Squamous cell carcinoma is a common tumor. The association of squamous cell carcinoma with chronic draining osteomyelitis is known in general orthopaedic practice.1,14 Despite the frequency of hyperkeratotic lesions in relation to pressure points, squamous cell carcinoma is rarely diagnosed in the foot. Squamous cell carcinoma arises from keratinocytes of the epidermis. The malignant cells show different levels of keratin formation. This excess of keratin production may mimic a verruca or plantar keratosis.
Two cases of squamous cell carcinoma arising in common foot lesions are presented to draw attention to the potential for malignant transformation of chronic foot ulcers.
Case 1: Squamous Cell Carcinoma
A 64-year-old man reported a painful left foot. He had a callous beneath the second metatarsal head since the age of 19 years.
Physical examination revealed a prominent lesion on the plantar aspect of the left second metatarsal head. Radiographs demonstrated no bony lesions.
On June 16, 1994, he underwent debridement of his plantar callous with an osteotomy of the second metatarsal to relieve the pressure. The pathology report revealed verruca plantaris.
Two months later the patient had recurrence of a 2-cm ulcerative lesion on the plantar aspect of the foot; the lesion was slow to heal. No lymphadenopathy was noted. Debridement revealed squamous cell carcinoma.
In August 1994, he underwent repeat wide excisional biopsy of the left second metatarsal area. The pathology report noted a Grade 1 invasive keratinizing squamous cell carcinoma, 2.2 cm in its greatest dimension, which extended to within 1 mm of the margin of resection. A second metatarsal ray amputation was done in February 1995. The final pathology report showed no residual malignancy. The patient has only minimal pain and has returned to his previous level of activity (Figs 1, 2).
Case 2: Carcinoma Cuniculatum
A 12-year-old boy was seen in the general surgery clinic because of a painful plantar wart. He underwent excision of a plantar wart over the third, fourth, and fifth metatarsal heads in October 1993.
He was sent to the dermatology clinic because of a nonhealing ulcerative wound. A shave biopsy was performed on July 22, 1994, after failed treatment with topical Bleomycin chemotherapy. Clinically, he had a verrucous lesion measuring 2.5 × 0.5 cm. This sessile, bulbous lesion was indicative of a carcinoma cuniculatum. The patient was referred to the orthopaedic surgery clinic because of the size of the nonhealing, painful lesion.
A bone scan was performed that was consistent with cellulitis without bony involvement. A magnetic resonance imaging scan revealed a poorly circumscribed soft tissue mass.
In November 1994, an initially wide local excision of the lesion with amputation of third, fourth, and fifth metatarsals was performed. Intraoperative frozen sections confirmed squamous cell carcinoma but without clear margins. A Chopart's amputation was performed with tenodesis of tibialis anterior to the talus. The pathology report showed a 3 × 3 × 2 cm infiltrating well differentiated keratinizing squamous cell carcinoma. The patient has good movement of the ankle and minimal pain with ambulation.
Squamous cell carcinoma usually arises on sun exposed skin.2,10 Sun induced skin changes include elastic degeneration of the dermis, actinic keratosis, irregular pigmentation, and telangiectasis. Squamous cell carcinoma developing after chronic sun exposure has a fairly benign behavior: metastasic lesions develop in fewer than 2% of cases. However, squamous cell carcinoma also can arise from longstanding chronic granulomas, leukoplakia, actinic keratosis, and cutaneous horns. The association of malignant changes with chronic irritation of the skin surrounding a sinus tract because of osteomyelitis is well known.1,14 In this report, it was found that squamous cell carcinoma can arise from benign keratotic lesions on the foot. Levene found that of 511 skin tumors of the foot, 13% were squamous cell carcinoma.7 Half of these appeared on the plantar surface, predominantly on the metatarsal head and heel regions. These tumors arising on skin, not damaged by the sun, tend to be more aggressive and metastasize in 20% to 50%.9 Men are affected more often than are women (ratio: 3 to 1). The tumors usually occur in individuals 50 to 60 years of age.3 There almost always is induration of the skin around the lesion. If induration occurs in a preexisting lesion, malignancy can be suspected.
