscopic (histologic) description
- Patterns include:
- Wart-like variant
- Keratoacanthoma-like pattern
- Solid nodular
- Well circumscribed endophytic growth of squamous cells with lobular extension into the dermis; exophytic lesions with a keratoacanthoma-like appearance have been described
- Variable number of squamous eddies; may be increased secondary to irritation
- Peripheral basaloid cells with occasional mitotic activfty
Microscopic (histologic) images
Contributed by Andrew L.J. Dunn, M.D.
Various magnifications
Wart-like variant
Positive stains
- BCL2: upregulated in dendritic cells compared to seborrheic keratosis (J Cutan Pathol 2006;33:498)
Differential diagnosis
Additional references
Board review style question #1
Which of the following is true about inverted follicular keratosis?
- BCL2 is downregulated in dendritic cells
- Squamous eddies are an atypical finding in inverted follicular keratosis
- These lesions are more commonly found on the head and neck
- These lesions are more common in young women
Board review style answer #1
C. These lesions are more commonly found on the head and neck
BCL2 has been found to be upregulated in the dendritic cells of IFKs but not seborrhea keratosis. IFKs are typically found on the head and neck of older males. Squamous eddies are a usual finding in IFKs.
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BCL2 has been found to be upregulated in the dendritic cells of IFKs but not seborrhea keratosis. IFKs are typically found on the head and neck of older males. Squamous eddies are a usual finding in IFKs.
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