A revaluation of trichofolliculoma: the histopathological and immunohistochemical features

Very High Frequency Ultrasonographic Features of Trichofolliculoma: An Observational Study

Background

Trichofolliculoma (TF) is a rare condition, and its imaging features have been inadequately studied, leading to frequent misdiagnoses in clinical practice.

Objective

The aim of our study was to investigate the very high frequency (VHF) ultrasound characteristics of TF, identify features that could assist in the differential diagnosis of TF versus other benign and malignant lesions.

Methods

We collected clinical data from 24 patients with histologically confirmed TF between February 2019 and June 2024. We retrospectively analyzed the VHF ultrasound image characteristics of the lesions, including their location, skin layers involved, size, shape, margin, boundary, internal echo characteristics, and blood flow patterns.

Results

The VHF ultrasound image features of the 24 TF cases showed that the lesions were located in the epidermis, dermis, and subcutaneous tissue in 8 cases, in the dermis and subcutaneous tissue in 2 cases, and in the deep dermis and subcutaneous tissue in 14 cases. The maximum diameter was approximately 23.3×8.7 mm. The lesions were mostly regular in shape (75%), with predominantly inhomogeneous low echo (95.8%). Most lesions contained cystic echoes (70.8%), some had short linear strong echoes within (66.6%), and partial posterior echo enhancement was observed in some lesions (41.6%). Half (50%) of the lesions showed peripheral blood flow signals. The consistency analysis of the VHF ultrasound image features showed Kappa values greater than 0.7, indicating good agreement.

Conclusion

The VHF ultrasound images of TF exhibit characteristic features. Specifically, the identification of the lesion's location, the involved skin layers, internal echo features, and blood flow patterns offers novel insights that enhance diagnostic accuracy and possesses significant auxiliary value in clinical diagnosis and treatment. This study contributes unique findings to the existing literature, further elucidating the VHF ultrasound characteristics of TF and underscoring its potential in improving clinical practice.

Trichofolliculoma - A Case Report

ABSTRACT

Trichofolliculoma is a rare benign, hamartomatous adnexal tumour of the skin. Aetiology seems to be unclear. It is usually seen in adults, with no gender predilection. The most commonly involved sites are the face and scalp. It appears as a papule or nodule with small protruding hairs, which is a classic feature of the tumour. It has unique diagnostic and histopathological features that help in making a definitive diagnosis. Here, we report an exemplary case of an adult male patient aged 45 years with a gradual progressive diffuse swelling on the left side of the face for 1.5 years. Clinically, it was diagnosed as a sebaceous cyst, but after the biopsy histopathological evaluation was performed, and the diagnosis was confirmed as trichofolliculoma.

Trichofolliculoma of the external auditory canal: a case report and review of the literature

Trichofolliculoma is a rare tumor that arises from immature hair follicular tissue. In this report, we present the case of a 51-year-old man with a trichofolliculoma in the left external auditory canal. Uniquely, there was no prior trauma in this patient, despite previous trauma being hypothesized in the etiology of this tumor. The lesion was excised using microsurgical instruments and the tumor was closely adherent to the cartilage of the external auditory canal. Histopathology following excisional biopsy confirmed the diagnosis.

Bowen disease with matrical differentiation: Report of an exceptional histopathologic presentation

Matrical differentiation is the distinctive feature of pilomatricoma and other purely matrical adnexal neoplasms; additionally, foci of matrical differentiation have been also described in hybrid cysts of Gardner syndrome, as well as in a wide variety of benign and malignant cutaneous tumors, including basal cell carcinoma. We report an exceptional case of Bowen disease exhibiting multiple foci of matrical differentiation, as confirmed by means of immunohistochemical studies. Several types of divergent, non-squamous differentiation have been exceptionally reported in cutaneous squamous cell carcinoma in situ (cSCCIS), including sebaceous, mucinous/glandular, poroid, tricholemmal, and neuroendocrine differentiation; matrical differentiation may be added to this list. Our findings further emphasize the undifferentiated nature of neoplastic cells in cSCCIS.

