BJD
British Journal of Dermatology
C L I N I C A L A N D LA B O R A T O R Y I N V E S T I G A T I O N S
Subungual corn: a tender pigmented subungual lesion in older people D.A.R. de Berker,1 C. Wlodek1 and I.R. Bristow2 1 2
Bristol Dermatology Centre, Bristol Royal Infirmary, Bristol BS6 7EL, U.K. School of Health Sciences, University of Southampton, Southampton SO17 1BJ, U.K.
Summary Correspondence David de Berker. E-mail: [email protected]
Accepted for publication 26 January 2014
Funding sources None.
Conflicts of interest None declared. DOI 10.1111/bjd.12858
Background Heloma durum occurs as a tender mass in the distal nail bed beneath the big toenail in older women. Objectives To define and report a variant of heloma durum not referenced in the literature. Methods This was a retrospective study whereby records, including photographs, of all cases of subungual corn were reviewed. All patients were seen in an outpatient setting. Results The records of 16 patients [15 women, one man, mean age 68 years (range 49–87)] were examined; history was between 6 and 30 months, none of the patients had received effective treatment. Mycology was negative. All reported discomfort under the big toe nail; 12 had associated subungual haemorrhage. The right big toenail was involved in 10 of 16 patients. Shared clinical features were of a subungual focus of hyperkeratosis (100%) with haemorrhage admixed in 75% of cases. The lesion was in the midline third of the nail in 11 of 16 patients (69%). The affected distal margin of nail was the uppermost point in the lateral profile of the toe (100%). Hyperextension at the distal interphalangeal joint of the affected toe was demonstrated with the patient standing. Local excision was performed when diagnosis was unclear (eight patients); simple clearance of the keratin plug was performed in the other eight patients. There was no relapse in patients who were followed up for > 6 months (n = 7). Conclusions Clinical explanation and paring down should be attempted in order to avoid surgery at this poor healing site in the elderly.
What’s already known about this topic?
•
A corn is recognized as a focal hyperplasia of skin, typically on the foot, that causes pain.
What does this study add?
•
This is the first peer-reviewed publication to provide a case series of subungual corns, including diagnostic characteristics, histology and management.
Pigmented or painful lesions beneath the nail raise the possibility of a diagnosis of malignancy. The differential diagnosis of a pigmented lesion includes melanoma,1 with the hallux being the most commonly involved digit.2 Foot pain in the elderly can result in the loss of mobility, with significant implications for long-term well-being,3 and risks of osteoporosis and hip fracture.4 We provide data on the observations © 2014 British Association of Dermatologists
made by a hospital-based dermatologist with a specialist interest in nail pathology. The aim of this report is to enable patients, referred with possible malignancy or pain, to be identified early on clinical grounds, to relieve their symptoms and to differentiate them from having other pathologies that may need more invasive assessment and management. British Journal of Dermatology (2014) 171, pp69–72
69
70 Subungual corn: a tender pigmented subungual lesion in older people, D.A.R. de Berker et al.
We performed a retrospective analysis of a diagnostic grouping based on a prospective imaging archive process. Over the 20-year period 1993–2013, patients presenting with atypical subungual lesions had images taken during their first attendance at a university teaching dermatology clinic. Diagnosis was established through clinical assessment, biopsy (where needed), consultation with podiatry and clinical evolution. Patients were offered follow-up. Data were collected as part of the clinical and image record. No patients with relevant presenting characteristics were excluded. Diagnostic criteria evolved with increasing knowledge of the pathology. Clinical characteristics of note were female sex, middle age and older, pain, subungual focal pathology, the presence of pigment, great toenail involvement and the geometry of the distal interphalangeal joint. Images and histories were shared with an expert in foot biomechanics to test the interpretation and diminish bias. The study size was estimated to be appropriate for a clinical descriptive series in order to establish diagnostic criteria in a rare disease with consistent findings. No formal statistics were applied to the data. Details were limited to digit, age, sex and the clinical features seen on photography in five patients – lost notes and death hindered the capture of more complete data.
