|LETTER TO EDITOR
|Year : 2022 | Volume
| Issue : 6 | Page : 221-223
Giant solitary trichoepithelioma: A diagnosis of exclusion
Nitin Krishna Patil1, Aditya Kumar Bubna1, Seeba Hussain1, Neha Singh2
1 Department of Dermatology, Katihar Medical College, Katihar, Bihar, India
2 Department of Pathology, Katihar Medical College, Katihar, Bihar, India
|Date of Submission||22-Jan-2021|
|Date of Decision||08-Mar-2022|
|Date of Acceptance||11-Mar-2022|
|Date of Web Publication||31-Jan-2023|
Aditya Kumar Bubna
Department of Dermatology, Katihar Medical College, Karim Bagh, Katihar - 854 106, Bihar
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Patil NK, Bubna AK, Hussain S, Singh N. Giant solitary trichoepithelioma: A diagnosis of exclusion. Int J Trichol 2022;14:221-3
Trichoepitheliomas (TEs) are regarded as poorly differentiated hamartomas of hair germ. There are three variants of TE, namely solitary, multiple, and desmoplastic. When a solitary TE is 2 cm or more in size, then it is labeled as giant solitary trichoepithelioma (GST).
GST is quite an uncommon appendageal tumor to permit a ready familiarity. We hereby report a case of GST, whose diagnosis was arrived primarily by the histopathological study as a diagnosis of exclusion, because both clinical and dermoscopic findings were not very conclusive for a single entity.
A 65-year-old female presented to the dermatology outpatient department with complaints of a slowly expanding asymptomatic lesion over the forehead for the past 10 months. It began as a minuscule pea-sized papule that slowly advanced to attain the current status [Figure 1]a. On examination, an indurated, annular plaque with asymmetric thickened borders was visualized. The border was broadened over the right margin with the thickening going on to enclose almost 80% of the plaque leaving behind a central depression of size 0.3 cm × 0.3 cm. Toward the upper and outer right border of the plaque, overlying crusting/scaling was seen. The left border was considerably thinner when compared to the right side [Figure 1]b. Palpation demonstrated a firm and nontender consistency. Clinical differentials of desmoplastic TE and sclerotic basal cell carcinoma (BCC) were considered. Dermoscopy revealed short, thick white crossing lines (consistent with chrysalis pattern), few telangiectatic vessels, circular white to cream-colored structures [Figure 2]a and yellowish-brown crusts and white scales along with arborizing vessels [Figure 2]b.
|Figure 1: (a) An annular sclerotic plaque on the forehead as seen on presentation (b) A closer view of the plaque demonstrating an asymmetrical thickening of the border with a crusted area on the right upper and outer aspect and a central depression|
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|Figure 2: (a) Dermoscopic evaluation showing a chrysalis pattern, along with telangiectatic vessels and circular white to cream-colored structures (b) Dermoscopic evaluation showing yellowish-brown crusting and white scaling along with arborizing vessels|
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Skin biopsy demonstrated an atrophic epidermis. Dermis was composed of islands of uniform basilar cells with peripheral palisading in few areas, and numerous keratinous cysts lined by stratified squamous epithelium. The basophilic cell nests lacked retraction clefts. Many of these nests demonstrated abortive hair follicle differentiation. The stroma exhibited a fibromyxoid consistency [Figure 3] and [Figure 4]. As facilities for cytokeratin markers were not available in our institute, this test could not be performed. Nevertheless, on careful evaluation of clinical, dermoscopic, and histopathological findings, a diagnosis of GST was finally arrived at.
|Figure 3: Histopathology demonstrating epidermal atrophy with aggregates of basaloid cells delineating abortive hair follicle differentiation to a high degree. One area illustrates early follicular stromal induction within nests of basaloid cells. Nests of basaloid cells lack retraction clefts. Furthermore, numerous horn cysts lined by stratified squamous epithelium can be observed (H and E, ×10)|
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|Figure 4: (a) Section demonstrates numerous horn cysts (straight black arrows) along with aggregates of basaloid cells (H and E, ×10) (b) Section illustrates aggregates of basaloid cells and the presence of a foci showing early follicular stromal induction within nests of aggregated basaloid cells (straight black arrow) (H and E, ×10) (c) Section elucidates numerous horn cysts surrounding which is a moderately dense lymphocytic infiltrate. A fibromyxoid stroma can be observed. Furthermore, aggregates of basaloid cells with peripheral palisading can be seen (curved black arrows) and a high degree of differentiation of basaloid cells toward follicular structures can also be observed (straight black arrows) (H and E, ×20)|
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Although the clinical morphology in our case was highly consistent with desmoplastic TE (illustrating the characteristic annular, indurated, and centrally depressed plaque); histopathology failed to demonstrate two components of the classical histopathological triad diagnostic for desmoplastic TE (viz. narrow strands of basaloid tumor cells and a desmoplastic stroma) as stated by Brownstein and Shapiro. Only one component of the triad, i.e., keratinous cysts was identified, thereby excluding its diagnosis.
Histopathology, in our case, elaborated a high degree of differentiation toward follicular structures along with numerous horn cysts and abortive dermal papillae. Also, the absence of mitotic figures and a noninfiltrative pattern on microscopy further pointed toward a diagnosis of solitary TE. The only finding causing doubt was the unusual clinical manifestation of the adnexal tumor. This sclerotic presentation of GST, we believe has not been previously reported and we therefore would like to highlight this new morphological pattern that we observed. Other rare phenotypes of GST that have been described in the past include subcutaneous nodules, pedunculated plaques, ulcerated forms, and cystic lesions.
Besides, we discovered that dermoscopy was not a very specific diagnostic tool here. Nevertheless, it enabled studying the underlying dermal pathology better. A number of findings overlapping with BCC/other skin adnexal tumors were identified in our dermoscopic evaluation and have been elaborated in [Table 1], which we consider to be of diagnostic value while evaluating adnexal tumors. However, histopathology still remains the gold standard for diagnosing these appendageal tumors, the strength of which can be enhanced by immunohistochemistry.
|Table 1: Analysis of dermoscopic patterns as seen in our case and in other conditions where such patterns could be encountered|
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Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]