Advanced differentiation in trichoepithelioma and basal cell carcinoma investigated by immunohistochemistry against neurofilaments

Enemy in disguise: A case report of solitary trichoepithelioma initially diagnosed as BCC

INTRODUCTION

Solitary trichoepitheliomas (TE) are benign tumors that are strikingly similar to their malignant counterpart, basal cell carcinoma (BCC).

PRESENTATION OF CASE

An 83-year-old man presented with a 10-year history of a right lower lid skin mass initially diagnosed as BCC. Intraoperatively, an excisional biopsy was performed with primary reconstruction of the skin defect and the specimen was submitted for histopathology processing. Eventually, histopathology findings suggested the diagnosis of benign hair follicle tumor. The postoperative results were aesthetically pleasing and the integrity of the lower lid was preserved.

DISCUSSION

Despite being rare, benign solitary TE are frequently misdiagnosed as malignant BCC, and vice versa. Oculoplastic surgeons face considerable difficulty distinguishing the two pathologies due to their similar clinical and histological pictures. Hence, excisional biopsy should be considered whenever such discrepancy is confronted to avoid the possibility of recurrence or malignant transformation. Furthermore, immunohistochemical staining could increase the accuracy of diagnosis in such unequivocal findings.

CONCLUSION

Correlation of clinical, dermoscopic and histopathological findings are essential to establish an accurate diagnosis and select the appropriate management. In-depth understanding of eyelid reconstruction principles is mandatory to achieve desirable goals.

Trichoepithelioma and Basal Cell Carcinoma with Squamous Differentiation: Is it Causal or Coincidental?

Trichoepitheliomas (TEs) are benign cutaneous tumors that occur either as solitary non-familial or multiple familial. We report a case of multiple familial trichoepithelioma (MFT) in a 55-year-old female patient and her son who came with complaints of single ulcerated mass involving the left nasolabial fold and cheek. She had multiple papules and nodules all over the face and neck since 25 years. Histopathological examination of an ulcerated lesion revealed features of basal cell carcinoma (BCC) with squamous differentiation, which was confirmed by immunohistochemistry. A skin biopsy obtained from the papule on neck showed features of TE. However, whether BCC developed independently or by transformation from TE was uncertain. Her 36-year-old son presented with similar lesions on the face and a skin biopsy showed features of TE. Though malignant transformation of TE is quite rare, awareness of the potential for evolution of carcinoma in patients with MFT is important for management of these patients.

Fibroblast-activation protein: a single marker that confidently differentiates morpheaform/infiltrative basal cell carcinoma from desmoplastic trichoepithelioma

Microscopically, differentiating desmoplastic trichoepithelioma from morpheaform/infiltrative basal cell carcinoma can be difficult as both show 'islands and strands of basaloid cells embedded in a sclerotic stroma'. A superficial shave biopsy further compounds the diagnostic conundrum. Although a plethora of immunohistochemical markers have been touted as being of use as adjunct histologic tools, none thus far appears to be consistent and reliable in terms of specificity and/or sensitivity. Fibroblast-activation protein, a type II membrane-bound glycoprotein belonging to the serine protease family, is expressed in the granulation tissue of healing wounds. More recently, it has been identified as a marker of reactive tumor stromal fibroblasts, as it is reportedly selectively expressed in peritumoral stromal fibroblasts of multiple epithelial cancers including cutaneous malignancies such as basal cell carcinoma. Given this, we sought to ascertain the use of fibroblast-activation protein in distinguishing morpheaform/infiltrative basal cell carcinoma from desmoplastic trichoepithelioma. Immunohistochemical staining for fibroblast-activation protein was performed on desmoplastic trichoepithelioma (n=25) and morpheaform/infiltrative basal cell carcinoma (n=25), with the control group comprising scars from reexcision specimens (n=10). As expected, fibroblast-activation protein expression was observed in stromal fibroblasts of all control cases (10 of 10, 100%). Of interest, fibroblast-activation protein expression was observed in peritumoral fibroblasts of all cases of morpheaform/infiltrative basal cell carcinoma (25 of 25, 100%) but not in any cases of desmoplastic trichoepithelioma (0 of 25, 0%). A gradient of fibroblast-activation protein expression was observed in morpheaform/infiltrative basal cell carcinoma with more intense expression noted in fibroblasts abutting the tumor cells, a less intense expression in the distal peritumoral stromal portion, and minimal to loss of expression in adjacent normal tissue. In summary, findings from this study underscore the use of fibroblast-activation protein as a histologic adjunct in confidently differentiating morpheaform/infiltrative basal cell carcinoma from desmoplastic trichoepithelioma.