exacerbated in the winter when wearing more heavy, closed shoes. None of the patients reported effective treatment. Pain was demonstrated during examination by pressing on the nail directly over the pathology. Clinical features included a distal subungual focus of hyperkeratosis (100%), with haemorrhage admixed in 12 of 16 patients (75%), as confirmed by the clinical or histological characteristics (Fig. 1), or examination (using dermoscopy) of the nail from the free edge. The lesion was located in the midline third of the nail in 11 of 16 patients (69%). The affected distal margin of the nail was the uppermost point in the lateral profile of the toe in all patients. Hyperextension at the distal interphalangeal joint of the affected toe was demonstrated clinically with the patient standing (Fig. 2a). Local excision was performed in eight patients. Histology showed epithelial hyperplasia and orthokeratosis with parakeratosis. Haemorrhagic and eosinophilic material, consistent with dried exudate, was seen within the keratin layer. There was minimal inflammation, and no features of dysplasia or psoriasis. In the other eight patients, simple clearance of the keratin plug was provided along with clipping of the overlying nail. Patients were advised to seek podiatric advice on foot care and suitable footwear. There was no relapse in patients who were followed up for more than 6 months (n = 7). Podiatric management comprised a three-part plan (Table 1).
Results
Discussion
Fifteen women and one man [mean age 68 years (range 49– 87)] were diagnosed with a subungual corn (15 big toe, one second toe). The histories obtained were between 6 and 30 months. None of the patients had generalized nail disease. Two patients had type 2 diabetes mellitus, and a further patient had neuropathy. None had significant peripheral vascular disease. All patients presented with symptoms ranging from discomfort to pain, which were relieved when wearing open-toed sandals or no footwear, and which were typically
We document the clinical features of a rare subungual pathology not formally described in the dermatological literature. Given the timescale and nature of the data collection, the details included herein are not comprehensive; however, they give a clear description of the central features that enable identification of this specific entity. The medical definitions of ‘corn’, ‘heloma’, ‘clavus’ and ‘callus’ are inconsistent across different specialties. A corn and heloma are the same thing – a circumscribed, sharply
Patients and methods
(a)
(b)
(c)
(d)
Fig 1. Classic subungual corn demonstrating (a) the pigment seen through nail and (b) a keratinous plug visible at the free edge. (c, d) Clipping back reveals keratin and a haemorrhagic mass, which can be enucleated. British Journal of Dermatology (2014) 171, pp69–72
© 2014 British Association of Dermatologists
Subungual corn: a tender pigmented subungual lesion in older people, D.A.R. de Berker et al. 71
(a)
(b)
(c)
Fig 2. Hyperextension at (a) the distal interphalangeal joint is a factor in distal nail plate trauma and can be associated with fixation of (b) the metatarsophalangeal joint (adapted from Lemont and Sorrento).11 Lemont and Sorrento11 report the clinical observation of a transverse crease over the joint and osteoarthritic fusion of the associated metatarsophalangeal joint. The crease is a sign of an adaptive mechanism of the big toe during walking. Normally, the hallux would dorsiflex approximately 60–75° over the head of the first metatarsal. When this is prevented through fusion, the dorsiflexion (extension) is achieved at the distal interphalangeal joint by pitching the tip of the toe upwards, rather than tilting the foot forward at the metatarsophalangeal joint. (c) Formation of subungual corn: typical hyperextended toe anatomy leading to subungual hyperkeratotic lesion formation at the point of recurrent trauma and callus formation.
Table 1 Three-point plan for the clinical management of subungual corn Guidance on footwear
Local wedges and orthotics
Ongoing podiatric foot care
A high ‘box’ providing space in the distal shoe to accommodate the extended toe, with little or no internal stitching to rub on the affected toe No significant heel on footwear
Pre-existing mechanical and joint problems (e.g. osteoarthritis and hallux valgus) in the foot may benefit from orthotic devices to realign the foot during gait Arch supports can ‘shorten’ a flattened foot, reducing distal nail trauma Silicone orthodigital devices can realign flexible toe deformity
Nail reduction using a nail drill, along with sharp enucleation (debridement) of the corn, can offer an immediate reduction in pain Podiatric surgical procedures can correct precipitating digital deformity permanently –
Soft or double socks
demarcated area of hyperkeratosis with a translucent core.5,6 A clavus or callus has a broad base without clear demarcation, typically found beneath the metatarsal head. Two types of heloma are described in the podiatric literature: heloma durum and heloma molle.7,8 Heloma molle is a soft corn where macerated hyperkeratosis secondary to trauma creates a painful nodule in the webspace, usually of the fourth and fifth toes. We report a variant of heloma durum that is described in early chiropody texts,9,10 but that is not referenced in the peer-reviewed literature. As we have © 2014 British Association of Dermatologists
demonstrated, the subungual corn occurs as a tender mass in the distal nail bed beneath the big toenail in older women. End-on dermoscopy at the nail edge will usually confirm the features of haemorrhage entrapped within keratin and a well-demarcated edge of normal skin. Hyperextension at the distal interphalangeal joint is an associated feature, and the biomechanics are alluded to by Lemont and Sorrento (Fig. 2).11 Subungual corn is rarely recognized. Instead, it is typically referred to as a possible malignancy given the associated pain British Journal of Dermatology (2014) 171, pp69–72
