Subcutaneous Verrucous Carcinoma of the Plantar Calcaneus
Verrucous carcinoma (VC) is a rare diagnosis, and even more rare when it arises in the deep tissues of the foot. When VC arises in the epidermis and dermis, it is often also referred to as epithelioma cuniculatum. VC is a type of squamous cell carcinoma and can occur in any area of the skin or mucosa.1 Although it has low metastatic potential, VC can have adverse effects on surrounding tissues, and thus one should treat it with wide excision or amputation if VC threatens to involve proximal or deeper structures.2 Temple and colleagues noted that due to the frequency of benign lesions in the foot, VC being one of them, potential malignancies often go improperly treated initially.3
Clinical and histopathological features of VC include an average patient age of 63.6 years, occurring more often in males.1,4 Most cases are in the foot, followed by the lower legs. Histologically, VC exhibits an exo-endophytic growth pattern with severe keratinization and a blunted rete ridge with pushing margins. When it comes to malignant tumors of the foot and ankle, prompt identification, diagnosis, and referral to the appropriate specialist are vital in the treatment of the patient.
Even with appropriate treatment, a recent review demonstrated recurrence rates as high as 75%.5 They further outlined a more common occurrence of VC in those in the sixth and seventh decades of life, and those with HPV types 11, 16, 18, and 33. In some cases, with deeper involvement into adjacent structures, where excision would cause functional loss, an amputation may become warranted. Prince and colleagues also conducted a study investigating the prognostic factors influencing recurrence.6 They found higher recurrence rates in the nonglabrous skin of the foot and great toe. The authors found that if the tumor did recur, then it was only present locally and did not tend to metastasize or progress to traditional squamous cell carcinoma.
Ogunlana and team published a case wherein recurrence caused a repeat operation.7 The patient had initial amputation of the hallux with wide excision. However, further spread of the lesion was to the lesser digits postoperatively and the patient eventually went on to transmetatarsal amputation.
A Closer Look at the Removal of the Mass
A 63-year-old male presented with uncontrolled diabetes with a greater than 1-year history of a small plantar medial heel wound. The patient had local wound care and debridement routinely without significant improvement. The patient did have a skin biopsy by an outside provider approximately 1 year earlier, which returned as “wound tissue,” without any evidence of atypical cells or verruca. The patient had no evidence of bony changes on radiographs, or clinical abnormality suggesting alternate diagnosis to chronic diabetic wound. Due to the lack of clinical improvement of the wound, the patient was agreeable to surgical debridement, resection, and delayed closure. This patient presented to a surgery center in July 2020 for surgical excision of a plantar medial heel wound with primary closure.
The original plantar medial heel wound measured approximately 3mm in diameter with extension into the deep soft tissues prior to intervention. We placed 2 semi-elliptical converging incisions about the wound and excised the skin (Figure 1). Upon further examination of the surgical wound, there was a well-defined soft tissue mass present within the plantar calcaneal fat pad in the subcutaneous tissue. The abnormal appearing mass was located extending from the wound base and traveled laterally along the plantar aspect of the foot in close apposition to the plantar fascia. The soft tissue mass appeared to have its own blood supply and was fully encapsulated and spongy in nature. We used sharp and blunt dissection to carefully dissect around the soft tissue mass along the plantar aspect of the right heel, taking care to leave only normal-appearing tissue in the deep layers of the plantar foot. Once the soft tissue mass had been fully dissected and no further abnormal tissue was visible, we completely removed the soft tissue mass from the plantar aspect of the right heel and (Figures 2-3) sent this labeled mass to pathology. At this time we also took a bone biopsy from the calcaneus.
Biopsy Results and the Postop Course
The pathology report revealed a “4.1 x 3.0 x 2.1 cm irregular shaped lobulated tan-pink soft tissue containing atypical squamous hyperplasia suggestive of verrucous carcinoma.” We were not able to obtain a histological slide exam for the patient; however, features of deep portion of this type of soft tissue tumor include well differentiated squamous nests, some with keratotic centers surrounded by dense inflammation.8 The bone biopsy taken during surgery was negative for any signs of osteomyelitis at that time.
The patient was inconsistent with postoperative follow-up. The patient got referrals to dermatology as well as oncology. Chart review detailed several attempts by both specialties to contact the patient for evaluation and treatment, but the patient failed to respond or follow up. The patient ultimately returned to the surgeon’s clinic several months later with a dehisced wound with calcaneal bone exposed. We performed repeat incision and drainage, bone biopsy, and advanced imaging at that time, which revealed extensive diffuse osteomyelitis to the calcaneus. After discussing options with the patient, the patient ultimately decided to undergo below-knee amputation.