Hair Follicle Nevus Located on the Neck: Comparison with Accessory Tragus, Cervical Chondrocutaneous Branchial Remnants and Trichofolliculoma

Hair follicle nevus (HFN) is a rare, benign, follicular hamartoma that most frequently presents as a congenital nodule on the face. We experienced a rare case of HFN on the neck of a 14-year-old boy and performed a pilot immunohistochemical study with cytokeratin 19 (CK19) to compare the staining pattern of hair follicles in HFN and its differential diagnoses, accessory tragus, cervical chondrocutaneous branchial remnants (CCBR) and trichofolliculoma. With hematoxylin and eosin stain, HFN showed numerous tiny hair follicles in the dermis with several sebaceous and eccrine glands, and perifollicular fibrous thickening. With CK19 stain, some hair follicles in HFN and CCBR showed positive expression, a few hair follicles in accessory tragus showed weak expression, and no hair follicles in trichofolliculoma showed expression. The present report supports the view that HFN, accessory tragus and CCBR are within the same spectrum of hamartomas.

Chronological changes in trichofolliculoma: Folliculosebaceous cystic hamartoma is not a very-late-stage trichofolliculoma

Some authors have reported that the secondary hair follicles in trichofolliculomas (TF) undergo regressive changes and are subsequently replaced by the developed sebaceous elements, and that folliculosebaceous cystic hamartoma (FSCH) is a TF at a very late stage. In the present study, we revaluated the histopathological features of 40 TF lesions, focusing on their chronological changes. The results of the present study indicate that while the secondary follicles in the TF exhibited the hair cycle, the normal hair cycle was out of control, and tertiary hair follicles randomly developed from the involuting secondary follicles. The repeated development of hair follicles in this disordered hair cycle caused the development of chains of several continuous hair follicles in late-stage TF. In the TF lesions, no features indicating the replacement of the regressing secondary hair follicles by any sebaceous elements were observed, thereby suggesting that FSCH is not a very-late-stage TF.

Folliculosebaceous neoplasms: A review of clinical and histological features

Numerous benign and occasionally malignant tumors arise from the folliculosebaceous apparatus. Confusing terminology, rarity of malignant variants and overlapping histological features can lead to diagnostic uncertainty. This review highlights the clinical and histopathological features that help to classify these entities, as well as the various syndromes associated with certain members of this large family of tumors.

Benign follicular tumors

Benign follicular tumors comprise a large and heterogeneous group of neoplasms that share a common histogenesis and display morphological features resembling one or several portions of the normal hair follicle, or recapitulate part of its embryological development. Most cases present it as clinically nondescript single lesions and essentially of dermatological relevance. Occasionally, however, these lesions be multiple and represent a cutaneous marker of complex syndromes associated with an increased risk of visceral neoplasms. In this article, the authors present the microscopic structure of the normal hair follicle as a basis to understand the type and level of differentiation of the various follicular tumors. The main clinicopathological features and differential diagnosis of benign follicular tumors are then discussed, including dilated pore of Winer, pilar sheath acanthoma, trichoadenoma, trichilemmoma, infundibuloma, proliferating trichilemmal cyst/tumor, trichoblastoma and its variants, pilomatricoma, trichodiscoma/fibrofolliculoma, neurofollicular hamartoma and trichofolliculoma. In addition, the main syndromes presenting with multiple follicular tumors are also discussed, namely Cowden, Birt-Hogg-Dubé, Rombo and Bazex-Dupré-Christol syndromes, as well as multiple tumors of follicular infundibulum (infundibulomatosis) and multiple trichoepitheliomas. Although the diagnosis of follicular tumors relies on histological examination, we highlight the importance of their knowledge for the clinician, especially when in presence of patients with multiple lesions that may be the cutaneous marker of a cancer-prone syndrome. The dermatologist is therefore in a privileged position to recognize these lesions, which is extremely important to provide further propedeutic, appropriate referral and genetic counseling for these patients.

Trichofolliculoma presenting as lobulated mass: a rare presentation

Trichofolliculoma represents abortive differentiation of pluripotent skin cells toward hair follicles. We present a case of an adult female with lobulated mass involving the tip and dorsum of the nose for the last 15 years. The systemic and radiological examinations were noncontributory. The clinical diagnosis was thought to be dermoid cyst. The fine-needle aspiration cytology of the lobulated mass was performed, and the cytology smears showed anucleate squames admixed with sebaceous cells. The possibility of a benign skin adnexal lesion was suggested. The biopsy was done, and the final diagnosis of trichofolliculoma was made. The wide local excision of the mass was performed, and no recurrence was noted during the follow-up of 1 year.

The changes in the expression levels of follicular markers in keratoacanthoma depend on the stage: keratoacanthoma is a follicular neoplasm exhibiting infundibular/isthmic differentiation without expression of CK15

BACKGROUND

Although the precise etiology of keratoacanthoma (KA) is unknown, KA is generally assumed to differentiate toward hair follicles based on previous studies of experimental carcinogenesis.

