Desmoplastic trichoepithelioma: report of a case illustrating its natural history

First described more than 30 years ago, desmoplastic trichoepithelioma is a rare but benign adnexal neoplasm. Most often identified in middle-aged individuals and females, desmoplastic trichoepithelioma usually is a solitary annular plaque. Though the tumors are benign, the possibility of malignant neoplasm may spark both clinical and histologic concern. A full-thickness skin biopsy is advisable when desmoplastic trichoepithelioma is suspected. A patient's clinical history may provide some clues to help guide diagnosis, as the tumors may be present for years and slow growth is commonly reported. We present a patient with desmoplastic trichoepithelioma that uniquely documents and supports the typical natural history of this tumor, as demonstrated by annual school photographs.     

Desmoplastic trichoepithelioma nosology. Reappraisal about a case developed on a varicella scar

We report the case of a 51-year-old woman who presented with a progressive elevation of the border of an old varicella scar. The lesion which was clinically diagnosed as a basal cell carcinoma turned out to be a typical desmoplastic trichoepithelioma. The development of desmoplastic trichoepithelioma in an area of scarring has not been previously reported. The nosology of this tumor is discussed with particular emphasis on its possible relationship to morphoeic basal cell carcinoma, thus questioning it as a true tumor sui generis.     

Two cases of desmoplastic trichoepithelioma

Desmoplastic trichoepithelioma is a rare tumor that usually exhibits the distinct clinical features of a solitary granuloma annulare-like growth on the face. We experienced two cases of desmoplastic trichoepithelioma, one of which showed unusual clinical features and the other of which was a typical case. The first case was a 20-year-old female who presented with a five year history of a solitary yellowish nodule, 5 mm in diameter, centrally between the eyebrows. There was no central dimple or elevated border. The other case was a 40-year-old female who presented with a ten year history of a solitary nodule, 6 mm in diameter on her left cheek. The latter lesion had a typical depressed area in the center of the nodule with elevated borders and could be clinically diagnosed as desmoplastic trichoepithelioma. The histopathological examination revealed that both of them were desmoplastic trichoepithelioma. Histopathological comparison of the two specimens suggested that the clinical dimple in the center of the first tumor might be the result of stromal dystrophic changes induced by the tumor.     

Desmoplastic trichoepithelioma with perineural involvement: a series of seven cases

Desmoplastic trichoepithelioma (DTE) is a benign follicular tumor occurring most commonly within facial skin of young and middle-aged women, morphologically characterized by a superficial dermal proliferation of basaloid cells growing in narrow strands embedded in a desmoplastic stroma associated with small keratinizing cysts. DTE must be distinguished from other benign epithelial proliferations such as syringoma, microcystic adnexal carcinoma and infiltrating basal cell carcinoma. Among morphological features useful in that distinction, perineural involvement is considered a feature indicative of malignancy. We present a series of seven DTEs with otherwise typical presentation and morphology, nevertheless showing epithelium present in the perineural spaces of adjacent small dermal nerves. Patients ranged in age from 14 to 66 years (mean 44 years). All seven tumors were restricted to dermis, showed strands of basaloid epithelium in desmoplastic stroma and contained CK20-positive cells. Additionally, five of five examined tumors displayed diffuse expression of p75 neurotrophin receptor. Five patients were followed up clinically (follow-up time range: 2 months-4 years). No tumor recurrence was observed in any of these patients. We postulate that perineural involvement is an unusual feature of DTE that should not be equated with malignancy or lead to unnecessary over-treatment.     

Merkel cells are integral constituents of Desmoplastic trichoepithelioma: an immunohistochemical and electron microscopic study

The incidence of Merkel cells has previously been investigated in a number of inflammatory and tumorous lesions of the skin. Special attention was given to tumors with follicular differentiation. In the present study we examined the localization of Merkel cells in another adnexal tumor, the desmoplastic trichoepithelioma (n= 15), as well as in its main differential diagnosis, the morpheiform basal-cell carcinoma (n=30). Using immunohistochemical methods, we found Merkel cells as a stable constituent in desmoplastic trichoepitheliomas, but failed to detect them in morpheiform basal-cell carcinomas. These findings might therefore be an important tool in the sometimes very difficult but clinically imperative distinction between these two conditions. Furthermore, our study may be of interest in the discussion about the origin of desmoplastic trichoepitheliomas. High numbers of Merkel cells in desmoplastic trichoepitheliomas indicate a bulge-derived origin of this adnexal tumor, since high numbers of Merkel cells, especially in the bulge, were recently discovered. Although the significance of Merkel cell hyperplasia in desmoplastic trichoepithelioma is not presently understood, a regulatory role of the Merkel cell in growth and development of this adnexal tumor is suggested.     

