Case (Image) Link: click here

Trichoepithelioma is regarded as a poorly differentiated hamartoma of the hair germ.

Although most classifications include this as a separate entity Ackerman and his colleagues have suggested that such tumours should be grouped together with trichoblastomas and use the term "trichoblastoma" for all tumours showing predominant hair germ differentiation.

Site:  Commonly located on the head and neck region. Solitary- Nose, upper lip and cheeks. Multiple- Central part of the face, trunk, neck & scalp.

Clinical presentation: Skin coloured papules. May be solitary or multiple. Papules may coalesce to form plaques. Rare presentation is a linear form.

Multiple tumours (epithelioma adenoides cysticum) inherited as autosomal dominant.

Brooke-Spiegler syndrome: Multiple trichoepitheliomas and cylindromas.

Microscopic features : Well circumscribed dermal tumour ; Islands,  nests and cords of uniform basaloid cells ; Cells are set in a variably cellular fibrous stroma ; Epithelial structures resemble hair papillae or abortive hair follicle ; Small keratocysts (infundibular differentiation) lined by stratified squamous epithelium ; Retraction of stroma from adjacent dermis ; Foci of calcification are often present ; Few mitotic figures and apoptotic bodies.

Immature trichoepithelioma:  Typically exhibits no horn cysts, displays fewer primitive hair structures, and lacks the adenoidal growth patterns of the tumour lobules which are usually present in the classical trichoepitheliomas.

Differential diagnosis :

1. Basal cell carcinoma;  Distinction from some types of basal cell carcinoma has been based on the paucity of mitoses and apoptotic bodies, lack of retraction between stroma and epithelium and presence of primitive follicles in trichoepithelioma and differences in CD34 and bcl2 expression. However, there are some tumours in which this distinction cannot be reliably made.   

2. Microcystic adnexal carcinoma ; 

4. Trichoadenoma ;  5.Trichoblastoma ;

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CaseLink

Clinical image(DermAtlas):

DESMOPLASTIC TRICHOEPITHELIOMA:  Image:

Desmoplastic trichoepithelioma is a benign neoplasm considered to have follicular differentiation. Its sweat gland- or sebaceous-lines of differentiation have been also reported.

The cells in desmoplastic trichoepithelioma are suggested to be in close association with the basal cells in the outer root sheath.

Diagnosis of this lesion is important because it may be mistaken for Microcystic adnexal carcinoma clinically and histologically.

This condition should not be diagnosed on shave, curettage or punch biopsies. Deep biopsy is necessary to identify subcutaneous  involvement.

Clinical presentation:  Presents as a solitary , small indurated often depressed plaque on the face.

Microscopic features:  Symmetrical well-circumscribed ;   Lesions are usually located in the mid and upper dermis ; Tumour consists of cords and small nests of uniform basaloid cells in a dense fibrotic stroma ; Superficially, small horn cysts and keratin granulomas may be present ; No ductal differentiation.

Differential diagnosis: 

1.Syringoma - Usually periorbital and multiple lesions ; Narrow strands of tumour cells ;  Horn cysts, foreign body granuloma or calcifications are rare.

2.Morpheic basal cell carcinoma - Form clefts between the nests and the stroma ; Coexisting nodular basal cell carcinoma; Mitoses and apoptotic bodies are common;  Foreign body granulomas and ruptured keratinous cysts are rare.

3.Microcystic adnexal carcinoma: click 

4.Metastatic breast carcinoma

Abstracts:

Androgen receptor expression helps to differentiate basal cell carcinoma from benign trichoblastic tumors.Am J Dermatopathol. 2005 Apr;27(2):91-5.

Eyelid trichoepithelioma--report of 2 cases.Arq Bras Oftalmol. 2005 Jan-Feb;68(1):136-9. Epub 2005 Mar 30.

Proliferative characterization of basal-cell carcinoma and trichoepithelioma in small biopsy specimens.J Cutan Pathol. 2004 Sep;31(8):550-4.

Multiple familial trichoepithelioma caused by mutations in the cylindromatosis tumor suppressor gene.Cancer Res. 2004 Aug 1;64(15):5113-7.

Two cases of desmoplastic trichoepithelioma.J Dermatol. 2004 Oct;31(10):824-7.

Immunohistochemical and ultrastructural observations of desmoplastic trichoepithelioma with a special reference to a morphological comparison with normal apocrine acrosyringeum.J Cutan Pathol. 2002 Jan;29(1):15-26.

Multiple familial trichoepitheliomas: a folliculosebaceous-apocrine genodermatosis.Am J Dermatopathol. 2002 Oct;24(5):402-5.

Expression of p27kip1 in Basal Cell Carcinomas and Trichoepitheliomas. Am J Dermatopathol 2002Aug;24(4) :313-8

Trichoepithelioma with "monster" stromal cells. J Cutan Pathol 2001 Aug;28(7):379-82

Sporadic trichoepithelioma demonstrates deletions at 9q22.3.Arch Dermatol. 2000 May;136(5):657-60.

An immunohistochemical study of basal cell carcinoma and trichoepithelioma. Am J Dermatopathol 1999 Aug;21(4):332-6

Trichoepithelioma: a 19-year clinicopathologic re-evaluation. J Cutan Pathol 1999 Sep;26(8):398-404

Immunohistologic differential diagnosis of basal cell carcinoma, squamous cell carcinoma, and trichoepithelioma in small cutaneous biopsy specimens. J Cutan Pathol 1998 Mar;25(3):153-9

The gene for multiple familial trichoepithelioma maps to chromosome 9p21.J Invest Dermatol. 1996 Jul;107(1):41-3

Merkel cells are integral constituents of desmoplastic trichoepithelioma: an immunohistochemical and electron microscopic study. J Cutan Pathol 1995 Oct;22(5):413-21

CD34 staining pattern distinguishes basal cell carcinoma from trichoepithelioma. Arch Dermatol 1994 May;130(5) :589-92