Desmoplastic Trichoepithelioma Research Articles

Collision tumour of desmoplastic trichoepithelioma and melanocytic compound nevus.

Collision tumour of desmoplastic trichoepithelioma and melanocytic compound nevus.

Multiple Nonfamilial Trichoepitheliomas: A Rare Case with Review of the Literature

Trichoepitheliomas are benign tumors of follicular origin and often appear in childhood or early adolescence. They present as small, firm papulonodular lesions of normal skin color or translucent. The lesions gradually increase in size and then stabilize. They sit electively on the face, mainly in the nasolabial folds, on the forehead, chin, and cheeks, and sometimes on the scalp and neck. Trichoepitheliomas can be divided into three subgroups: multiple familial Trichoepitheliomas, solitary non-hereditary Trichoepitheliomas, and desmoplastic Trichoepitheliomas. Nonfamilial multiple trichoepitheliomas are rarely described. We report a case of a 12-year-old child whose clinical history and clinicopathologic correlation allowed us to retain the diagnosis of multiple non-familial trichoepitheliomas.

Nodulo-Ulcerative Plaque Over the Vertex of Scalp.

A 45-year-old man presented with a 12-year-old swelling in the vertex region of his scalp that had gradually grown in size for the last few years. Pus discharge and minor pain had been present for the previous 10 days. Patient had received treatment with oral and topical antibiotics. There was no history of preceding trauma, nevoid lesions, or associated comorbidities. Cutaneous examination revealed a hard non-tender fixed plaque of 3 cm × 2 cm size over vertex area of scalp with central ulceration and yellowish white discharge. It was separated from surrounding skin with a sharp demarcation [Figure 1]. There was no regional lymphadenopathy.Figure 1: Single hard, non-tender fixed plaque of 3 cm × 2 cm size over vertex area of scalpSkin biopsy from the lesion revealed an epithelial neoplasm in the dermis reaching up to the base and both lateral margins without any connection with the epidermis [Figure 2]. Upper dermis and mid-dermis showed numerous dilated keratin cysts and orthokeratotic corneocytes [Figure 2]. Mid- and lower dermis showed numerous small rounded and elongated tumor islands made up of basaloid cells without too much atypia with ductal structures or differentiation at their center and surrounded by dense fibroblastic stroma. Some of these ducts were elongated and dilated but were lined by cuboidal basaloid cells without any signs of apocrine differentiation [Figure 3].Figure 2: An epithelial neoplasm in the dermis reaching up to the base and both lateral margins but showing no connection with surface epidermis (H & E 40x)Figure 3: In the mid-dermis and lower dermis, the neoplasm shows numerous keratin cysts, many of which are dilated and show orthokeratotic corneocytes, majority of the tumor islands are small and rounded, while others are small irregular and surrounded by dense fibroblastic stroma, numerous rounded and elongated tumor islands made up of basaloid cells without too much atypia (H&E 100x)What is the diagnosis? Answer Microcystic adnexal carcinoma. Discussion Microcystic adnexal carcinoma (MAC) is a rare, slow-growing but locally aggressive malignant neoplasm with low mortality rate and it rarely metastasizes.[1] It arises from pluripotent keratinocytes and shows characteristic pilar and eccrine differentiation.[1] It was first described in 1982 by Goldstein et al. as a distinct clinicopathologic entity.[2] It is reported mainly in adults between 55 and 60 years of age with a slight female preponderance. Clinically, it presents as a solitary asymptomatic plaque or nodule most commonly on the head and neck areas. Occasionally, patients may present with pain, itching, burning sensation, numbness, and tingling as a result of perineural invasion by the tumor.[2] Immunosuppression, UV radiation exposure, and radiotherapy are the predisposing factors.[2] MAC is commonly misdiagnosed as desmoplastic trichoepithelioma (DT), syringoma, morpheaform basal cell carcinoma (mbcc), and desmoplastic squamous cell carcinoma (SCC) on histopathology.[3] It is often difficult to clinically distinguish MAC from other skin-colored growths on the head and neck including BCC. Histopathologically, the presence of ductal structures helps to differentiate MAC from DT, whereas the presence of calcification, prominent horn cysts, and single-file strand formation differentiates MAC from syringoma. Among all these tumors, perineural and subcutaneous involvement is characteristic feature of MAC on histopathology. MAC is also characterized by presence of normal tissue between epidermis and dermis.[4] Immunohistochemical markers that help to distinguish MAC from morpheaform BCC and SCC include cytokeratin 15 (CK15), carcinoembryonic antigen (CEA), and BerEP4 [Table 1].[5]Table 1: Immunohistochemical markers to distinguish MAC from morpheaform BCC and SCCThe most definitive treatment for MAC is complete surgical excision. Mohs micrographic surgery (MMS) is the preferred option as it is associated with low recurrence rate.[6] MAC has a high recurrence rate that ranges from 15% to 60% depending on the treatment option used. Recurrence may occur many years following the excision; hence, long-term follow-up is mandatory. Other treatment options include wide local excision, adjuvant or definitive radiotherapy, and chemotherapy.[7] Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Desmoplastic trichoepithelioma: an uncommon adnexal tumour with a predilection for cosmetically sensitive sites.

