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Sublingual epidermal cyst
Subungual epidermal cyst Cheuk W. Yung, M.D ., * and Stephen A. Estes. M.D. Cincinnati. OH A patient developed a painful subungual lesion which was an epidermal cyst on biopsy. The incidence and pathogenesis of subungual epidermal cysts are reviewed. This usually asymptomatic tumor should be con sidered in the differential diagnosis of subungual lesions. (J AM ACAD DERMATOL 3:599-601. 1980.) .
Subungual epidermal cysts , usually asymptomatic and associated with fingernail clubbing, are commonly found in autopsy nail studies . I-a Painful subungual epidermal cysts are rare and should not be confused with other more common entities . This is a report of a patient with painful subungual epidermal cysts and discussion of possible etiologies. CASE REPORT A 27-year-old male medical student had an asymptomatic subungual lesion on the left middle finger for 3 years . Over the preceding 9 months, the lesion increased in size. For several weeks he experienced shooting pain radiating from the subungual area to the base of the finger. He denied any paresthesia. hyperesthesia. or swelling in the involved area. The patient's mother recalled that at the age of 2 his left. middle. and ring fingers were smashed in the car door. No complications or nail deformity was noted after the injury. The patient denied any other trauma. nail biting, or frequent chemical contact. On physical examination there was a subungual yellowish white discoloration 3 x3 mm, located near the lunula of the left middle finger. There was mild tenderness on pressure. no clubbing, edema, or erythema around the middle finger. no nail deformities or skeletal abnormalities . Radiographic studies of the fingers were normal. From the Department of Dermatology, University of Cincinnati Medical Center. Reprint requests to: Dr. Stephen A. Estes , 234 Goodman A\'e ., Pavilion A, Room 315 , Cincinnati, OH 45267/513-872-4310. *Now at the Section of Dermatology, Department of Medici ne, the University of Chicago Pritzker School of Medicine, Chicago, IL.
0190-9622/80/120599+03S00.30/0 © 1980 Am Acad Dermatol
Glomus tumor was considered clinically. and a 4-mm punch biopsy was performed. Microscopic examination of the biopsy revealed two cystic struclures in the dermis lined by squamous epithelium with a granular layer. and containing keratin malerial centrally (Fig. I) . The painful symptoms resolved after biopsy and the nail healed normally without deformity. The patient was follo wed for a period'of I year without recurrence.
COMMENT
Subungual epidermal cyst s, or subungual epidermoid inclusions, are seldom mentioned in the dermatologic literature in the differential diagnosis of subungual lesions. They were first described by Lewin 1 in the fingernail and by Sarnmarr' in the toenail . Lewin studied ninety consecutive nails at autopsy and found subungual epidermal cysts in all patients who clinically had fingernail clubbing; however, they were also found in many normal nails. 2 •3 All the epidermal cysts were of microscopic size and showed no accompanying gross abnormalities of the overlying nail. No general disease was found to be associated with the presence of these epidermal cyst s. except for the clinical sign of fingernail clubbing. No history of local trauma, nail disorders, or previous skin disease correlated with the presence of cysts . Microscopically, epidermal cysts at different stages of development were seen. The earliest change Lewin " noted was one of bulbous proliferation of basal cells at the tips of the rete ridges. As they enlarged, they evolved into · typical epidermal
599
600
rung and Estes
Journal of the American Academy of Dermatology
Fig. 1. Histologic section of the subungual lesion showing two cystic structures in the dermis lined by squamous epithelium with a granular layer and containing keratin material centrally. (Hematoxylin-eosin stain; X 10.)
cysts, lined by a granular layer and showing central keratinization and degeneration. The etiology of subungual epidermal cysts is poorly understood. Sarnrnarr' suggested that trauma may be a cause. This hypothesis is supported by the surgical case reported by Lewin" in which a history of trauma appeared to be associated with the development of the lesion . The present case supports this theory. It is worthwhile to note that our patient was asymptomatic after a recalled traumatic episode 25 years previously. Whether a causal relationship is real or not is highly questionable. In Lewin's study of epidermal inclusion cysts , there was no evidence of trauma histologically or traumatic implantation of epidermis into dermis . Instead, epithelial proliferation at the tips of rete ridges appeared to be the developmental
sequence. Since proliferation of dermal fibroblasts also occurred in clubbing, a common proliferative factor affecting the whole nail bed was suggested .t -' What causes this proliferation is unknown; it may be trauma or some obscure intrinsic factor. No one theory has yet satisfactorily explained the occurrence of subungual epidermal cysts. The pathogenesis of any epidermal cyst has been the topic of much debate. In the past, it has been labeled as a retention cyst. The lack of adnexal structures in the subungual area would appear to make the retention cyst theory less likely. Epstein and Kligman" clearly showed that it simply represents a keratinizing type of tumor arising from equipotential cells anywhere in the cutaneous epithelial system.
