A 72-year-old female Indian patient presented with a right labial hyperpigmented plaque, which was intensely pruritic after urination. The plaque initially appeared as a small papule and grew to approximately 2 cm over the course of 2 months (Fig. 1). No other vulvovaginal abnormalities were present. The patient was also diagnosed with lichen simplex chronicus on the left side of the neck, which was well controlled with moisturizer and betamethasone dipropionate 0.05%. No oral lesions were present. She had undergone hysterectomy due to uterine fibroids. However, there was no history of immunosuppressive or radiation therapy. The patient also denied any ultraviolet exposure to the area. A strong family history of colon cancer was significant in her siblings. The skin biopsy from the vulvar lesion showed irregular basaloid lobules forming bulb-like structures with increased melanocytes, as well as abundant melanophages within a loose mucinous stroma. Immunoperoxidase stains indicated that the tumor was strongly positive for BerEP4, CK7, CK17, CAM5.2, and CK5 and 6.
Basal cell carcinoma (BCC) is the most prevalent cutaneous neoplasm, but its presence in non-sun-exposed areas of the body is extremely rare. Gibson and Ahmed (2001) have shown that in contrast with Caucasians, who have a high rate of skin cancer, these tumors comprise only 4% to 5% of all neoplasms in Hispanics and only 1% to 2% in black people. In a study of 18,943 BCCs, only 0.2% were located in the genital area (Gibson and Ahmed, 2001). In a study by Park et al. (2011), the most common histopathologic subtype of BCC in the genitalia is the nodular type, followed by the pigmented type. Although exposure to radiation, coal tar, and arsenic is a possible cause of BCC development in covered areas, alterations in immune surveillance in chronic dermatologic conditions, such as dermatitis, might be another explanation.