Two cases of perianal basal cell carcinoma

A 71-year-old female presented with a perianal mass seen for the past 10 years, growing slowly over 12 months prior to presentation. Her past medical history included primary biliary cirrhosis, dyslipidemia, gastroesophageal reflux disease, and osteoporosis. A dermatological examination revealed a reddish exophytic nodular lesion approx. 30 × 25 mm in size in the perianal region at the 9 o’clock position (Fig. 1a). Aside from the perianal lesion, the anal canal was normal. A biopsy of the perianal region was performed, since the preliminary diagnosis was skin cancer, as squamous cell carcinoma or melanoma. The tumor was composed of a proliferation of basaloid cells with peripheral palisading in the dermis, and a mild mucin deposition was noted around the tumor (Figs. 1b–1d). Histological findings revealed superficial basal cell carcinoma (BCC). The patient was referred to another hospital for further treatment.


CASE 1
A 71-year-old female presented with a perianal mass seen for the past 10 years, growing slowly over 12 months prior to presentation. Her past medical history included primary biliary cirrhosis, dyslipidemia, gastroesophageal reflux disease, and osteoporosis. A dermatological examination revealed a reddish exophytic nodular lesion approx. 30 × 25 mm in size in the perianal region at the 9 o'clock position (Fig.  1a). Aside from the perianal lesion, the anal canal was normal. A biopsy of the perianal region was performed, since the preliminary diagnosis was skin cancer, as squamous cell carcinoma or melanoma. The tumor was composed of a proliferation of basaloid cells with peripheral palisading in the dermis, and a mild mucin deposition was noted around the tumor (Figs. 1b-1d). Histological findings revealed superficial basal cell carcinoma (BCC). The patient was referred to another hospital for further treatment.

CASE 2
An 80-year-old female presented with an itchy brownish lesion on the right side of the perianal region seen for the past year. She had a history of angina pectoris, uterine fibroid, and uterine prolapse. There was no medical history of radiotherapy, chemical exposure, or trauma to the genital area. There was no remarkable family history of skin disease or skin cancer. A physical examination revealed a single brownish patch with slight itching near the anus (Fig. 2a). Dermatoscopy showed a large bluish-gray ovoid nest, multiple bluishgray globules, and arborizing vessels (Fig. 2b). An incision biopsy was performed, showing basaloid cells with peripheral palisading in the superficial area of the dermis (Fig. 2c). The tumor was excised completely with a 2-4 mm clear margin. After the excision, there was no evidence of recurrence during a 3-month followup period.
Chronic exposure to the sun is a significant predisposing factor for BCC. More than 80% of BCC cases occur on sun-exposed areas, such as the head and neck [1]. Consequently, BCC of areas that are not sun-exposed, such as the axilla, nipple, or the genital and perianal areas, are extremely rare. It is estimated that perianal BCC accounts for only 0.08% of all BCCs [2]. In Japan, Hamada investigated 412 cases of BCC, and only 2 (0.5%) perianal BCCs were identified. Nagamatsu reported 2 (2.4%) BCCs located in the preanal area out of the 83 studied.
These regions are usually well covered and not exposed to sunlight. The etiologic factors for perianal BCC have not yet been clearly defined but, according to previous reports, the possible causes include radiation therapy, alternation in immune surveillance, exposure to coal tar or arsenic, sexually transmitted diseases, burns, traumatic scars, and chronic skin irritation [3,4]. Neither of our two cases had any of these etiologies. BCC occurs mainly in middle-aged and elderly patients, but the average age is slightly higher for perianal BCC, compared to the other types of BCC [5]. Moreover, most patients are men, and lesions are usually less than 2 cm in diameter [6]. Case 1 presented with a large ulcerated nodule 30 × 25 mm in size. Case 2 presented with a hyperpigmented plaque with central ulceration. Our cases showed, thus, one nodular and one superficial BCC. A literature review revealed that the most common type of perianal BCC is nodular, followed by superficial [2].
According to the National Comprehensive Cancer Network (NCCN), a BCC in the perianal region is considered high-risk. Treatment options for   perianal BCC include wide local excision and Mohs micrographic surgery. Case 2 was treated with a 2-4 mm excision with a clear margin, and no recurrence was observed during a 3-month follow-up period. A standard 4 mm margin excision should be considered in select tumors. In summary, because perianal BCC is so uncommon and the lesions are located in an inconspicuous area, Aldana insists that a biopsy should be considered for suspicious lesions in the perianal and genital areas [7]. Increased awareness of perianal BCC may contribute to the prevention of delayed diagnosis.

Consent
The examination of the patient was conducted according to the principles of the Declaration of Helsinki.