Desmoplastic trichoepithelioma: an uncommon adnexal tumour with a predilection for cosmetically sensitive sites.

Does Immunohistochemistry Add to Morphology in Differentiating Trichoepithelioma, Desmoplastic Trichoepithelioma, Morpheaform Basal Cell Carcinoma, and Microcystic Adnexal Carcinoma?

The distinction among cutaneous basaloid neoplasms such as trichoepithelioma (TE), desmoplastic trichoepithelioma (DTE), morpheaform basal cell carcinoma (MBCC), and microcystic adnexal carcinoma (MAC) can be difficult, especially in superficial biopsies. As the treatment plan of each entity is different, accurate characterization is important for appropriate management. While TE and DTE are benign neoplasms with indolent behavior, MBCC and MAC are typically locally aggressive. The expression of several recently described immunohistochemical (IHC) markers, including p40, IMP3, and ProEx C, has not been adequately established in cutaneous neoplasms. We explored the potential utility of a broad IHC panel, including previously reported and novel markers to differentiate TE, DTE, MBCC, and MAC. A total of 35 archival cases [TE (n=14), DTE (n=9), MBCC (n=6), and MAC (n=6)] were stained with 9 IHC markers: p40, IMP3, ProEx C, p16, CK20, Ki-67, androgen receptor, D2-40, and beta-catenin. Tumors with >5% immunoreactivity were scored as positive. The intensity was scored on a scale from 1+ to 3+. The pattern of positivity- nuclear, cytoplasmic, membranous, or in combination; peripheral or central distribution with lesion was also recorded. CK20 (in contrast to prior studies) and IMP3 were negative in all cases. Likewise, with the exception of one case of TE, androgen receptor showed no immunoreactivity in all categories. No significant difference was observed in the expression of beta-catenin, p16, ProEx C, and p40 among the four groups of cutaneous neoplasms. The mean Ki-67 labeling index for MBCC (8%) was slightly higher than DTE (3%). Interestingly, the proliferation index for TE (15%) was significantly higher than that of MBCC. All six cases of MAC and 36% of TEs expressed D2-40; neither the MBCC nor DE cases showed D2-40immunoreactivity. Also, we confirmed the previously published observation of scattered CK20 positive Merkel cells in the epidermis of all cases of DTE; whereas, no Merkel cells were identified in MBCC and MAC cases. Except Ki-67, our IHC panel showed no significant added diagnostic utility of IHC in discriminating among TE, DTE, MBCC, and MAC. Among the four cutaneous neoplasms, DTE and MBCC show a small but discernible difference in Ki-67.

A Case of Desmoplastic Trichoepithelioma with a New Dermoscopy Finding.

A Case of Desmoplastic Trichoepithelioma with a New Dermoscopy Finding.

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

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.

Desmoplastic Trichoepithelioma: An Unusual Location

Desmoplastic trichoepithelioma is a rare benign tumor emerging from the hair follicle. Here, we report an unusual nasal location of a desmoplastic trichoepithelioma in a female patient

Morpheaform Basal Cell Carcinoma Masquerading as Desmoplastic Trichoepithelioma in a Young Patient.

