Giant cutaneous squamous cell carcinoma of the scalp arising in the setting of folliculitis decalvans

Background

Skin cancer is the most common malignancy in the United States and accounts for 40% of all cancers in Caucasians and 1%–5% in people of colour.1 More specifically, skin cancer accounts for 1%–2% of all cancers in African Americans (AAs).2 Among all skin cancers, squamous cell carcinoma (SCC) is the most common skin cancer in AAs, with an incidence of approximately 3 per 100 000, and the second most common type in Caucasians, Hispanics and Asians.2 Overall, SCC accounts for about 75% of all deaths caused by non-melanoma skin cancers in the general population.3 SCC primarily affects older patients, typically over the age of 50. The incidence of SCC in patients younger than 40 years is 3.9 per 100 000.4 In Caucasians, SCC usually develops in sun-exposed areas, while in AAs, SCC often develops in sun-protected areas such as the lower limbs and anogenital region.2 It is well known that ultraviolet (UV)-radiation-induced mutations in N-RAS and p53-related genes play a central role in the pathogenesis of SCC in light-complexioned skin.5 The increased epidermal melanin in dark skin protects from chronic UV radiation, resulting in a low incidence of SCC in AAs. Chronic inflammation and scaring are more significant risk factors for SCC in dark skin.6 SCCs larger than 10 cm in all races are rare, and few cases have been reported. Due to the low incidence, published data of SCC, especially giant SCC, in the AA population is minimal.

Case presentation

We report an AA man in his 40s who presented with a giant SCC (greater than 10 cm). He had a long-standing history of folliculitis decalvans (chronic cicatricial alopecia), clinically presenting as atrophic hyperpigmented plaques on the scalp. No medical history or family history of neoplasm was reported. Previously, the patient noted enlargement of plaques on the right posterior scalp that grew into cutaneous horns with occasional itching. He visited the dermatologist, and a shave biopsy showed skin with extensive dermal scarring, mixed inflammation, follicular plugging and rupture, extravasated hair shafts, and features consistent with folliculitis decalvans. A punch biopsy was performed in the following years, and showed histology similar to the previous shave biopsy. Special stains were negative for microorganisms, including spirochetes. Several months prior to his diagnosis of SCC, the patient noted that the cutaneous horns on his scalp grew into an 11 × 10 × 5 cm exophytic, verrucous-like mass.

Investigations

A skin biopsy of the new mass showed features of pseudoepitheliomatous hyperplasia with severe inflammation and some concerning cytological atypia and architectural complexity. Based on the biopsy, confident exclusion of a heavily inflamed carcinoma was not possible. A concurrent microbiology analysis of the scalp revealed heavy growth of Pseudomonas aeruginosa.

Since the skin biopsies were inconclusive, the patient was scheduled for surgical resection of the lesion. A preoperative head CT scan demonstrated a bulky soft tissue mass extending across the midline, the left parietal scalp and the right posterior subgaleal soft tissue. No distinct areas of osseous erosion or destruction are present (figure 1A,B). The patient underwent mass resection with minimal 2 cm negative margins confirmed by frozen sections.

The oriented specimen was received fresh, and as shown in figure 1C, revealing a tan, firm, exophytic mass with a lobulated surface. Serial sectioning of the mass revealed invasion of the subcutaneous tissue and negative margins (figure 1D,E). The histological evaluation showed moderately differentiated keratinising SCC with clear cell changes in a background of severe acute and chronic inflammation (figure 2A,B), folliculitis (figure 2C) and scarring alopecia (figure 2D). The tumour was measured to be 4.1 cm with subcutaneous invasion but lymphovascular invasion noted.

Differential diagnosis

The differential diagnosis was primarily between SCC and pseudoepitheliomatous hyperplasia. Pseudoepitheliomatous hyperplasia can occur secondary to underlying infection or another tumour type (lymphoma, granular cell tumour, etc).

Treatment

The patient received reconstruction of his scalp defect with a right anterolateral thigh free flap. Given the size of the defect after resection, this was the only reconstructive option that was suitable. The postoperative course was notable for a haematoma, which was evacuated promptly, but was otherwise uneventful. The patient was ultimately discharged 2 weeks after his initial surgery. He did not receive any adjuvant therapies, as these were not warranted.

Outcome and follow-up

The patient was followed up by the head and neck surgery department. He cleaned the surgical wound at home and received oral antibiotics. The wound healed well, and the patient had no specific complaints. However, occipital lymphadenopathy was noted during a follow-up visit 4 months after surgery. A CT shows an enlarged lymph node. The lymph node’s fine needle aspiration and subsequent cytological evaluation revealed metastatic SCC (figure 3).