Volume 3 Number 6 December, 1980
Epidermoid cyst of the distal phalanx is a rare disease and should not be confused with subungual epidermal cyst. The former entity clinically presents as a painful, enlarged distal phalanx associated with a history of recent trauma. Diagnostic x-ray and histologic examinations show that these lesions arise directly from the bony structure of the phalanx, permitting differentiation from subungual epidermal cysts.?" Subungual epidermal cysts may be a more common entity than previously recognized. Most of the lesions are asymptomatic; however,occasionally one may encounter symptomatic subungual epidermal cysts. Differential diagnosis of subungual lesions should include cellular nevus, malignant melanoma, keratoacanthoma, epidermoid cyst of the distal phalanx, primary squamous cell carcinoma, glomus tumor, enchondroma, and
Subungual epidermal cyst
601
metastatic carcinoma. A biopsy can easily be done on such lesions. This may be both diagnostic and therapeutic, as illustrated in this case report. REFERENCES I. Lewin K: The normal finger nail. Br J Dermatol 77:421430, 1965. 2. Lewin K: The finger nail in general disease: A macroscopic and microscopic study of 87 consecutive autopsies. Br J Dermatol 77:431-438, 1965. 3. Lewin K: Subungual epidermoid inclusions. Br J Dermatol 81:671-675, 1969. 4. Samman PD: The human toe nail, its genesis and blood supply. Br J Dermatol 71:296-302, 1959. 5. Epstein W, Kligman A: The pathogenesis of milia and benign tumors of the skin. J Invest DermatoI26:1-II, 1956. 6. Zadek I, Cohen HG: Epidermoid cyst of the terminal phalanx of a finger. Am J Surg 85:771-774, 1953. 7. St Onge RA, Jackson IT: An uncommon sequel to thumb trauma: Epidermoid cyst. Hand 9:52-56, 1977.
Subungual epidermal cysts , usually asymptomatic and associated with fingernail clubbing, are commonly found in autopsy nail studies . I-a Painful subungual epidermal cysts are rare and should not be confused with other more common entities . This is a report of a patient with painful subungual epidermal cysts and discussion of possible etiologies. CASE REPORT A 27-year-old male medical student had an asymptomatic subungual lesion on the left middle finger for 3 years . Over the preceding 9 months, the lesion increased in size. For several weeks he experienced shooting pain radiating from the subungual area to the base of the finger. He denied any paresthesia. hyperesthesia. or swelling in the involved area. The patient's mother recalled that at the age of 2 his left. middle. and ring fingers were smashed in the car door. No complications or nail deformity was noted after the injury. The patient denied any other trauma. nail biting, or frequent chemical contact. On physical examination there was a subungual yellowish white discoloration 3 x3 mm, located near the lunula of the left middle finger. There was mild tenderness on pressure. no clubbing, edema, or erythema around the middle finger. no nail deformities or skeletal abnormalities . Radiographic studies of the fingers were normal. From the Department of Dermatology, University of Cincinnati Medical Center. Reprint requests to: Dr. Stephen A. Estes , 234 Goodman A\'e ., Pavilion A, Room 315 , Cincinnati, OH 45267/513-872-4310. *Now at the Section of Dermatology, Department of Medici ne, the University of Chicago Pritzker School of Medicine, Chicago, IL.
0190-9622/80/120599+03S00.30/0 © 1980 Am Acad Dermatol
Glomus tumor was considered clinically. and a 4-mm punch biopsy was performed. Microscopic examination of the biopsy revealed two cystic struclures in the dermis lined by squamous epithelium with a granular layer. and containing keratin malerial centrally (Fig. I) . The painful symptoms resolved after biopsy and the nail healed normally without deformity. The patient was follo wed for a period'of I year without recurrence.