Morpheaform Basal Cell Carcinoma Masquerading as Desmoplastic Trichoepithelioma in a Young Patient.

Glioma-Associated Oncogene-1 Expression in Basal Cell Carcinoma and Its Histologic Mimics.

Basal cell carcinoma (BCC) is the most common skin cancer, and it has numerous histologic mimics with variable prognoses and treatments. Although some immunohistochemical stains can be used for the differential diagnosis of BCC, variability and overlap in results can complicate their interpretation. Immunohistochemical staining for glioma-associated oncogene-1 (Gli-1) was performed on 26 nodular BCCs, 22 infiltrative BCCs, 9 basaloid squamous cell carcinomas, 12 desmoplastic trichoepitheliomas, 19 Merkel cell carcinomas, 11 sebaceous carcinomas, 10 cylindromas, 14 spiradenomas, 12 adenoid cystic carcinomas (AdCC), and 1 solitary trichoepithelioma. Strength of staining was scored as 0, 1+, 2+, or 3+, and distribution of staining was categorized as diffuse, multifocal, or focal. Strong, diffuse Gli-1 expression was seen in all tumors with basal epidermal-type differentiation, including BCC, trichoepithelioma, and basaloid squamous cell carcinoma. All examples of Merkel cell carcinoma were negative for cytoplasmic expression. Seven out of 11 sebaceous carcinomas were negative for Gli-1, and the remaining 4 showed 1+ expression. Cylindroma, spiradenoma, and AdCC, each an adnexal skin tumor, showed the most variable staining, but with cylindroma and spiradenoma demonstrating comparable labeling patterns. Overall, although Gli-1 may not distinguish between basal epidermal-type tumors, it may have a role in separating that group from lesions with adnexal differentiation, particularly sebaceous carcinoma, but also cylindroma, spiradenoma, and AdCC. Any cytoplasmic staining seems to exclude the diagnosis of Merkel cell carcinoma.

Collision Tumor in the Lower Eyelid: Basal Cell Carcinoma Adjacent to Trichoepithelioma.

The coexistence of 2 neoplasms in a single cutaneous specimen is unusual. We describe a lower eyelid lesion in which the biopsy revealed a trichoepithelioma (TE) and an adjacent basal cell carcinoma (BCC). A 57-year-old female patient reported a 5-year history of lower eyelid pruritus and had been treated for blepharitis elsewhere. She was referred for eyelid evaluation due to the presence of a plaque, loss of eyelashes, and areas of inflammation in the right lower eyelid. She underwent tumor excision, and the eyelid was reconstructed using an orbicularis muscle advancement flap combined with a free tarsoconjunctival graft and a skin graft. Preoperative photographs show an extensive lesion, with madarosis in the right lower eyelid (Fig. A and B). Biopsy specimen from the right lower eyelid revealed 2 different tumor types: a TE and an adjacent BCC (Fig. C and D). A focus of TE is seen (left) juxtaposed with a focus of BCC (right). The area containing the TE was composed of basaloid cell nests and horn cysts, embedded within an organized stroma. Areas of cicatricial fibrosis and foreign body-type reaction were also observed. These histopathology features were consistent with that of a desmoplastic TE (DTE). The adjacent BCC area showed proliferation of atypical basaloid cells with peripheral palisading. Cytoplasm was basophilic and relatively scant, nuclei were large and mildly irregular, and contained grumous chromatin and mitotic figures. Trichoepithelioma is a benign tumor of follicular origin with 3 distinctive variants: multiple familial, solitary, and DTE. DTE is a rare benign adnexal tumor, derived from basal cells in the outer root sheath of the hair follicle, histologically characterized by narrow strands of basaloid tumor cells, keratinous cysts, and a desmoplastic stroma. TEs and BCCs both present with nests of basaloid cells. Histologic features that favor TE include the following: architectural symmetry, horn cysts, and associated giant cell reaction (rare in BCC), papillary mesenchymal bodies, no high-grade atypia, no or very low mitotic activity, monomorphic nuclei, no tumor necrosis, no peripheral clefting. The presence of peripheral palisading of basaloid cells, clefting between the epithelial and stromal components, necrosis, and high mitotic activity are associated with BCC. When histologic examination does not permit to differentiate a TE from a BCC, immunohistochemical stains, such as BCL2, CD10, CD34, AR, may be useful. Transformation of TE to BCC is rare and usually occurs in the setting of multiple TEs. A possible way to investigate transformation would be to compare the DNA of both tumors to find a common mutation. In our patient, it is more likely that this is a collision tumor (coexistence of 2 different tumors in the same lesion). Concomitant presence of a TE and a BCC is rare, and, to the best of our knowledge, this is the only case showing a DTE adjacent to a BCC, involving the eyelid. This case highlights that benign and malignant pathology can coexist within the same lesion. Special attention should be addressed to collision tumors since, in these cases, a small incisional biopsy might not be sufficient for accurate diagnosis.Fig.: Basal cell carcinoma adjacent to trichoepithelioma. A and B, A 57-year-old female patient presented an extensive lesion, with madarosis in the right lower eyelid. C and D, Hematoxylin and eosin stain of the biopsy specimen (100× and 200×) revealed 2 different tumor types: a focus of trichoepithelioma is seen (left) juxtaposed with a focus of basal cell carcinoma (right).

