Postoperative electron beam irradiation to prevent recurrence of refractory subungual exostosis: a case report

Introduction

Nail abnormalities, including ingrown nails, are common. However, occasionally ingrown nails can be intractable. In these cases, chronic inflammation often leads to the development of hyper-granulation tissue; rarely, subungual exostosis may occur.

If subungual exostosis occurs, adequate excision of the lesion is required. However, extensive excision increases the risk of postoperative nail deformity (1,2), whereas inadequate excision increases the risk of recurrence. Although electron-beam irradiation has been used to prevent recurrence after surgical excision of heterotopic ossification (3,4), of which subungual exostosis is known to be a subtype according to the classification based on pathological aspects (5,6), no studies have reported the use of electron-beam irradiation after surgical excision of subungual exostosis.

Herein, we report a case wherein postoperative electron-beam irradiation was used to prevent recurrence of a refractory subungual exostosis caused by an ingrown nail. We hope that this report would help readers select an appropriate treatment of similar cases. We present this case in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-24-26/rc).

Case presentation

A 40-year-old woman with an ingrown right toenail was referred to our department. There was no relevant medical history. At the time of initial examination, the ingrown nail had been excised by the previous physician from the tip to the lateral nail fold, preserving the nail root and matrix; a large red raised lesion was located from the nail bed to the lateral nail fold (shown in Figure 1). Since excision of this lesion would result in a large skin defect, the patient underwent extraction of the root and matrix of the ingrown nail, excision of the raised lesion, nail matrix cauterization with phenol (three applications, 40 s each), and artificial dermal graft under local anesthesia. The raised lesion was firmer than the infected granulation tissue; curettage was performed on the cortex and medulla of distal phalanx.

Figure 1 Image taken at initial examination. A large raised red lesion is observed extending from the nail bed to the lateral nail fold.

Epithelialization was completed by 3 months postoperatively. However, 5 months after surgery, a large, hard, red, raised lesion similar to but larger than the lesion present at the initial visit was observed, and the nail was excluded (shown in Figure 2). Therefore, excision of this lesion and two-stage skin reconstruction was planned.

Figure 2 Image taken 5 months after initial surgery. A large red raised lesion similar to that observed initially recurs and compresses the nail.

Six and a half months after the initial surgery, marginal resection of the raised lesion to preserve the nail matrix and minimize nail bed loss was performed under local anesthesia. On visual examination, the resection site showed bone marrow exposure without obvious tumor remnants (shown in Figure 3). Histopathological examination led to a diagnosis of subungual exostosis (shown in Figure 4). Therefore, we considered the patient to have recurrent refractory subungual exostosis and planned electron-beam irradiation to prevent further recurrence.

Figure 3 Image taken after resection of the recurrent lesion.

Figure 4 Histopathological findings following hematoxylin and eosin staining. (A) Collagen fiber proliferation is observed in the reticular dermis, the skin is thin, and heterotopic ossification occupies most of the area. Magnification, ×4. (B) Cartilage formation is observed near the border. Magnification, ×100.

Two weeks after surgery, the exposed bone marrow was covered by granulation tissue with good blood flow; the patient was able to undergo skin grafting. One month postoperatively, debridement and full-layer skin grafting were performed, considering the risk of postoperative nail bed contracture resulting in nail deformity (shown in Figure 5A). Histopathological examination of the debrided tissues revealed no subungual exostosis. The skin grafts healed well, and electron-beam irradiation (4 doses of 5 Gy, every day for 4 days) was performed two and a half weeks after skin grafting (shown in Figure 5B). At a follow-up visit 2 months after skin grafting, some hypertrophic scarring was observed at the grafting site (shown in Figure 5C); a locally injected steroid (triamcinolone acetonide; KENACORT^®, Bristol Myers Squibb, New York, USA) was therefore administered three times in 6 months. One year and 7 months after the surgery, the nail condition was stable without recurrence of subungual exostosis, nail morphology was good, and there was almost no difference between the right and left nails (shown in Figure 5D). No further follow-up visits were deemed necessary.