72 Subungual corn: a tender pigmented subungual lesion in older people, D.A.R. de Berker et al.
and haemorrhage. The importance of a clear diagnosis rests, in part, on the need to exclude a malignancy, where the pigment might represent a melanoma, and pain with nail bed hyperkeratosis could be a feature of subungual squamous carcinoma.12 Recent professional guidelines in podiatry have highlighted the need for a precise diagnosis for nonresolving pathologies of the foot.13 Where there is doubt, podiatrists are advised to refer patients for dermatological assessment. Awareness of the diagnostic features of subungual corn is part of the knowledge set for subungual diseases of the foot. Other benign pathologies with overlapping features include subungual exostosis and viral wart. If there is doubt, excisional biopsy will clarify the diagnosis. Histopathology of this variant of corn is the same as that seen at other sites.14 The pathology can be explained by the wearing of incompatible footwear, where trauma is caused to the toe by repetitive contact with the upper part of the shoe (Fig. 2c). When coupled with measures to prevent relapse, excision is one avenue of management. Surgery of the foot in this age group can be complicated by poor healing in connection with diabetic or vascular premorbidities; any biopsy should be preceded by careful assessment and wound care planning. Conservative management is by way of a three-part plan (Table 1).15 In summary, the diagnosis and management of subungual corn requires collaboration between the general practitioner, the dermatologist and the podiatrist, where no single specialty is an expert in all aspects of the disease. Recognition and management can help avoid pain and maintain mobility.
References 1 Tosti A, Piraccini BM, de Farias DC. Dealing with melanonychia. Semin Cutan Med Surg 2009; 28:49–54.
British Journal of Dermatology (2014) 171, pp69–72
2 Tan KB, Moncrieff M, Thompson JF et al. Subungual melanoma: a study of 124 cases highlighting features of early lesions, potential pitfalls in diagnosis, and guidelines for histologic reporting. Am J Surg Pathol 2007; 31:1902–12. 3 Benevenutti F, Ferrucci L, Guralnik J. Foot pain and disability in elderly persons: an epidemiologic survey. J Am Geriatr Soc 1995; 43:479–84. 4 Menz HB, Lord SR. The contribution of foot problems to mobility impairment and falls in community-dwelling older people. J Am Geriatr Soc 2001; 49:1651–6. 5 Singh D, Bentley G, Trevino SG. Callosities, corns, and calluses. BMJ 1996; 312:1403–6. 6 Dagnall JC. Corn or heloma? Br Chirop J 1959; 24:42–3. 7 Freeman D. Corns and calluses resulting from mechanical hyperkeratosis. Am Fam Physician 2002; 65:2277–80. 8 Roven MD. Helomata, a review of some of the literature. J Am Podiatry Assoc 1968; 58:209–13. 9 Charlesworth F. Chiropody: Theory & Practice. London: Actinic Press, 1954. 10 Gross RH, Burnett EK. The Practice of Podiatry. New York, NY: Harriman, 1933. 11 Lemont H, Sorrento DL. Clinical pearl: accentuated transverse hallucal skin crease – a cutaneous skin marker for hallux rigidus (osteoarthritis of the big toe joint). J Am Acad Dermatol 1999; 40:631–2. 12 Dalle S, Depape L, Phan A et al. Squamous cell carcinoma of the nail apparatus: clinicopathological study of 35 cases. Br J Dermatol 2007; 156:871–4. 13 Bristow IR, de Berker DA, Acland KM et al. Clinical guidelines for the recognition of melanoma of the foot and nail unit. J Foot Ankle Res 2010; 3:25. 14 Bonavilla EJ. Histopathology of the heloma durum: some significant features and their implications. J Am Podiatry Assoc 1968; 58:423–7. 15 Scullion PG. Dermatologic review: scalpel technique in removing heloma and hyperkeratosis. J Foot Surg 1984; 23:344–9.