Desmoplastic Trichoepithelioma: Histopathologic and Immunohistochemical Criteria for Differentiation of a Rare Benign Hair Follicle Tumor From Other Cutaneous Adnexal Tumors.

Desmoplastic trichoepitheliomas (DTEs) are benign cutaneous neoplasms that originate from the hair follicle and exhibit a preference for the facial region. This type of neoplasm is characterized by accelerated growth, with vigorous histologic and immunohistochemical features that may be confused with other skin cancers. Thus, the objective of this study is to establish a definitive diagnosis that can be widely used. This review was systematically carried out and includes case series and studies to establish valuable data that can be used for research. The articles were sought in PubMed, MEDLINE, and Google Scholar using the keywords “desmoplastic trichoepithelioma,” “morphea basal cell carcinoma,” “microcystic adnexal carcinoma,” “syringoma,” and “cutaneous breast carcinoma.” From a total of 65 journal articles, we chose 42 studies describing the clinical features, etiology, histopathology, and immunohistochemical characteristics of tumors. After quality assessment, 10 studies were selected, representing the differentiating features among the four mentioned cutaneous tumors. The differential diagnosis of DTE also includes other cutaneous and follicular tumors. At present, there is no standardized grading system for trichogenic tumors, although several symptomatic terms have been offered. More recently, immunohistochemistry and histopathological studies support the differentiation between the above-mentioned cutaneous tumors. However, additional research needs to be conducted to obtain complete information regarding the specific distinct traits of the indicated cutaneous tumors.

The Follicular Benignancy- Desmoplastic Trichoepithelioma

Trichoepithelioma is a benign, cutaneous neoplasm originating from the hair follicle and is categorized into singular trichoepithelioma, multiple trichoepithelioma and desmoplastic trichoepithelioma wherein desmoplastic trichoepithelioma is cogitated as an exceptional, cutaneous adnexal tumour. Desmoplastic trichoepithelioma was initially scripted by Hartzell in 1904 wherein the lesion was described as a benign, cystic epithelioma. Desmoplastic trichoepithelioma can be additionally nomenclated as epithelioma adenoides cysticum, morphea - like epithelioma or sclerosing epithelial hamartoma 1. Familial instances of desmoplastic trichoepithelioma are infrequent and can be misdiagnosed on account of adjunctive benign, cutaneous, adnexal neoplasms depicting subtle clinical features, excepting a nodular basal cell carcinoma. Cogent clinical and histological features can assist the diagnosis of desmoplastic trichoepithelioma 1, 2.

