Morpheaform Basal Cell Carcinoma Masquerading as Desmoplastic Trichoepithelioma in a Young Patient.

Sir,

We wish to describe a case of morpheaform basal cell carcinoma (mBCC) in a young patient with features of calcification and keratin cysts on histopathology and dermoscopy findings overlapping with desmoplastic trichoepithelioma (DTE).

A 26-year-old man presented with a slowly growing asymptomatic lesion over nose for the last 10 years. His medical history was otherwise unremarkable. On cutaneous examination, there was single well-defined skin-colored atrophic plaque of size approximately 2 cm × 1 cm with slightly elevated borders [Figure 1]. No other body site was affected. Dermoscopic examination revealed brownish pink background with arborizing vessels, multiple keratin cysts and chrysalis such as structures, black-brown dots, erosion, and whitish scales [Figure 2]. A skin biopsy revealed irregular strands of basaloid cells in a sclerotic stroma, peripheral palisading, horn cysts and calcification [Figure 3a and b]. Immunohistochemistry showed membranous and cytoplasmic expression of BerEp4 and strong nuclear expression of androgen receptor (AR). There was absence of CD34 staining in the stromal cells between the tumor islands and absence of CK 20 positive Merkel cell in the tumor islands. There was increased Ki-67 expression in tumor cells with proliferation index of 5-10% [Figure 4a–e]. Final diagnoses of morpheform BCC was made.

Figure 1

Single irregular shaped skin coloured to slightly pigmented atrophic plaque with slightly elevated borders present over nose

Figure 2

Dermoscopy (Dermlite™ DL4, 3Gen Inc., San Juan Capistrano, CA; 10× magnification; polarized mode) shows brownish pink background (brown arrow) with arborizing vessels (blue arrow), multiple keratin cysts (green arrow), chrysalis like structures (black arrow), multiple black brown dots (blue star), erosion (yellow star) and whitish scales

Figure 3

(a) Low power microphotograph shows irregular strands of cells in a sclerotic stroma, confined to superficial and mid-dermis. (Haematoxylin and Eosin, 20×). (b) Strands of basaloid cells with peripheral palisading and sclerotic stroma. Few horn cysts and calcification are also evident. (Hematoxylin and Eosin, 40×)

Figure 4

Immunohistochemistry for BCC. [a-E, 400×]. (a) Membranous and cytoplasmic expression of BerEp4. (b) Strong nuclear expression of Androgen receptor (AR). (c) Absence of CD34 staining in the stromal cells between the tumor islands. (d) No CK 20 positive Merkel cell in the tumor islands. (e) Increased Ki-67 expression in tumor cells with proliferation index of 5-10%

Discussion

Basal cell carcinoma (BCC) is the most common type of skin cancer. It rarely metastasizes; however, it is a cause of significant morbidity in patients. Various histopathological types of BCC are nodular, superficial, morphe form and infiltrative.[1] mBCC presents as skin-coloured slightly elevated or depressed area of induration with ill-defined borders. It is usually aggressive in behavior and can cause extensive local destruction. It needs to be differentiated from desmoplastic trichoepithelioma (DTE) and microcystic adnexal carcinoma (MAC).[2] DTE originate from follicular germinative cells and present as annular lesion with central depression and telangiectasia in young patients. BCC usually affects sunexposed sites like face and affects older age group. It may present with a large lesion while trichoepitheliomas are usually smaller in size (2-8 mm).[3] Both trichoepithelioma and BCC have nests of basaloid cells with follicular differentiation. Histopathological differences between them are shown in Table 1.[3] In our case, patient was younger and calcification and keratin cysts was a prominent finding on histopathology which created confusion with DTE. MAC are locally aggressive tumors that clinically present as skin colored facial lesions, invade deeper till subcutis, have perineural invasion and show ductal differentiation.[4]

Table 1

Histopathological differences morpheform BCC and Desmoplastic trichoepithelioma[3]

Feature	Morpheform BCC	Desmoplastic trichoepithelioma
High grade atypia	Present	Absent
Pleomorphism	Present	Absent
Mitotic figure	Common	Very rare, few
Nests of basaloid cells	May connect with epidermis	Usually don’t interact with epidermis
Myxoid stroma	Present	Absent
Fibroblastic stroma	Absent	Present
Horn cysts	Not usually seen	Usually seen
Small strands of epithelial elements	Less frequent	Frequent
Calcification	Uncommon	Common
Follicular, sebaceous, infundibular differentiation	Uncommon	Common
Retraction artifact	Often	Rare
Peripheral palisading of basaloid cells	present	absent
Cell necrosis	present	absent
Epidermal ulceration	present	absent
Papillary mesenchymal bodies	Less common	common
CK 20	Negative	Strongly positive
Androgen receptor	Frequently positive	Rarely positive
Bcl-2	Diffuse expression	Peripheral epithelial expression
CD 10	Stains normal and tumor cells	Stains stromal cells, especially around the tumor cells
CD 34	No expression	Stains fibroblastic stroma around basaloid cells

Dermoscopy of pigmented and nodular BCC is well described in literature while data on dermoscopy of mBCC is scarce particularly for dark skin individuals. In a systematic review, structureless hypopigmentation was seen in 75% of mBCC. Other features were arborizing vessel (51%), ulceration (58%) and large blue-grey ovoid nests (13%).[1]

Dermoscopy of DTE can also show ivory white background with keratin cysts, chrysalis like structures and arborizing vessels.[2] Ivory white background reflects sclerotic stroma in dermis. A recent case series found circular white structures in DTE and microcystic adnexal carcinoma.[5] These structures represented calcification and keratin cysts within the tumor. However, mBCC can also have calcification and keratin cysts rarely and hence dermoscopy alone cannot differentiate DTE, mBCC, and microcystic adnexal carcinoma. Therefore, adequate tissue sampling and immunohistochemistry must be performed in these cases for correct diagnoses and treatment.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Table 2

Neem in dermatology: Potential areas for further research[7,16–33]

Onychotillomania (due to bitter taste)

Insect repellent, myiasis*, pediculocidal, scabicidal**, tungiasis***

Antifungal (eg. dermatophytes, Candida albicans, Aspergillus spp.), antibacterial, antiviral (eg. herpes simplex virus-1 and coxsackie B4 virus), antimalarial, antileishmanial (Leishmania donovani)

Immunomodulatory

Wound-healing

Psoriasis

Anti-inflammatory, antioxidant, analgesic, antipyretic, antiarthritic, antifibrotic

Anti-cancer

Melanogenesis inhibiting activity, protection against UV-B damage

Anti-androgenic, antifertility, spermicidial

*A combination of neem and Hypericum perforatum oil in myiasis of domestic animals. **A combination of neem and turmeric was used in scabies. ***A combination of neem oil and coconut oil was used in tungiasis