Figure 5 Images taken after resection of recurrent subungual exostosis. (A) Four weeks after surgery, full-thickness skin grafting is performed. (B) Good graft healing is observed two and a half weeks after skin grafting. (C) Two months after skin grafting, some hypertrophic scarring is observed. (D) At the final follow-up, nail morphology is good, with almost no difference between the right and left nails.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

Subungual exostosis can be divided into osteochondroma and fibrous ossification types based on histopathology. Osteochondroma type manifests ossification under the vitreous cartilage cap. The fibrous ossification type, also called exostosis, is a direct ossification extending from fibrous cartilage or from fibrous tissue to bone. Ossification in patients with subungual exostoses is irregular, with a mixture of ossification of cartilage tissue and direct ossification of fibrous tissue (7). Subungual exostosis is known to be a subtype of heterotopic ossification according to the classification based on pathological aspects (5,6). The translocation t(X;6)(q22;q13–14) has been associated with subungual exostoses that occur secondary to inflammation, degeneration, trauma, or tumors (7,8). The main cause of subungual exostosis is mechanical or chronic irritation or trauma; it primarily occurs under the nail plate of the distal phalanx in young adults (6). In this case, we suggest that the subungual exostosis was triggered by chronic irritation and inflammation resulting from the ingrown nail. A histopathological diagnosis was made after the second excision, and since this lesion was similar in morphology to the initial lesion, we considered that the histopathological findings confirmed the subungual exostosis to be a recurrent lesion although the pathologic margins of the initial resection specimen were unknown.

Surgical excision is the first-line treatment of subungual exostosis. Completely removing the lesion is important, particularly the base, using a surgical technique that provides a clear operative field of vision (1,2). Since the margins of the lesion are often unclear, recurrence could occur, at a reported rate of approximately 10% (2,9). Use of the fish mouth technique is associated with inadequate resection with a resultant recurrence rate of 20% (10). Typically, if there are no signs of recurrence within 5 months after surgery, the patient is considered cured (2). Wide resections are more likely to result in a cure; however, removal of too much of the nail bed or removal of the nail matrix is associated with a high probability of postoperative nail deformity (1,2). In this case, we planned a marginal resection of the tumor for cosmetic reasons, a two-stage skin grafting procedure, and electron beam irradiation to prevent recurrence. Although electron-beam irradiation is sometimes used to prevent recurrence after heterotopic ossification excision (3,4), there have been no reports on electron-beam irradiation following surgical excision of subungual exostosis.

The recurrence rate after surgical resection of heterotopic ossification ranges between 5% and 15% (11,12); irradiation has been reported to show some efficacy in the prevention of recurrence. The Japanese Society for Radiation Oncology guidelines recommend 3–5 doses of electron-beam irradiation totaling approximately 8.0–12.0 Gy for the prevention of heterotopic ossification recurrence after surgical resection (3). Additionally, several reports have shown a significant reduction in the recurrence rate after postoperative irradiation (4,11,13). In the future, the dose needed to prevent recurrence of subungual exostosis should be discussed in further research. Furthermore, celecoxib may be used in addition to electron-beam irradiation for the prevention of postoperative recurrence of heterotopic ossification (12). Although the patient in our case did not opt for it, celecoxib may be useful for the prevention of postoperative recurrence of subungual exostoses.

Radiation-induced cancer is a potential late complication of electron-beam irradiation (14). The long interval between irradiation and cancer development makes the scale of the risk difficult to assess; this risk is further influenced by various factors such as irradiation site, age, and sex (14). Nevertheless, the risk is considered minimal in adults if electron-beam irradiation does not extend to the thyroid or mammary glands (14).