Trichoadénome : description anatomoclinique et dermatoscopique

Trichoadenoma is a very rare follicular tumour with a remarkable histopathological appearance. In this article we present a series of 12 cases of trichoadenoma, as well as the anatomoclinical and dermatoscopic findings in a typical case. We discuss these findings in the light of an extensive literature research. We collated 12 cases of trichoadenoma of indisputable diagnosis made at the dermatopathology laboratory of the Dermatological Clinic of the University Hospitals of Strasbourg over a 30-year period (1989-2018). The 12 cases comprised 7 women and 5 men, of average age 58.9 years, the majority having lesions on the cephalic extremity followed by the buttocks and thighs. Histopathological examination, which was similar in all 12 cases, showed multiple epidermal cysts containing an eosinophil lamellar keratin with a stratified wall without any visible hair, located in the superficial and mid dermis and appearing to be stacked on top of one another. In immunohistochemistry, broad spectrum keratin markers were still positive, the follicular marker Ber-EP4 weakly expressed and PHLDA1 was negative. For the case examined using polarized-light dermatoscopy, small rounded white-yellow areas were observed corresponding to cystic structures surrounded by irregular linear vessels. Trichoadenoma is a rare tumour seen in middle-aged adults of mean age 45 years, and has no sexual predominance. It is asymptomatic, slow-growing, variable in colour, measures less than one centimeter and is most often located on the face or buttocks. In terms of histology, the juxtaposition of multiple small cystic structures suggests a follicular origin. Differential diagnosis is made with trichoblastomas, which always intensely express PHLDA1 and/or Ber-EP4, desmoplastic trichoepithelioma, which consists of multiple much thinner spans in a highly fibrous stroma with clearly visible arborescent vessels over a white-yellow ivory background at dermatoscopy, microcystic carcinoma, which has a deeper extension, and plaque milium, in which the cysts are larger.

State of the art of Mohs surgery for rare cutaneous tumors in the Spanish Registry of Mohs Surgery (REGESMOHS).

The use of Mohs micrographic surgery (MMS) for rare cutaneous tumors is poorly defined. We aim to describe the demographics, tumor presentation and topography, surgery characteristics and complications of MMS for rare cutaneous tumors in a national registry. Prospective cohort study of patients treated with MMS in Spain between July 2013 and June 2018. The inclusion criteria were patients with cutaneous tumors with final diagnosis different from basal cell carcinoma, squamous cell carcinoma, dermatofibrosarcoma protuberans, or any kind of melanoma. Five thousand and ninety patients were recorded in the registry, from which only 73 tumors (1.4%) fulfilled the inclusion criteria: atypical fibroxanthoma (18), microcystic adnexal carcinoma (10), extramammary Paget's disease (7), Merkel cell carcinoma (5), dermatofibroma (4), trichilemmal carcinoma (4), desmoplastic trichoepithelioma (4), sebaceous carcinoma (3), leiomyosarcoma (2), porocarcinoma (2), angiosarcoma (2), trichoblastoma (1), superficial acral fibromyxoma (1), and others (10). No intra-surgery morbidity was registered. Postsurgery complications appeared in six patients (9%) and were considered mild. Median follow-up time was 0.9years during which three Merkel cell carcinomas, one angiosarcoma, one microcystic adnexal carcinoma, and four others recurred (12.3%). This national registry shows that rare cutaneous tumors represent a negligible part of the total MMS performed in our country with a low complication rate.

Ln-γ 2 chain of laminin-332 is a useful marker in differentiating between benign and malignant sclerosing adnexal neoplasms.

Laminin (Ln)-γ 2, one of the chains of Ln-332, is a marker of invasive tumours and is frequently expressed as a monomer in malignant tumours. Desmoplastic trichoepithelioma (DTE), some types of basal cell carcinoma (BCC) (infiltrating and morphoeic BCC) and microcystic adnexal carcinoma (MAC) belong to a group of tumours known as sclerosing adnexal neoplasms (SAN) that are frequently difficult to differentiate and often require immunohistochemistry for diagnosis. The aim of this study was to assess the usefulness of Ln-γ 2 expression in the differential diagnosis of DTE, infiltrating/morphoeic BCC, MAC and syringoma. In this study, we compared the expression of Ln-γ 2 in infiltrating/morphoeic BCC (n=28), DTE (n=26), MAC (n=10) and syringoma (n=20). Immunohistochemically, Ln-γ 2 positivity was noted in 96% (27 cases) of infiltrating/morphoeic BCC and 90% (nine cases) of MAC, while all DTE and syringoma cases were negative. Furthermore, Ln-γ 2 expression pattern in infiltrating/morphoeic BCC was different from that in MAC. Ln-γ 2 expression was found in the cytoplasm of tumour cells in infiltrating/morphoeic BCC tumour cells, while in MAC linear expression was noted both along tumour nests and in the cytoplasm. Ln-γ 2 is a helpful adjunct in the differential diagnosis of SAN.