Imiquimod as an Adjuvant Treatment Measure for Desmoplastic Trichoepithelioma

Desmoplastic trichoepithelioma is a rare benign adnexal tumor. Although it is a benign lesion, patients often want to treat it due to cosmetic concerns when it occurs in an easily visible site. For our two cases, topical 5% imiquimod was an attractive treatment option as it is applied by the patients themselves and it has minimal side effects, including leaving no scar. However, the lesions recurred after clinical remission. To the best of our knowledge, this is the only report on utilizing imiquimod to treat a benign adnexal tumor, and especially desmoplastic trichoepithelioma.     

A combined case of desmoplastic trichoepithelioma and nevus cell nevus

A 41-year-old woman with desmoplastic trichoepithelioma associated with pigmented nevus presented. Pigmented nevus had been present on her face at birth. She had received cryotherapy and dermabrasion at a small part of the pigmented nevus. As a result of the therapy, the discoloration disappeared. The lesion lately increased and became hard. Histologically, the lesion was composed of two distinctive but intimately mixed cellular components; nevus cells and basaloid cells. In the pigmented lesion, basaloid cells were not present. To our knowledge, this is the first reported case of desmoplastic trichoepithelioma associated with nevocellular nevus in Japan.     

Congenital desmoplastic trichoepithelioma

Desmoplastic trichoepithelioma (DT) is a rare benign adnexal neoplasm considered to have follicular differentiation. It usually presents as an asymptomatic, firm, annular plaque with a raised border. The most common site of occurrence is the face, usually on the cheek. Females are more often affected than males and the age range of patients previously reported is 8-79 years. We present a case of congenital desmoplastic trichoepithelioma. A girl was born at term to a healthy mother after an uneventful pregnancy and was noted to have widespread erythematous plaques with milia-like lesions over the right scalp, face and neck, with some areas of atrophic scarring. Histology and immunohistochemistry of incisional biopsies of the lesions were consistent with a diagnosis of DT. To our knowledge, this is the first reported case of congenital DT.     

Desmoplastic trichoepithelioma and intradermal nevus: a combined malformation

We studied 13 desmoplastic trichoepitheliomas associated with intradermal nevi. Ten intradermal nevi were found among 76 new cases of desmoplastic trichoepithelioma (13%); three additional examples of the combined malformation were seen in consultation. Clinically, desmoplastic trichoepithelioma associated with an intradermal nevus was typically a small, firm or hard, sometimes annular, nodule on the face, particularly the cheek, of a relatively young woman. Microscopically, the combined malformation contained narrow strands of basaloid cells and keratinous cysts in a desmoplastic stroma, intimately mixed with intradermal nests of nevocytes. Melanocytic nevi have been associated with epidermal hyperplasia resembling seborrheic keratoses, follicular cysts, trichostasis spinulosa, syringomas, basal cell carcinomas, and hair follicle formation on the soles. The frequency of the occurrence of intradermal nevus with desmoplastic trichoepithelioma and the close anatomic association of the two elements may indicate that this combined malformation is another example of epithelial induction by melanocytic nevi.     

p75 Neurotrophin receptor differentiates between morphoeic basal cell carcinoma and desmoplastic trichoepithelioma: insights into the histogenesis of adnexal tumours based on embryology and hair follicle biology

