When A Patient Has An Unusual Growth On A Toe

Joel Morse, DPM

A Guide To The Differential Diagnosis

The differential diagnosis of acquired periungual fibrokeratoma includes a variety of the following conditions.
Warts. Warts are very common small tumors of the skin caused by the human papillomavirus. A wart is usually a papillary growth that is slightly raised above the skin surface. One will usually find periungual warts under the nail plate or on the side. They are difficult to treat. There is also a cauliflower-like appearance. In this patient, the soft tissue growth was on top of the nail so this diagnosis was not as likely.
Osteochondroma. This is a benign tumor that contains both bone and cartilage, and usually occurs near the end of a long bone. This tumor is one of the more common benign bone tumors and has a cartilage-capped bony spur. The skin may be irritated on the surface, resulting in bursa formation. No bony component was visible on our radiograph.
Subungual exostosis. A subungual exostosis is an acquired, benign bony tumor that presents as a distal, subungual mass on the toe. It begins as a reactive fibrous growth that develops cartilage and ultimately ossifies. Complete excision remains the treatment of choice. In regard to the patient in this case, there was no obvious bony component on the radiograph.
Periungual fibromas. These are pink, smooth, fibrotic multilobulated nodules that occur around the nail folds and mainly in cases of tuberous sclerosis.7 They are flesh-colored papules that may displace and distort the nail bed. These periungual papules appear in late childhood and may be the sole cutaneous finding in some affected individuals.5,8
The periungual fibromas in tuberous sclerosis are also known as Koenen tumors.
Tuberous sclerosis is a multi-system genetic condition with key features including multiple facial angiofibromas, hypopigmented macules, seizures, cardiac rhabdomyoma and renal lesions. Tuberous sclerosis is the most common neurocutaneous syndrome after neurofibromatosis.9 Dermatologic manifestations may be the only clues to the diagnosis of the disorder, which is also marked by childhood seizures and mental retardation. Characteristic signs of tuberous sclerosis vary widely in severity and can also include hypopigmented “ash leaf spots,” fibrous plaques on the forehead, angiofibromas on the face (adenoma sebaceum), and a shagreen patch on the lower back. In this case, the patient was an adult with no history of seizures or other systemic issues.
Squamous cell carcinoma. This is a common malignant tumor arising from the keratinocytes of the epidermis. The most common clinical picture is a rapidly growing nodule that develops a central ulcer. It can also be a small, slightly raised warty or brownish nodule with hyperkeratosis. It is not commonly found on the foot. However, when any growth appears unusual, one should obtain a biopsy. Squamous cell carcinoma is the most common skin cancer among African-Americans and one study found that 65 percent of these carcinomas occurred in non-sun exposed areas. When it comes to Caucasians, the majority of squamous cell carcinomas are found in sun-exposed areas.10 Squamous cell carcinoma may also be confused with the diagnosis of a “recalcitrant” wart so getting a biopsy is very important.
Aggressive digital papillary adenocarcinoma. Such tumors are rare and arise from skin sweat glands. They usually involve solitary cystic nodules of less than 2 cm. Pain is a frequent presenting complaint. Clinically, these tumors tend to present as solid masses usually on the fingers, toes or adjacent parts of the palms and soles. There is a high rate of local recurrence and these tumors can metastasize.11
In the patient’s case, the periungual fibrokeratoma was not painful and more importantly, the biopsy ruled out an aggressive digital papillary adenocarcinoma.

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