Referred by her primary care provider, a 63-year-old woman presents to dermatology for evaluation of an asymp­tomatic lesion on her thumb. The lesion has slowly grown over a period of years and has persisted despite attempted treatment with topical steroid creams, antifungal cream, and cryotherapy. She denies any other similar occurrences or indeed any skin problems in general.

She has a dense medical history, mostly revolving around a heart transplant several years ago that necessitated ongoing immune suppression. This apparently played a role in the development of two squamous cell carcinomas (one on the face, the other on an arm), both successfully dealt with surgically. She admits that as a teenager she tanned and sunburned repeatedly. She specifically denies having diabetes.

On examination, the lesion proves to be a reddish brown, roughly ovoid plaque measuring about 3 x 2 cm, located on the medial right thumb. Its surface is smooth and nontender to touch, with no focal papularity and no scaling.

Given the failure of previous treatments and the patient’s immunosuppressed state, the decision is made to perform punch biopsy on the site. Care is taken to avoid the neurovascular bundle on the mid-lateral aspect of the digit, and the 3-mm defect is closed with a single nylon suture. The pathology report shows foci of degenerative collagen associated with palisaded granulomatous inflammation.

ANSWER
The correct answer is basal cell carcinoma (choice “d”), which only rarely affects the hands; it is far more common on more directly sun-exposed skin (eg, face, neck, and back).

Immunosuppressed individuals are at increased risk for squamous cell carcinoma (SCC; choice “a”), particularly those cancers associated with the human papillomavirus. These can present as odd plaques on the hands, so SCC belongs in the differential.

Mycobacterial infection (choice “b”) will demonstrate caseating (necrotic) granulomas and positive stains for acid-fast bacilli such as M marinum or M fortuitum; however, it can manifest with plaques.

Sarcoid (choice “c”) can be lesional and is thought to represent a reaction to an unknown antigen. Often reddish brown in color with plaquish morphology, sarcoid also demonstrates granulomatous changes microscopically; however, these are noncaseating epithelioid granulomas with no palisading.

DISCUSSION
Since granuloma annulare (GA) is notorious for appearing as papules and plaques on the extremities of females, this diagnosis was not a surprise. Often, GA is so obvious that a biopsy is unnecessary. However, given the patient’s immunosuppressed state and the many serious diagnostic possibilities to be ruled out (cancer was a possibility, and had the lesion represented sarcoidosis, it could have been the tip of a serious iceberg involving the liver, lung, or even heart), biopsy was the only option. As is often the case, thought was given to the site selected, in order to avoid damage to local structures or the creation of nonhealing wounds.

GA can occur in several forms, this patient’s case representing the most common one. It can also present as a generalized eruption, in a subcutaneous form, or even with blistering. At one time, it was thought that having GA meant that the patient had or was about to develop diabetes, but that assertion has long since been disproven.

Once diagnosed, GA does not really require treatment since it is self-limiting. However, treatment choices for this form include class 2 steroid creams or liquid nitrogen. This patient opted to do nothing, but she was very relieved to have ruled out more serious disease.