Folliculosebaceous neoplasms: A review of clinical and histological features

ABERRANT WNT SIGNALING INDUCES COMEDO-LIKE CHANGES IN THE MURINE UPPER HAIR FOLLICLE

Stem cell proliferation and differentiation must be carefully balanced to support tissue maintenance and growth. Defective stem cell regulation may underpin diseases in many organs, including the skin. Lrig1-expressing stem cells residing in the HF junction zone (JZ) support sebaceous gland (SG) homeostasis. An emerging hypothesis from observations in both mouse and human holds that imbalances in key stem cell regulatory pathways such as Wnt signaling may lead to abnormal fate determination of these Lrig1^+ve cells. They accumulate and form cystic structures in the JZ that are similar to the comedones found in human acne. To test the possible involvement of Wnt signals in this scenario, we used the Lrig1-CreERT2 mouse line to modulate Wnt signaling in JZ stem cells. We observed that persistent activation of Wnt signaling leads to JZ cyst formation with associated SG atrophy. The cysts strongly express stem cell markers and can be partially reduced by all-trans retinoic acid treatment as well as by Hedgehog signaling inhibition. Conversely, loss of Wnt signaling leads to enlargement of JZ, infundibulum and SGs. These data implicate abnormal Wnt signaling in the generation of mouse pathologies that resemble human acne and respond to acne treatments.

Desmoplastic Trichoepithelioma With Pseudocarcinomatous Hyperplasia: A Folliculosebaceous Neoplasm in Young Persons

ABSTRACT

Pseudocarcinomatous desmoplastic trichoepithelioma (PDTE) features verrucous squamous epidermal hyperplasia with a jagged undersurface overlying cords of follicular germinative cells in a fibrotic stroma. To date, only 5 cases have been reported. We identified 7 new PDTEs from 2 institutions and reviewed their clinical manifestations and immunohistochemical profile. The median age was 14 years (range 8-34 years). New findings included vacuolization of the basal layer of the pseudocarcinomatous surface epithelium, and the frequent presence of singly distributed sebocytes within the cords of basaloid cells. The immunohistochemical profile resembles desmoplastic trichoepithelioma, with expression of TDAG51, CK15, and Ber-Ep4. Colonizing CK20+ Merkel cells were present in all cases. PDTE needs to be differentiated from malignant neoplasms such as squamous cell carcinoma, morphoeic basal cell carcinoma, and microcystic adnexal carcinoma. Recognizing the features of this sclerosing folliculosebaceous neoplasm facilitates accurate diagnosis and avoids overtreatment.

A case of Giant Perifollicular Fibroma - a Diagnostic Challenge

Perifollicular fibroma (PFF) is a rare proliferative lesion originating from the perifollicular connective tissue sheath. It may be congenital or acquired manifesting as skin colored to pink, asymptomatic papules of 1-5 mm in size. They are commonly distributed in the head and neck region. Multiple PFFs may be associated with internal malignancy or as a part of Birt-Hogg-Dube syndrome. Histopathology serves as an essential tool in clinching the diagnosis. Herein we report a case of giant congenital PFF.

Are clinicians successful in diagnosing cutaneous adnexal tumors? a retrospective, clinicopathological study

Background/aim

Cutaneous adnexal tumors (CAT) are rare tumors originating from the adnexal epithelial parts of the skin. Due to its clinical and histopathological characteristics comparable with other diseases, clinicians and pathologists experience difficulties in its diagnosis.We aimed to reveal the clinical and histopathological characteristics of the retrospectively screened cases and to compare the prediagnoses and histopathological diagnoses of clinicians.

Materials and methods

The data of the last 5 years were scanned and patients with histopathological diagnosis of CAT were included in the study.

Results

A total of 65 patients, including 39 female and 26 male patients aged between 8 and 88, were included in the study. The female to male ratio was 1.5, and the mean age of the patients was 46.15 ± 21.8 years. The benign tumor rate was 95.4%, whereas the malignant tumor rate was 4.6%. 38.5% of the tumors were presenting sebaceous, 35.4% of them were presenting follicular, and 18.5% of them were presenting eccrine differentiation. It was most commonly seen in the head-neck region with a rate of 66.1%. When clinical and histopathological prediagnoses were compared, prediagnoses and histopathological diagnoses were compatible in 45% of the cases. Most frequently, it was the basal cell carcinoma, epidermal cyst, and sebaceous hyperplasia identified in preliminary diagnoses.

Conclusion

Cutaneous adnexal tumors are very important, as they can accompany different syndromes and may be malignant. Due to difficulties in its clinical diagnosis, histopathological examination must be performed from suspicious lesions for definitive diagnosis.

Homeobox transcriptional factor engrailed homeobox 1 is expressed specifically in normal and neoplastic sweat gland cells

AIMS

A number of homeobox transcriptional factors are utilised as organ-specific markers in the histopathological diagnosis of neoplasms. We have screened a homeobox gene that is expressed specifically in normal sweat gland cells and is useful for the histopathological diagnosis of sweat gland neoplasms.

METHODS AND RESULTS

By screening an open database resource of The Human Protein Atlas, 37 genes among the 235 homeobox transcriptional factors were found to be expressed specifically in the skin. Among those 37 genes, the engrailed homeobox 1 (En1) was expressed in normal eccrine glands but not in the epidermal keratinocytes. Expression of En1 was found throughout the eccrine glands, but not in the apocrine secretory coils, sebaceous glands or hair follicles. Expression of En1 was examined immunohistochemically in 111 cases of cutaneous epithelial neoplasms. All nine cases of poroma, seven cases of spiradenoma and six cases of syringoma, which are considered to differentiate towards eccrine glands, showed positive nuclear staining in most of the tumour cells. Sebaceous gland and hair follicle tumours were immunonegative. En1 was expressed focally in the epidermal neoplasms of seborrheic keratosis and squamous cell carcinoma.

CONCLUSION

Engrailed homeobox 1 was expressed specifically in normal eccrine glands and was expressed in most of the tumour cells of sweat gland neoplasms with eccrine gland differentiation. En1 was expressed focally in epidermal neoplasms; however, it was absent in sebaceous or hair follicle neoplasms. These findings will help in the histopathological diagnosis as well as understanding of the histogenesis of sweat gland neoplasms.