COMMENT
Subungual epidermal cyst s, or subungual epidermoid inclusions, are seldom mentioned in the dermatologic literature in the differential diagnosis of subungual lesions. They were first described by Lewin 1 in the fingernail and by Sarnmarr' in the toenail . Lewin studied ninety consecutive nails at autopsy and found subungual epidermal cysts in all patients who clinically had fingernail clubbing; however, they were also found in many normal nails. 2 •3 All the epidermal cysts were of microscopic size and showed no accompanying gross abnormalities of the overlying nail. No general disease was found to be associated with the presence of these epidermal cyst s. except for the clinical sign of fingernail clubbing. No history of local trauma, nail disorders, or previous skin disease correlated with the presence of cysts . Microscopically, epidermal cysts at different stages of development were seen. The earliest change Lewin " noted was one of bulbous proliferation of basal cells at the tips of the rete ridges. As they enlarged, they evolved into · typical epidermal
599
600
rung and Estes
Journal of the American Academy of Dermatology
Fig. 1. Histologic section of the subungual lesion showing two cystic structures in the dermis lined by squamous epithelium with a granular layer and containing keratin material centrally. (Hematoxylin-eosin stain; X 10.)
cysts, lined by a granular layer and showing central keratinization and degeneration. The etiology of subungual epidermal cysts is poorly understood. Sarnrnarr' suggested that trauma may be a cause. This hypothesis is supported by the surgical case reported by Lewin" in which a history of trauma appeared to be associated with the development of the lesion . The present case supports this theory. It is worthwhile to note that our patient was asymptomatic after a recalled traumatic episode 25 years previously. Whether a causal relationship is real or not is highly questionable. In Lewin's study of epidermal inclusion cysts , there was no evidence of trauma histologically or traumatic implantation of epidermis into dermis . Instead, epithelial proliferation at the tips of rete ridges appeared to be the developmental
sequence. Since proliferation of dermal fibroblasts also occurred in clubbing, a common proliferative factor affecting the whole nail bed was suggested .t -' What causes this proliferation is unknown; it may be trauma or some obscure intrinsic factor. No one theory has yet satisfactorily explained the occurrence of subungual epidermal cysts. The pathogenesis of any epidermal cyst has been the topic of much debate. In the past, it has been labeled as a retention cyst. The lack of adnexal structures in the subungual area would appear to make the retention cyst theory less likely. Epstein and Kligman" clearly showed that it simply represents a keratinizing type of tumor arising from equipotential cells anywhere in the cutaneous epithelial system.
Volume 3 Number 6 December, 1980
Epidermoid cyst of the distal phalanx is a rare disease and should not be confused with subungual epidermal cyst. The former entity clinically presents as a painful, enlarged distal phalanx associated with a history of recent trauma. Diagnostic x-ray and histologic examinations show that these lesions arise directly from the bony structure of the phalanx, permitting differentiation from subungual epidermal cysts.?" Subungual epidermal cysts may be a more common entity than previously recognized. Most of the lesions are asymptomatic; however,occasionally one may encounter symptomatic subungual epidermal cysts. Differential diagnosis of subungual lesions should include cellular nevus, malignant melanoma, keratoacanthoma, epidermoid cyst of the distal phalanx, primary squamous cell carcinoma, glomus tumor, enchondroma, and
Subungual epidermal cyst
601
metastatic carcinoma. A biopsy can easily be done on such lesions. This may be both diagnostic and therapeutic, as illustrated in this case report. REFERENCES I. Lewin K: The normal finger nail. Br J Dermatol 77:421430, 1965. 2. Lewin K: The finger nail in general disease: A macroscopic and microscopic study of 87 consecutive autopsies. Br J Dermatol 77:431-438, 1965. 3. Lewin K: Subungual epidermoid inclusions. Br J Dermatol 81:671-675, 1969. 4. Samman PD: The human toe nail, its genesis and blood supply. Br J Dermatol 71:296-302, 1959. 5. Epstein W, Kligman A: The pathogenesis of milia and benign tumors of the skin. J Invest DermatoI26:1-II, 1956. 6. Zadek I, Cohen HG: Epidermoid cyst of the terminal phalanx of a finger. Am J Surg 85:771-774, 1953. 7. St Onge RA, Jackson IT: An uncommon sequel to thumb trauma: Epidermoid cyst. Hand 9:52-56, 1977.