© 2014 British Association of Dermatologists
British Journal of Dermatology
C L I N I C A L A N D LA B O R A T O R Y I N V E S T I G A T I O N S
Subungual corn: a tender pigmented subungual lesion in older people D.A.R. de Berker,1 C. Wlodek1 and I.R. Bristow2 1 2
Bristol Dermatology Centre, Bristol Royal Infirmary, Bristol BS6 7EL, U.K. School of Health Sciences, University of Southampton, Southampton SO17 1BJ, U.K.
Summary Correspondence David de Berker. E-mail: [email protected]
Accepted for publication 26 January 2014
Funding sources None.
Conflicts of interest None declared. DOI 10.1111/bjd.12858
Background Heloma durum occurs as a tender mass in the distal nail bed beneath the big toenail in older women. Objectives To define and report a variant of heloma durum not referenced in the literature. Methods This was a retrospective study whereby records, including photographs, of all cases of subungual corn were reviewed. All patients were seen in an outpatient setting. Results The records of 16 patients [15 women, one man, mean age 68 years (range 49–87)] were examined; history was between 6 and 30 months, none of the patients had received effective treatment. Mycology was negative. All reported discomfort under the big toe nail; 12 had associated subungual haemorrhage. The right big toenail was involved in 10 of 16 patients. Shared clinical features were of a subungual focus of hyperkeratosis (100%) with haemorrhage admixed in 75% of cases. The lesion was in the midline third of the nail in 11 of 16 patients (69%). The affected distal margin of nail was the uppermost point in the lateral profile of the toe (100%). Hyperextension at the distal interphalangeal joint of the affected toe was demonstrated with the patient standing. Local excision was performed when diagnosis was unclear (eight patients); simple clearance of the keratin plug was performed in the other eight patients. There was no relapse in patients who were followed up for > 6 months (n = 7). Conclusions Clinical explanation and paring down should be attempted in order to avoid surgery at this poor healing site in the elderly.
What’s already known about this topic?
•
A corn is recognized as a focal hyperplasia of skin, typically on the foot, that causes pain.
What does this study add?
•
This is the first peer-reviewed publication to provide a case series of subungual corns, including diagnostic characteristics, histology and management.
Pigmented or painful lesions beneath the nail raise the possibility of a diagnosis of malignancy. The differential diagnosis of a pigmented lesion includes melanoma,1 with the hallux being the most commonly involved digit.2 Foot pain in the elderly can result in the loss of mobility, with significant implications for long-term well-being,3 and risks of osteoporosis and hip fracture.4 We provide data on the observations © 2014 British Association of Dermatologists
made by a hospital-based dermatologist with a specialist interest in nail pathology. The aim of this report is to enable patients, referred with possible malignancy or pain, to be identified early on clinical grounds, to relieve their symptoms and to differentiate them from having other pathologies that may need more invasive assessment and management. British Journal of Dermatology (2014) 171, pp69–72
69
70 Subungual corn: a tender pigmented subungual lesion in older people, D.A.R. de Berker et al.
We performed a retrospective analysis of a diagnostic grouping based on a prospective imaging archive process. Over the 20-year period 1993–2013, patients presenting with atypical subungual lesions had images taken during their first attendance at a university teaching dermatology clinic. Diagnosis was established through clinical assessment, biopsy (where needed), consultation with podiatry and clinical evolution. Patients were offered follow-up. Data were collected as part of the clinical and image record. No patients with relevant presenting characteristics were excluded. Diagnostic criteria evolved with increasing knowledge of the pathology. Clinical characteristics of note were female sex, middle age and older, pain, subungual focal pathology, the presence of pigment, great toenail involvement and the geometry of the distal interphalangeal joint. Images and histories were shared with an expert in foot biomechanics to test the interpretation and diminish bias. The study size was estimated to be appropriate for a clinical descriptive series in order to establish diagnostic criteria in a rare disease with consistent findings. No formal statistics were applied to the data. Details were limited to digit, age, sex and the clinical features seen on photography in five patients – lost notes and death hindered the capture of more complete data.