What You Should Know About Verrucous Carcinoma
Due to the rare nature of VC, there are no high-level studies available. Most of the research involves case series or case reports. A literature review indicates very few reported cases of VC of the foot, with even fewer located in the deep tissues. The verrucous carcinoma presented in this case report is even more unique as it was located deep to the epidermis and dermis, in the subcutaneous tissue of the plantar heel.
Several studies have noted VC in the dermal and epidermal layers of the foot and ankle. Di Palma presented a similar case of bilateral VC in a patient with chronic diabetic ulcers, which also delayed the diagnosis.9 They stress the importance of high index of suspicion for chronic non-healing wounds in the diabetic foot.
Similar to the case presented in this report, Pempinello identified a case of verrucous carcinoma that invaded the adjacent bony structures of the foot and ankle, which required below-knee amputation.10
Unfortunately, the patient in our case developed diffuse osteomyelitis of the calcaneus in the affected limb due to non-adherence and underwent a below knee amputation. Treatment of choice for VC is routinely a wide excision rather than amputation. However, the resultant wound and osteomyelitis complicating the postoperative site, rather than the VC directly, ultimately guided treatment towards a permanent proximal procedure. High suspicion and attentiveness to detail in these cases provide the best chance for VC to successfully be treated with a single, initial operation. Although slow growing, verrucous carcinoma is a malignant soft tissue tumor and one must handle it with care and treat promptly to prevent further spread.
Jay Badell, DPM, MS, FACFAS is a fellowship trained foot and ankle surgeon in Greenfield, IN.
Clinton Heyer, DPM is a foot and ankle surgeon in Indianapolis, IN.
Tracy Lee, DPM, is a foot and ankle surgeon in Indianapolis, IN.
References
1. Miller SB, Brandes BA, Mahmarian RR, Durham JR. Verrucous carcinoma of the foot: a review and report of two cases. J Foot Ankle Surg. 2001 Jul-Aug;40(4):225-31.
2. Gordon DK, Ponder EN, Berrey BH, Kubik MJ, Sindone J. Verrucous carcinoma of the foot, not your typical plantar wart: a case study. Foot (Edinb). 2014 Jun;24(2):94-8.
3. Temple HT, Worman DS, Mnaymneh WA. Cancer Control. 2001; 8(3):262-268.
4. Schwartz RA. Verrucous carcinoma of the skin and mucosa [published correction appears in J Am Acad Dermatol 1995 May;32(5 Pt 1):710]. J Am Acad Dermatol. 1995;32(1):1-24. doi:10.1016/0190-9622(95)90177-9
5. Fawaz B, Vieira C, Decker A, Lawrence N. Surgical treatment of verrucous carcinoma: a review. J Dermatolog Treat. 2022 Jun;33(4):1811-1815.
6. Prince ADP, Harms PW, Harms KL, Kozlow JH. Verrucous carcinoma of the foot: a retrospective study of 19 cases and analysis of prognostic factors influencing recurrence. Cutis. 2022 Mar;109(3):E21-E28.
7. Ogunlana O, Panchbhavi VK, Norbury WB, Raji M. Squamous cell carcinoma of the foot occurring in a wart. Foot Ankle Spec. 2022 Jan 12:19386400211070431.
8. Ireland A, Ardakani NM. Verrucous carcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumornonmelanocyticverrucousscc.html. Accessed Aug. 8, 2023.
9. Di Palma V, Stone JP, Schell A, Dawes JC. Mistaken diabetic ulcers: a case of bilateral foot verrucous carcinoma [published correction appears in Case Rep Dermatol Med. 2018 Apr 15;2018:6405129. doi: 10.1155/2018/6405129]. Case Rep Dermatol Med. 2018;2018:4192657. Published 2018 Jan 23. doi:10.1155/2018/4192657
10. Pempinello C, Bova A, Pempinello R, Luise R, Iannaci G. Verrucous carcinoma of the foot with bone invasion: a case report. Case Rep Oncol Med. 2013;2013:135307. doi:10.1155/2013/135307
11. Ye Q, Hu L, Jia M, Deng LJ, Fang S. Cutaneous verrucous carcinoma: A clinicopathological study of 21 cases with long-term clinical follow-up. Front Oncol. 2022 Oct 13;12:953932. doi:10.3389/fonc.2022.953932.