Squamous cell carcinoma of the foot may be papillary12,13 or ulcerative.6 Squamous cell carcinoma initially may be mistaken for an atypical verruca or plantar keratosis. Warty lesions such as viral warts or keratoses are not indurated, and viral warts often are multiple. There is a well defined subtype of squamous cell carcinoma called epithelioma cuniculatum.4,5,8,11 This always occurs on the sole of the foot. It is well differentiated and has a typical presentation. There is a bulbous mass with multiple sinuses from which a greasy, foul-smelling material can be expelled. In untreated cases, squamous cell carcinoma usually spreads to regional lymph nodes.10
In squamous cell carcinoma, the cells often appear as well differentiated keratinocytes. These are polygonal cells with abundant cytoplasm. Parakeratotic horny pearls and individually keratinized cells may be present. Sometimes the cells are anaplastic with basophilic cytoplasm, which are almost impossible to trace to their origin.
There is invasion of the dermis through the basement membrane. This causes an inflammatory reaction in the dermis. If the basement membrane remains intact, the lesion is a carcinoma in situ and is called Bowen's disease.
Incision biopsy should be undertaken if there is any indication of malignancy. A shave biopsy is inadequate. These lesions are on the plantar surface of the foot, so longitudinal incisions can prevent painful scars and permit regional excision of the lesion. Local destruction by curettage and cauterization or by cryotherapy sometimes is advocated in dermatologic literature. However, it is difficult to establish a safe margin. Radiotherapy often leaves fragile scars and may be followed by a radionecrosis. Excision margins of at least 3 to 5 mm should be obtained beyond the palpable induration. Metatarsal ray amputation is a useful procedure for forefoot lesions. If recurrence or inadequate margins are obtained, a more proximal amputation is necessary.
Orthopaedic surgeons have long been aware of squamous cell carcinoma developing from chronically inflamed sinus tracts in osteomyelitis. However, this report focuses on the development of squamous cell carcinoma in what initially appeared to be an innocuous plantar keratosis and a verrucous lesion. If it is a single indurated lesion with an ulcer, one should be suspicious. An incision biopsy should be performed. If this confirms the diagnosis, wide excision with a safe margin should be performed. With recurrence, a functional amputation should be performed.
1. Fitzgerald RH, Brewer NS, Dahlin DC: Squamous cell carcinoma complicating chronic osteomyelitis. J Bone Joint Surg 58A:1146-1148, 1976.
2. Galinski AW, Williams JE, Geduldig SB: Squamous cell carcinoma: A review of the literature and case report. J Am Podiatr Assoc 71:P505-508, 1981.
3. Glass AG, Hoover RN: The emerging epidemic of melanoma and squamous cell cancer. JAMA 262:2097-2100, 1989.
4. Horn L, Sage R: Verrucous squamous cell carcinoma of the foot: A report of five cases. J Am Podiat Med Assoc 78:227-232, 1988.
5. Kao GF, Graham JH, Helwig EB: Carcinoma cuniculatum (verrucous carcinoma of the skin): Clinicopathologic study of 46 cases with ultrastructural observations. Cancer 49:2395-2403, 1982.
6. Kouskoukis CE: Stump of the experts. J Dermatol Surg Oncol 10:599-643, 1984.
7. Levene M: Distribution of skin tumors of the sole of the foot. Br Med J 1:1519-1520, 1958.
8. Neufeld RI, Kurtzer CM, Estersohn HS, Napoli JD: Verrucous squamous cell carcinoma of the foot: A rare case history. J Am Podiatr Med Assoc 75:300-305, 1985.
9. Murphy GF, Kwan TH, Mihm MC: The Skin. In Robbins SL, Cotran RS, Kumar V (eds). Pathologic Basis of Disease. Ed 3. Philadelphia. WB Saunders 1266-1267, 1984.
10. MacKie RM: Epidermal Skin Tumors. In Rook A, Wilkinson DS, Ebling FJG (eds). Textbook of Dermatology. Ed 5. Boston, Blackwell Scientific, 1497-1502, 1992.
11. Smith PJ, Hylinski JH, Axe S: Verrucous carcinoma: Epithelioma cuniculatum plantare. J Foot Surg 31:324-328, 1992.
12. Spinosa FA: Squamous cell carcinoma of the plantar aspect of the foot. J Foot Surg 26:253-255, 1987.
13. Steinhart AN: Squamous cell carcinoma of the sole: Case presentation and review of the literature. J Am Podiatr Assoc 70:330-332, 1980.
14. Wu KK: Squamous cell carcinoma arising from a chronic osteomyelitis of the ankle region. J Foot Surg 29:608-612, 1990.