Cells to Surgery Quiz: December 2018

Cells to Surgery Quiz: December 2018

Cutaneous Squamous Cell Carcinoma With Sclerosing Features: An Uncommon and Potentially Aggressive Variant.

Sclerosing squamous cell carcinoma (SCC), also known as "desmoplastic" SCC, is a rare subtype of cutaneous malignancy. This variant is clinically significant because it is associated with an increased risk of local recurrence and metastasis. We herein present 16 examples of sclerotic SCC of the skin in 8 men and 3 women, with a median age of 66 years. The most common site of origin for this tumor is the skin of the head and neck, including the scalp (5 tumors in 2 different patients), forehead (3 cases), nasal ala (2 cases), neck (2 cases in the same patient), ear (2 cases), cheek (1 case), and chest (1 case). Microscopically, sclerosing SCCs are characterized by cellular cords, nests, and islands, as well as scattered single cells infiltrating densely desmoplastic and collagenized connective tissue. The differential diagnosis principally includes sclerosing basal cell carcinoma, microcystic adnexal carcinoma, and desmoplastic trichoepithelioma. The main goals of this study are to further characterize these lesions pathologically, and increase general awareness of this SCC subtype.

Desmoplastic trichoepithelioma complicated by sebaceous hyperplasia: a case report

A 67-year-old male patient presented with a plaque on the top of the head for more than 1 year. Physical examination showed an annular pale red plaque sized about 1.5 cm × 1 cm on the top of the head. It had a depressed center and papule-like elevated faint yellow boundaries, and there was no hair on the surface of the lesion. Histopathologic examination revealed milder epidermal hyperplasia, a small area of epidermal depression, confluence and hyperplasia of multiple sebaceous glands in the dermis, many keratinous cysts and funicular basophilic epithelial cells surrounded by hyperplastic collagen fibers in the superficial dermis. Immunohistochemical study showed positive staining for CD34 (hair mesenchymal cells) , epithelial membrane antigen (EMA) , cytokeratin 20 (CK20) , but negative staining for bcl-2, P53, CD56 and collagen Ⅳ, with the proliferation index Ki-67 of 2% - 5%. Based on the pathological results, the patient was diagnosed with desmoplastic trichoepithelioma complicated by sebaceous hyperplasia. Key words: Sebaceous gland diseases; Desmoplastic trichoepithelioma

Differential diagnostic significance of epithelial and stromal CD10 expression in tumors of trichogenic origin.

The histological differential diagnosis between benign trichogenic skin tumors and basal cell carcinoma may be challenging. We therefore set out to investigate whether expression of CD10, a cell surface protein with neutral endopeptidase activity, might be a suitable marker for the histological differential diagnosis of trichogenic skin tumors. We immunohistochemically analyzed 119 cases of benign trichogenic skin tumors and basal cell carcinoma. These included 28 nodular and 15 sclerosing basal cell carcinomas, 21 Pinkus tumors, 20 trichoblastomas, nine trichofolliculomas, eleven trichoepitheliomas, five desmoplastic trichoepitheliomas, and ten seborrheic keratoses. The majority of nodular basal cell carcinomas expressed CD10 in tumor cells at the peripheral (22/28 [75%]). On the other hand, trichoblastomas revealed peripheral CD10 expression in only 10% (2/20) of cases, whereas 50% showed central expression (10/20). Peripheral epithelial expression of CD10 was also found in Pinkus tumors (9/21 [42.9%]) and trichoepithelioma (4/11 [36.4%]). Desmoplastic trichoepithelioma showed no tumoral CD10 expression at all (0/5 [0%]), while the majority of sclerosing basal cell carcinomas was positive for CD10 (13/15 [86.7%]). Our findings suggest that epithelial expression of CD10 -and not peritumoral stromal CD10 expression, as has been postulated -may well be of differential diagnostic significance. The pattern of distribution of CD10-positive neoplastic cells in particular can be useful in the diagnosis of trichogenic tumors.