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

Abstract

Basal cell carcinoma (BCC) and trichoepithelioma (TE) are sometimes diagnostic challenges for the pathologist in terms of their differential diagnosis. Although literature is quite rich in information about histologic and immunohistochemical clues to distinguish the differences between both, no single finding must be completely reliable. Moreover, some consider that TE is a better differentiated follicular tumour, while BCC represents a less developed stage in differentiation. For instance, the latter opinion is supported by the evidence of follicular papillae in TE. The formation of a perifollicular nerve plexus happens later than the formation of the follicular papillae in the development of a normal follicle. The study of the presence of the perifollicular nerve plexus in both tumours which could then provide us with evidence on the stage of differentiation of both tumours. 5 cases of TE and 10 cases of BCC were randomly selected from our archives and an immunohistochemical study for neurofilaments was performed in all the cases. We found a peritumoural nerve plexus in all the cases (TEs and BCCs). Since this plexus is a late sign of differentiation and since both types of neoplasias share it, we conclude that TE and BCC are both terminally differentiated neoplasms. The ability of BCC to infiltrate would have more to do with the acquisition by the tumour of such a property, rather than with a stage of indifferentiation.

Follicular stem cell marker PHLDA1 (TDAG51) is superior to cytokeratin‐20 in differentiating between trichoepithelioma and basal cell carcinoma in small biopsy specimens

“…Immunohistochemistry, if appropriately applied, can offer ancillary diagnostic support beyond that supplied by the evaluation of hematoxylin and eosin‐stained tissue sections. Numerous markers have been applied to this differential diagnostic setting, including bcl‐2, 3–8 Ki‐67, 8,9 proliferating cell nuclear antigen (PCNA), 8 lectins, 5,10,11 transforming growth factor‐beta, 4 stromelysin‐3, 12 p53, 8,9 p21, 9 CD10, 13 CD34, 4–6,14,15 Ber‐EP4 6,16 and neurofilament 17 . To date, cytokeratin‐20 (CK20), which highlights Merkel cells, has crystallized as the most useful marker 18–20 .…”

“…Numerous markers have been applied to this differential diagnostic setting, including bcl-2, 3 -8 Ki-67, 8,9 proliferating cell nuclear antigen (PCNA), 8 lectins, 5,10,11 transforming growth factor-beta, 4 stromelysin-3, 12 p53, 8,9 p21,9 CD10,13 CD34, 4 -6,14,15 Ber-EP4 6,16 and neurofilament. 17 To date, cytokeratin-20 (CK20), which highlights Merkel cells, has crystallized as the most useful marker. 18 -20 Typically, only trichoepitheliomas but not basal cell carcinomas harbor Merkel cells in their tumor islands, although there are exceptions.…”

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

“…This has thus driven an extensive effort to find an immunohistochemical marker of utility in differentiating the two. Immunohistochemical markers tested to date include CD34, 3,7-10 bcl-2, 3,9-12 CD10, 3,13 Ber-EP4, 10,14 androgen receptor (AR), 3,15,16 CK20, 3,16,17 stromelysin-3, 18 p53, 3,19,20 Ki-67, 3,19 p21, 19 transforming growth factor (TGF)-b, 21 lectins, 19,22 neurofilaments, 23 and p75 neurotrophin receptor. 24 None of these, to date, appears to be reliable in confidently differentiating desmoplastic trichoepithelioma from morpheaform/ infiltrative basal cell carcinoma (Table 1).…”

Giant solitary trichoepithelioma masquerading as basal cell carcinoma

“…2 MFTs are autosomal dominant affecting chromosome 9p21 with lesser expression and penetrance in a male. 1,6 The lesions of TE are characterized by firm skin-colored papules or nodules 2 to 8 mm in size, mainly concentrated around the nasolabial folds and forehead. The lesions first appear in childhood and may grow larger and increase in number over time.…”