This study reported the successful treatment of a recurrent subungual exostosis by marginal resection of the lesion to preserve the nail matrix and nail bed for cosmetic reasons, followed by a two-stage skin grafting procedure and electron-beam irradiation. Subungual exostosis is a form of heterotopic ossification, and may be thereby susceptible to electron-beam irradiation. A future case series regarding postoperative electron-beam irradiation for subungual exostosis will extend these findings, as will a comparative study of cases of subungual exostosis treated with and without postoperative electron-beam irradiation.

Conclusions

We report a successfully treated case of a refractory subungual exostosis caused by an ingrown nail for which we performed a marginal resection of the lesion to preserve the nail matrix and nail bed as much possible, a two-stage skin grafting procedure, and postoperative electron-beam irradiation to prevent recurrence. Postoperative electron beam irradiation may contribute to the prevention of subungual exostosis recurrence, allowing marginal resection to be performed for achieving optimal cosmetic results.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-24-26/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-24-26/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-24-26/coif). N.I. serves as an unpaid editorial board member of AME Case Reports from December 2023 to November 2025. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Landon GC, Johnson KA, Dahlin DC. Subungual exostoses. J Bone Joint Surg Am 1979;61:256-9. [Crossref] [PubMed]
2. DaCambra MP, Gupta SK, Ferri-de-Barros F. Subungual exostosis of the toes: a systematic review. Clin Orthop Relat Res 2014;472:1251-9. [Crossref] [PubMed]
3. Micke O, Seegenschmiedt MHGerman Working Group on Radiotherapy in Germany. Consensus guidelines for radiation therapy of benign diseases: a multicenter approach in Germany. Int J Radiat Oncol Biol Phys 2002;52:496-513. [Crossref] [PubMed]
4. Ayers DC, Pellegrini VD Jr, Evarts CM. Prevention of heterotopic ossification in high-risk patients by radiation therapy. Clin Orthop Relat Res 1991;87-93. [Crossref] [PubMed]
5. Yamamoto S, Komiya S, Inoue A. Clinicopathological study of subungual exostosis. The Japanese Journal of Orthopedics and Traumatology. 1992;41:549-52. [Crossref]
6. Toga M, Hosaka Y, Sato K, et al. Six cases of subungual exostosis. Journal of the Showa Medical Association 1989;49:111-7.
7. Evison G, Price CH. Subungual exostosis. Br J Radiol 1966;39:451-5. [Crossref] [PubMed]
8. Chiheb S, Slimani Y, Karam R, et al. Subungual Exostosis: A Case Series of 48 Patients. Skin Appendage Disord 2021;7:475-9. [Crossref] [PubMed]
9. Dąbrowski M, Rusek D, Dańczak-Pazdrowska A, et al. The Influence of Clinical Factors on Treatment Outcome and a Recurrence of Surgically Removed Protruded Subungual Osteochondroma and Subungual Exostosis. J Clin Med 2023;12:6413. [Crossref] [PubMed]
10. Shimodaira H, Fujioka F, Matsubara M. Outcome of surgical treatment for subungual exostosis by open method. The Japanese Journal of Orthopedic Surgery 2013;64:607-10.
11. Maender C, Sahajpal D, Wright TW. Treatment of heterotopic ossification of the elbow following burn injury: recommendations for surgical excision and perioperative prophylaxis using radiation therapy. J Shoulder Elbow Surg 2010;19:1269-75. [Crossref] [PubMed]
12. Sun Y, Cai J, Li F, et al. The efficacy of celecoxib in preventing heterotopic ossification recurrence after open arthrolysis for post-traumatic elbow stiffness in adults. J Shoulder Elbow Surg 2015;24:1735-40. [Crossref] [PubMed]
13. Cipriano C, Pill SG, Rosenstock J, et al. Radiation therapy for preventing recurrence of neurogenic heterotopic ossification. Orthopedics 2009;32: [Crossref] [PubMed]
14. Jansen JT, Broerse JJ, Zoetelief J, et al. Estimation of the carcinogenic risk of radiotherapy of benign diseases from shoulder to heel. Radiother Oncol 2005;76:270-7. [Crossref] [PubMed]