exacerbated in the winter when wearing more heavy, closed shoes. None of the patients reported effective treatment. Pain was demonstrated during examination by pressing on the nail directly over the pathology. Clinical features included a distal subungual focus of hyperkeratosis (100%), with haemorrhage admixed in 12 of 16 patients (75%), as confirmed by the clinical or histological characteristics (Fig. 1), or examination (using dermoscopy) of the nail from the free edge. The lesion was located in the midline third of the nail in 11 of 16 patients (69%). The affected distal margin of the nail was the uppermost point in the lateral profile of the toe in all patients. Hyperextension at the distal interphalangeal joint of the affected toe was demonstrated clinically with the patient standing (Fig. 2a). Local excision was performed in eight patients. Histology showed epithelial hyperplasia and orthokeratosis with parakeratosis. Haemorrhagic and eosinophilic material, consistent with dried exudate, was seen within the keratin layer. There was minimal inflammation, and no features of dysplasia or psoriasis. In the other eight patients, simple clearance of the keratin plug was provided along with clipping of the overlying nail. Patients were advised to seek podiatric advice on foot care and suitable footwear. There was no relapse in patients who were followed up for more than 6 months (n = 7). Podiatric management comprised a three-part plan (Table 1).
Results
Discussion
Fifteen women and one man [mean age 68 years (range 49– 87)] were diagnosed with a subungual corn (15 big toe, one second toe). The histories obtained were between 6 and 30 months. None of the patients had generalized nail disease. Two patients had type 2 diabetes mellitus, and a further patient had neuropathy. None had significant peripheral vascular disease. All patients presented with symptoms ranging from discomfort to pain, which were relieved when wearing open-toed sandals or no footwear, and which were typically
We document the clinical features of a rare subungual pathology not formally described in the dermatological literature. Given the timescale and nature of the data collection, the details included herein are not comprehensive; however, they give a clear description of the central features that enable identification of this specific entity. The medical definitions of ‘corn’, ‘heloma’, ‘clavus’ and ‘callus’ are inconsistent across different specialties. A corn and heloma are the same thing – a circumscribed, sharply
Patients and methods
(a)
(b)
(c)
(d)
Fig 1. Classic subungual corn demonstrating (a) the pigment seen through nail and (b) a keratinous plug visible at the free edge. (c, d) Clipping back reveals keratin and a haemorrhagic mass, which can be enucleated. British Journal of Dermatology (2014) 171, pp69–72
© 2014 British Association of Dermatologists
Subungual corn: a tender pigmented subungual lesion in older people, D.A.R. de Berker et al. 71
(a)
(b)
(c)
Fig 2. Hyperextension at (a) the distal interphalangeal joint is a factor in distal nail plate trauma and can be associated with fixation of (b) the metatarsophalangeal joint (adapted from Lemont and Sorrento).11 Lemont and Sorrento11 report the clinical observation of a transverse crease over the joint and osteoarthritic fusion of the associated metatarsophalangeal joint. The crease is a sign of an adaptive mechanism of the big toe during walking. Normally, the hallux would dorsiflex approximately 60–75° over the head of the first metatarsal. When this is prevented through fusion, the dorsiflexion (extension) is achieved at the distal interphalangeal joint by pitching the tip of the toe upwards, rather than tilting the foot forward at the metatarsophalangeal joint. (c) Formation of subungual corn: typical hyperextended toe anatomy leading to subungual hyperkeratotic lesion formation at the point of recurrent trauma and callus formation.
Table 1 Three-point plan for the clinical management of subungual corn Guidance on footwear
Local wedges and orthotics
Ongoing podiatric foot care
A high ‘box’ providing space in the distal shoe to accommodate the extended toe, with little or no internal stitching to rub on the affected toe No significant heel on footwear
Pre-existing mechanical and joint problems (e.g. osteoarthritis and hallux valgus) in the foot may benefit from orthotic devices to realign the foot during gait Arch supports can ‘shorten’ a flattened foot, reducing distal nail trauma Silicone orthodigital devices can realign flexible toe deformity
Nail reduction using a nail drill, along with sharp enucleation (debridement) of the corn, can offer an immediate reduction in pain Podiatric surgical procedures can correct precipitating digital deformity permanently –
Soft or double socks
demarcated area of hyperkeratosis with a translucent core.5,6 A clavus or callus has a broad base without clear demarcation, typically found beneath the metatarsal head. Two types of heloma are described in the podiatric literature: heloma durum and heloma molle.7,8 Heloma molle is a soft corn where macerated hyperkeratosis secondary to trauma creates a painful nodule in the webspace, usually of the fourth and fifth toes. We report a variant of heloma durum that is described in early chiropody texts,9,10 but that is not referenced in the peer-reviewed literature. As we have © 2014 British Association of Dermatologists
demonstrated, the subungual corn occurs as a tender mass in the distal nail bed beneath the big toenail in older women. End-on dermoscopy at the nail edge will usually confirm the features of haemorrhage entrapped within keratin and a well-demarcated edge of normal skin. Hyperextension at the distal interphalangeal joint is an associated feature, and the biomechanics are alluded to by Lemont and Sorrento (Fig. 2).11 Subungual corn is rarely recognized. Instead, it is typically referred to as a possible malignancy given the associated pain British Journal of Dermatology (2014) 171, pp69–72