Background Tumour development is frequently described in the basic pathology literature as a recapitulation of embryogenesis. However, a link between the embryology of the skin and the histogenesis of adnexal tumours has been largely overlooked. The low‐affinity p75 neurotrophin receptor (p75NTR) has a profound role in hair follicle biology. We therefore speculated that it is involved in the histogenesis of follicular adnexal tumours. One of the most challenging diagnoses in dermatopathology is differentiating morphoeic basal cell carcinoma from desmoplastic trichoepithelioma. Objectives To describe the expression pattern of p75NTR during cutaneous embryogenesis, in the adult hair follicle and in morphoeic basal cell carcinoma and desmoplastic trichoepithelioma. Methods Evaluation of the staining pattern for p75NTR was performed using standard immunohistochemical techniques. For comparison, we examined staining for cytokeratin 20 which highlights Merkel cells. Results All 17 desmoplastic trichoepitheliomas were immunoreactive with > 80% of the cells stained, whereas 12 of the 14 (86%) morphoeic basal cell carcinomas were p75NTR negative. In the two positive cases of morphoeic basal cell carcinoma < 30% of cells were labelled. In the late bulbous hair peg stage and in the postnatal anagen hair follicle p75NTR highlights the outer root sheath. Conclusions Our results support the classification of desmoplastic trichoepithelioma as a follicular hamartoma mimicking the outer root sheath. In contrast, the lack of p75NTR expression in morphoeic basal cell carcinoma favours a concept of this tumour as a more primitive follicular lesion with the characteristics of a carcinoma and not a hamartoma. We suggest including p75NTR as a tool in the differential diagnosis between morphoeic basal cell carcinoma and desmoplastic trichoepithelioma.     

PHLDA1 (TDAG51) is a follicular stem cell marker and differentiates between morphoeic basal cell carcinoma and desmoplastic trichoepithelioma

Background Morphoeic basal cell carcinoma (BCC) and desmoplastic trichoepithelioma can often be difficult to differentiate on routine sections and few reliable immunohistochemical markers are currently available. Recent cDNA microarray studies revealed the pleckstrin homology‐like domain, family A, member 1 protein (PHLDA1) as a highly reliable marker of the hair follicle stem cells. Given the differentiation of trichoepithelioma along the follicular lineage and the proposed role of PHLDA1 as a follicular stem cell marker, we examined the staining pattern of PHLDA1 in the desmoplastic variant of trichoepithelioma and in its differential diagnostic conundrum, morphoeic BCC. Objectives To describe the expression pattern of PHLDA1 in morphoeic BCC and desmoplastic trichoepithelioma. Methods Evaluation of the staining pattern for PHLDA1 was performed using standard immunohistochemical techniques. For comparison reasons, we analysed staining for PHLDA1 in normal skin structures with particular reference to the hair follicle. Results With the exception of one case, all 16 desmoplastic trichoepitheliomas were immunoreactive with more than 80% of the cells stained, whereas all 14 morphoeic BCCs were PHLDA1‐negative with the exception of ulcerated tumours. In the latter, the tumour islands close to the ulcer were PHLDA1‐positive whereas the deeper located tumour portions remained immunonegative. PHLDA 1 was prominently expressed in the hair follicle bulge of terminal and vellus hair follicles. Conclusions The hair follicle bulge marker PHLDA1 differentiates between desmoplastic trichoepitheliomas and nonulcerated examples of morphoeic BCCs. We suggest incorporating PHLDA1 in the diagnostic work‐up of difficult to differentiate basaloid tumours.     

Desmoplastic sebaceoma arising from nevus sebaceus: a new variant

Nevus sebaceus is known to have the potential to develop into various secondary tumors. We observed a sebaceoma arising from a nevus sebaceus excised from the left cheek of a 51‐year‐old woman. This sebaceoma showed desmoplastic change similar to that observed in desmoplastic trichoepithelioma and desmoplastic trichilemmoma. This heretofore undescribed desmoplastic variant of sebaceoma should not be mistaken for invasive sebaceous carcinoma.     

Differentiation between basal cell carcinoma and trichoepithelioma by immunohistochemical staining of the androgen receptor: an overview

Clinical and histopathological differentiation between basal cell carcinoma (BCC) and trichoepithelioma (TE) is a frequent problem. Attempts have been made to identify immunohistochemical markers helpful in differentiating them. A correct diagnosis is important because the tumours are treated differently. Recent studies showed the absence of androgen receptor (AR) expression in benign hair follicle tumours like TE. This study examines whether AR immunostaining is a useful diagnostic test to differentiate between BCC and TE. We randomly selected 75 cases with histological diagnoses of either BCC (subtypes: superficial, nodular or infiltrative) or TE (subtypes: classic or desmoplastic) from the database of the pathology department of Maastricht University Medical Centre. The available haematoxylin & eosin (H&E) slides were reviewed by three independent investigators using predetermined characteristics. Fifty-six slides (38 BCC and 18 TE) with unequivocal histological characteristics of either tumour were used for immunohistochemistry with AR antibodies. Any nuclear expression within the tumour was considered positive. AR expression was present in 5/8 classic TE, 0/10 desmoplastic TE, 22/23 superficial or nodular BCC and in 10/15 infiltrative BCC. Immunohistochemical stain for AR is useful to differentiate between TE and BCC; particularly in desmoplastic TE versus infiltrative BCC (specificity and positive predictive value of 100%).     

