Basal cell carcinoma overlying a dermatofibroma: a revisited controversy

ARTICLE

Auteur(s) : Aristóteles ROSMANINHO¹ arisrosmaninho@gmail.com, Pedro FARRAJOTA², Carlos PEIXOTO², Isabel AMORIM¹, Manuela SELORES¹

¹ Department of Dermatology,

² Anatomopathology, Centro hospitalar do Porto-HSA, Serviço Dermatologia, Edifício Consultas Externas-HSA (Ex-CICAP), Rua D. Manuel II s/n^o, 4099-001 Porto, Portugal

A 47-year-old man presented with a 2-year history of a non-painful lesion on his right knee. The lesion had gradually enlarged overtime and a slight darkening was observed in recent months. He was otherwise asymptomatic. He denied any history of previous trauma and his medical history was unremarkable. On physical examination, a hard, well circumscribed, slightly erythematous, non-painful nodule, with a 1.2 cm diameter was localized on his right knee. A brownish coloration was noticed on the periphery of the lesion (figure 1A). Surgical excision of the lesion was performed and hematoxylin-eosin staining showed a nodular proliferation of mesenchymal spindle cells in storiform formation, entrapping collagen bundles in the reticular dermis. Some histiocytes and lymphocytes were also present. Overlying this lesion an epidermal proliferation of basaloid cells forming basaloid nests that focally infiltrated the reticular dermis were observed. These were limited by cells with peripheral palisade arrangement. The cells involved a mucinous stroma and pigment, retraction artifact and mitoses were also documented (figures 1B, C). Immunohistochemical staining with Ber-EP4 was positive at the areas of the basaloid proliferation (figure 1D). The diagnosis of a dermatofibroma and a basal cell carcinoma was made.

Dermatofibromas are benign dermal tumors that frequently exhibit a spectrum of epidermal acanthosis. Sometimes, significant basaloid proliferation is observed and, rarely, follicular and basal cell carcinoma-like changes are present [1, 2]. The association of dermatofibroma and basal cell carcinoma has rarely been reported and is controversial, since there are different opinions about the true reactive or neoplastic nature of the process. The basaloid proliferations have usually been considered to be the result of the inductive effect of a fibrohistiocytic proliferation of dermatofibroma cells on the epithelial cells of the hair follicle, favouring the hypothesis of a reactive process [2]. Some authors postulated that the epidermal induction phenomena are consequences of the compression of adnexal structures against the epidermis by the growing of the dermatofibroma or by some soluble substances, such as epidermal growth factor, which is produced by the dermal cells [3]. Nevertheless, Leong et al., suggested that the follicular induction seen with dermatofibromas may be related to PTCH gene inactivation, demonstrating that these two neoplasms can be genetically related [1]. A case of basal cell carcinoma and dermatofibroma occurring in a smallpox vaccination scar and a basal cell carcinoma overlying a histiocytoma have been recently reported [4, 5].

It seems that the superficial location, as well as the focal character of the lesion, the follicular differentiation and the absence of atypias and mitoses, are in favour of a benign process. In contrast, the young age of the patient, a lesion located to the trunk, the presence of basaloid nests down in the dermis, with a peripheral palisade arrangement of the nuclei and a mucinous stroma, as well as the presence of retraction artifacts, mitoses and pigment, seemed to favour a neoplastic origin [2, 5, 6].

Immunohistochemical studies have shown variable results and cannot distinguish between basaloid proliferations or basal cell carcinomas. In our case, basaloid nests with a peripheral palisade cell arrangement, a mucinous stroma, pigment, retraction artifact, mitoses and the focal invasion of the reticular dermis was observed, which led us to assume the coexistence of a basal cell carcinoma. The positive immunohistochemical staining for Ber-EP4 also favoured the malignant nature of the process, since this marker is seen in basal cell carcinomas. However, it also can be found on the outer root sheath of vellus anagen follicles, secretory coils of sweat glands, basaloid epithelium of tricoepitheliomas and follicular induction over dermatofibromas. The discussion around the reactive or neoplastic nature of this association remains controversial.

Disclosure

Financial support: none. Conflict of interest: none.

References

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2 HK Han, CH Huh, K.H. Cho Proliferation and differentiation of keratinocytes in hyperplastic epidermis overlying dermatofibroma. Immunohistochemical characterization Am J Dermatopathol 2001; 23: 90-98.

3 M Morgan, H Howard, M.A. Everett Epithelial induction in dermatofibroma. A role for the Epidermal Growth Factor (EGF) receptor Am J Dermatopathol 1997; 19: 35-49.

4 J.L. Curry Occurrence of a basal cell carcinoma and dermatofibroma in a smallpox vaccination scar Dermatol Surg 2008; 34: 132-134.

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