Adenoid Basal Cell Carcinoma over the Scalp

Dear Editor,

A 25-year-old girl, a known case of Gorlin-Goltz syndrome, presented with a bluish-black nodule of around 7 mm in maximum diameter over the right frontoparietal scalp for the past 10–15 years [Figure 1a, b]. It was asymptomatic except for slight bleeding post trauma while combing her hair. She had multiple, superficial, flat basal cell carcinomas (BCCs) over the scalp as a part of Gorlin-Goltz syndrome. Dermoscopy of the nodule in a polarized mode showed diffuse blue-gray discoloration with areas of irregular white streaks and superficial white scales. Scaling was also noted over the surrounding scalp skin [Figure 2]. Based on the history and clinical evaluation, we kept the differential diagnoses of blue nevus and nodular melanoma. Excisional biopsy was performed to confirm the diagnosis which showed pathology composed of basaloid cells arranged in solid strands and reticulated pseudoglandular pattern with peripheral palisading, in a mucinous stroma of the dermis [Figure 3a, b]. A few islands of cells were connected to the overlying epidermis. The tumor was diffusely strongly immunoreactive for BerEP4 [Figure 4]. These findings were suggestive of adenoid basal cell carcinoma.

Figure 1.

(a and b) Bluish-black nodule over right frontoparietal scalp. Flat, hyperpigmented plaque of BCC is seen in the surrounding skin

Figure 2.

Diffuse blue-gray discoloration with areas of irregular white streaks and superficial white scales (using hand-held polarized dermatoscope IDS1100, ILLUCO, KOREA)

Figure 3.

(a) Basaloid cells arranged in solid strands and reticulated pseudoglandular pattern in a mucinous stroma of the dermis (H and E 10x). (b) Basaloid cells arranged in solid strands and reticulated pseudoglandular pattern in a mucinous stroma of the dermis (H and E 40x)

Figure 4.

Tumor was diffusely strongly immunoreactive for BerEP4 (10×)

BCC is the most common malignant tumor of the skin. Histological variants include nodular/nodulocystic, micronodular, infiltrative, sclerosing, keratotic, basosquamous, pigmented, superficial, ulcerative, clear cell, adenoid, signet ring cell, etc.[1] Adenoid is a rare histological variant of BCC with a reported incidence rate of 1.3% to 20.91%.[2,3,4] It is considered to be a rare subtype of nodular BCC and is considered a low-grade malignancy as compared to other variants of BCC. Adenoid BCC was found to have a higher recurrence rate than other low-risk BCCs based on a recent case–control study.[5] Clinically it can present as a pigmented or nonpigmented ulcer or a nodule without any site predilection. Histology of adenoid BCC is suggestive of a predominant adenoid pattern with the reticular arrangement of thin strands of basaloid cells, with tubules and few dilated spaces containing mucin. Peripheral palisading, retraction artifacts, and connection of tumor islands with the epidermis can be appreciated.[1] Histological differentials are adenoid cystic carcinoma, desmoplastic trichoepithelioma, and primary cutaneous cribriform apocrine carcinoma. Lack of epidermal connection and the presence of perineural invasion are seen in adenoid cystic carcinoma. The presence of large polygonal to round cells with abundant, granular, eosinophilic cytoplasm, and decapitation secretion, lack of peripheral palisading, no retraction artifacts, and no connection of tumor islands with the epidermis are the features of primary cutaneous cribriform apocrine carcinoma. BerEP4 positivity is seen in BCC and desmoplastic trichoepithelioma and immunostaining for S-100, epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA), and cytokeratin (CK-7) is positive in adenoid cystic carcinoma and cribriform apocrine carcinoma. The presence of keratinized horn cysts, fibrous stroma, calcification, positivity of CK 15, CK 20, pleckstrin homology-like domain family A member 1 (PHLDA 1), and absence of mitotic activity and pleomorphism differentiates desmoplastic trichoepithelioma from BCC.[6]

As seen in our case, the nodular lesion of adenoid BCC has also been reported by Saxena et al.[4] but dermoscopy findings were not mentioned. Although, dermoscopy features are quite characteristic in pigmented BCC cases, but in our patient, there was only diffuse blue-gray discoloration likely diffuse ovoid nests with only white streaks and no telangiectasias, maple-leaf structures, brown pigmentation, and ulcerations.[7] The dermoscopy features of adenoid BCC reported in the literature include a whitish veil, blue-gray areas, black dots, and globules, thin vessels by Akay and Erdem, and yellowish structure with polymorphic vascularization at the periphery and hemorrhagic suffusion by Senhaji et al.,[8,9] hence causing a diagnostic dilemma. This case highlights the importance of clinico-dermoscopic-histopathological correlation and the need for dermatologists to be aware of this uncommon variant of adenoid BCC and that the characteristic dermoscopy findings may not always be present.

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Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.