METHODS

We performed a comprehensive immunohistochemical study of various follicular markers in all stages of KA. A total of 67 tumors, including 16 early or proliferative stage lesions, 43 well-developed stage lesions, five regressing stage lesions and three regressed stage lesions, were subjected to the analysis.

RESULTS

CK15 (clone C8/144B), CK19 and CD34 were not expressed at any stage. CK1, CK10, CK16, CK17, CK15 (clone LHK15) and calretinin showed dynamic changes in their expression in KA depending on the stage.

CONCLUSIONS

KA is a follicular neoplasm with infundibular/isthmic (upper segmental region of hair follicles) differentiation. It is considered that early or proliferative stage tumors show keratin-filled invaginations with infundibular differentiation and gradual isthmic differentiation. Well-developed examples of KA generally show isthmic differentiation in the whole lesions. The regressed stage KAs lose the features of this type of follicular differentiation and show epidermal characteristics. No expression of CK15 (clone C8/144B) was observed in KAs, although this finding is insufficient to completely rule out the correlation between the regression of KA and the hair follicle cycle.

Vulvar Adnexal Lesions: A 32-Year, Single-Institution Review From Massachusetts General Hospital

Context.—Because the skin and modified mucosal surfaces of the vulvar region contain dense apocrine glands and anogenital mammary-like glands, in addition to eccrine glands and folliculosebaceous units, benign as well as malignant lesions derived from these adnexal structures are, not surprisingly, found in the vulva. However, their incidence occurring in the vulva has not been reported, to our knowledge.

Objective.—To determine the incidence of various vulvar adnexal lesions.

Design.—We performed a retrospective review (1978–2010) of the cases at our institution.

Results.—A total of 189 vulvar adnexal lesions were identified. Most of these lesions were benign (133 of 189; 70%), with hidradenoma papilliferum being the most common, followed by syringoma and various types of cysts. Rare cases of tubular adenoma, poroma, spiradenoma, hidradenoma, cylindroma, sebaceoma, and trichoepithelioma were identified. Malignant adnexal neoplasms comprised the remaining 30% (56 of 189) of the cases. Extramammary Paget disease was the most common (49 of 56), and 29% (14 of 49) demonstrated an invasive component. Rare cases of basal cell carcinoma, sebaceous carcinoma, apocrine carcinoma, adenoid cystic carcinoma, and spiradenocarcinoma were identified.

Conclusions.—In this retrospective review, we identified several benign entities that have not been previously reported on the vulva, namely pilomatricoma, poroma, spiradenoma, and sebaceoma. Hidradenoma papilliferum and extramammary Paget disease were the most common benign and malignant adnexal neoplasms, respectively. The spectrum of various vulvar adnexal lesions appears to reflect the frequency of the underlying glandular elements.

Tricholemmoma and clear cell squamous cell carcinoma (associated with Bowen's disease): immunohistochemical profile in comparison to normal hair follicles

There have been only a few reported comparative immunohistochemical studies of normal hair follicles and tricholemmomas. Clear cell squamous cell carcinomas (SCCs), which are derived from Bowen's disease, histopathologically mimic or are difficult to distinguish from tricholemmal carcinoma. The purpose of and methods used in the present study are as follows: (1) evaluation of whether the immunohistochemical profile (cytokeratin (CK)1, CK10, CK17, CD34, and D2-40) in normal hair follicles is retained in tricholemmomas (11 lesions); and (2) a study of the immunohistochemical profile of in situ or superficially invasive clear cell SCCs (associated with Bowen's disease) (10 lesions) to investigate the presence or absence of tricholemmal differentiation markers in these lesions. The present study demonstrated that (1) the immunohistochemical profile of the normal outer root sheath cells was generally retained in tricholemmomas; (2) in contrast to the D2-40 expression in tricholemmomas (only a peripheral pattern, which is similar to that in the normal outer root sheath), the CD34 expression in tricholemmomas represented in a diffuse pattern, a peripheral pattern, and a combined diffuse and peripheral pattern; (3) tricholemmomas are benign neoplasms with outer root sheath (below the isthmus) differentiation, which characteristically show upregulation of CD34 expression with some functionally similar conditions to the terminal hair follicles in the anagen phase; and (4) there is no clear immunohistochemical evidence of tricholemmal differentiation in clear cell SCC (associated with Bowen's disease).