Trichoadenoma associated with an intradermal melanocytic nevus: a combined malformation

Melanocytic nevi have been associated with epidermal hyperplasia, adnexal hyperplasia with follicular and sebaceous differentiation, cysts, and tumors of epidermal or adnexal origin. We report a combined cutaneous hamartoma in a 29-year-old woman that comprised a trichoadenoma within an intradermal melanocytic nevus. Clinical diagnosis was a malignant transformation of a melanocytic nevus. Histopathologically, multiple keratinous cysts together with solid islands or masses of eosinophilic epithelial cells were closely intermingled with the nevus cells. Occasional nests of basaloid cells were present. Although to our knowledge this association has not been previously reported, it is worth considering that trichoadenoma and desmoplastic trichoepithelioma are the two ends of a spectrum of lesions. This combined hamartoma reported herein is important because growth of these lesions could be clinically misinterpreted as malignant transformation of a preexisting lesion. Histologic study will reveal the correct diagnosis in such cases.     

结缔组织增生性毛发上皮瘤一例

报告1例结缔组织增生性毛发上皮瘤并文献复习.患者女,76岁,左上唇淡红色浅碟状斑块10年余.皮肤科情况:左上唇见淡红色浅碟状斑块,直径约1 cm,斑块边缘轻度隆起,表面光滑,质硬.组织病理学检查示真皮胶原纤维明显增生,其间有散在的角质囊肿和基底样细胞条索.     

结缔组织增生性毛发上皮瘤1例

报告1例结缔组织增生性毛发上皮瘤。患者女,40岁。头皮斑块1年余就诊。皮肤科检查：头顶部有一直径约1.5cm大淡红色环形斑块,边缘轻度隆起,表面光滑,质硬,无毛发生长。组织病理学检查示表皮轻度增生,真皮浅层可见多数大小不一的角质囊肿和嗜碱性细胞条索,周围胶原纤维明显增生,该例患者的临床表现及组织病理学改变均符合结缔组织增生性毛发上皮瘤。     

Desmoplastic trichoepithelioma. Clinical aspects, histology and differential diagnosis

Twelve desmoplastic trichoepitheliomas (DT) including one recurrent tumor from 9 patients are described by their clinical and histopathological features with special reference to the differential diagnostic aspects. DT typically appear as dimple lesions with raised edges in the faces of young females and histologically is composed of epithelial sheets and keratinized or calcified cysts in a desmoplastic stroma. A case showing cellular pleomorphism and followed by a relapse may represent an aggressive variant of DT. DT must be distinguished from syringoma, trichoepithelioma and especially basal cell carcinoma (BCC).     

Criteria for histologic differentiation of desmoplastic trichoepithelioma (sclerosing epithelial hamartoma) from morphea-like basal-cell carcinoma

Histological differentiation between desmoplastic trichoepithelioma and morphea-like basal-cell carcinoma may be exceedingly difficult. Because the criteria for this differentiation published to date have not proved satisfactory to us, we undertook a study with the aim of formulating repeatable and reliable criteria for distinguishing between these two conditions of wholly different biological potential. We believe that the 26 sets of criteria listed here will permit reliable differentiation of desmoplastic trichoepitheliomas from morphea-like basal-cell carcinomas, even in biopsy specimens taken by shave and punch techniques.     

Microcystic adnexal carcinoma with multiple areas of follicular differentiation toward germinative cells and specific follicular stroma (trichoblastomatous areas)

We present a case of microcystic adnexal carcinoma (MAC) occurring on the upper lip of a 63-year-old man, which, in addition to the predominant areas of a conventional MAC, manifested multiple foci of follicular differentiation resulting in trichoblastomatous appearances. Some areas were highly reminiscent of desmoplastic trichoepithelioma (columnar trichoblastoma). We also reviewed 24 cases of MAC in our files, but in none of the cases were similar features observed, indicating that such histopathological findings are rare in MAC.