72 Subungual corn: a tender pigmented subungual lesion in older people, D.A.R. de Berker et al.
and haemorrhage. The importance of a clear diagnosis rests, in part, on the need to exclude a malignancy, where the pigment might represent a melanoma, and pain with nail bed hyperkeratosis could be a feature of subungual squamous carcinoma.12 Recent professional guidelines in podiatry have highlighted the need for a precise diagnosis for nonresolving pathologies of the foot.13 Where there is doubt, podiatrists are advised to refer patients for dermatological assessment. Awareness of the diagnostic features of subungual corn is part of the knowledge set for subungual diseases of the foot. Other benign pathologies with overlapping features include subungual exostosis and viral wart. If there is doubt, excisional biopsy will clarify the diagnosis. Histopathology of this variant of corn is the same as that seen at other sites.14 The pathology can be explained by the wearing of incompatible footwear, where trauma is caused to the toe by repetitive contact with the upper part of the shoe (Fig. 2c). When coupled with measures to prevent relapse, excision is one avenue of management. Surgery of the foot in this age group can be complicated by poor healing in connection with diabetic or vascular premorbidities; any biopsy should be preceded by careful assessment and wound care planning. Conservative management is by way of a three-part plan (Table 1).15 In summary, the diagnosis and management of subungual corn requires collaboration between the general practitioner, the dermatologist and the podiatrist, where no single specialty is an expert in all aspects of the disease. Recognition and management can help avoid pain and maintain mobility.
References 1 Tosti A, Piraccini BM, de Farias DC. Dealing with melanonychia. Semin Cutan Med Surg 2009; 28:49–54.
British Journal of Dermatology (2014) 171, pp69–72
2 Tan KB, Moncrieff M, Thompson JF et al. Subungual melanoma: a study of 124 cases highlighting features of early lesions, potential pitfalls in diagnosis, and guidelines for histologic reporting. Am J Surg Pathol 2007; 31:1902–12. 3 Benevenutti F, Ferrucci L, Guralnik J. Foot pain and disability in elderly persons: an epidemiologic survey. J Am Geriatr Soc 1995; 43:479–84. 4 Menz HB, Lord SR. The contribution of foot problems to mobility impairment and falls in community-dwelling older people. J Am Geriatr Soc 2001; 49:1651–6. 5 Singh D, Bentley G, Trevino SG. Callosities, corns, and calluses. BMJ 1996; 312:1403–6. 6 Dagnall JC. Corn or heloma? Br Chirop J 1959; 24:42–3. 7 Freeman D. Corns and calluses resulting from mechanical hyperkeratosis. Am Fam Physician 2002; 65:2277–80. 8 Roven MD. Helomata, a review of some of the literature. J Am Podiatry Assoc 1968; 58:209–13. 9 Charlesworth F. Chiropody: Theory & Practice. London: Actinic Press, 1954. 10 Gross RH, Burnett EK. The Practice of Podiatry. New York, NY: Harriman, 1933. 11 Lemont H, Sorrento DL. Clinical pearl: accentuated transverse hallucal skin crease – a cutaneous skin marker for hallux rigidus (osteoarthritis of the big toe joint). J Am Acad Dermatol 1999; 40:631–2. 12 Dalle S, Depape L, Phan A et al. Squamous cell carcinoma of the nail apparatus: clinicopathological study of 35 cases. Br J Dermatol 2007; 156:871–4. 13 Bristow IR, de Berker DA, Acland KM et al. Clinical guidelines for the recognition of melanoma of the foot and nail unit. J Foot Ankle Res 2010; 3:25. 14 Bonavilla EJ. Histopathology of the heloma durum: some significant features and their implications. J Am Podiatry Assoc 1968; 58:423–7. 15 Scullion PG. Dermatologic review: scalpel technique in removing heloma and hyperkeratosis. J Foot Surg 1984; 23:344–9.
© 2014 British Association of Dermatologists
