In-Service Exam
Melanoma - 2001





A 13-year-old boy has a pigmented, slightly raised nevus on the thigh. He has no history of malignant tumors and there is no family history of melanoma. Histologic examination of an excisional biopsy specimen of the lesion shows findings consistent with juvenile melanoma; the surgical margins are free of tumor.

Which of the following is the most appropriate next step?

(A) No additional treatment
(B) Referral to an oncologist for chemotherapy
(C) Interferon therapy
(D) Isolated limb perfusion
(E) Wide local excision

The correct response is Option A.

Benign juvenile melanoma is referred to by many terms, including Spitz nevus, spindle cell nevus, and epithelioid nevus. This solitary tumor is typically pink to red in color and is most likely to appear on the face in childhood. Although it can be initially mistaken for melanoma, histologic examination of a biopsy specimen will show giant spindle cells; it is believed to be a histologic variant of the compound nevus. Because it is benign, conservative treatment or complete excision is recommended. In this patient, no further treatment is required.

Chemotherapy, interferon therapy, limb perfusion, and wide excision are all options for management of malignant melanoma confirmed by histology.

References
1. Hurwitz S, ed. Clinical Pediatric Dermatology: A Textbook of Skin Disorders of Childhood and Adolescence. Philadelphia, Pa: WB Saunders Co; 1993:208-290.
2. Popkin GL. Tumors of the skin: a dermatologist's viewpoint. In: McCarthy JG, ed. Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1990;5:3592-3593.

PHOTO

The above photograph is of a 75-year-old woman who has a discolored 4-mm lesion of the nail bed of the nondominant left thumb after undergoing removal of the nail plate for management of chronic paronychia. A biopsy specimen of the lesion shows subungual melanoma with a thickness of 3 mm. The above MRI shows possible tumor tracking along the ulnar neurovascular bundle. Lymphoscintigraphy shows two positive nodes in the axilla.

Which of the following is the most appropriate level of amputation?

(A) Carpometacarpal joint
(B) Metacarpal diaphysis
(C) Metacarpophalangeal joint
(D) Proximal phalanx diaphysis
(E) Interphalangeal joint

PHOTO

The correct response is Option D.

This patient has a subungual melanoma, an uncommon, aggressive tumor most often seen in the thumb. Excisional biopsy should be performed immediately to distinguish this type of tumor from squamous cell carcinoma, basal cell carcinoma, pyogenic granuloma, glomus tumor, or giant cell tumor. Amelanotic tumors, which are often diagnosed late, comprise approximately 30% of all subungual melanomas. A Clark's level cannot be determined in patients with subungual melanoma because of the absence of subcutaneous tissue within the nail matrix. Although in situ melanomas are associated with a relatively good prognosis, all other forms of subungual melanoma are associated with poor prognoses. The outcome is particularly poor in patients with ulcerated lesions.

Patients with melanoma must be evaluated for the presence of local, regional, and distant metastases. Consultation with a medical oncologist is needed; MRI is helpful in determining the extent of local disease. However, the MRI findings may be confused with inflammatory changes. Melanomas can extend along the neurovascular bundles.

In patients with localized subungual melanomas, amputation just proximal to the most distal joint is recommended to clear disease while maintaining length and function of the digit. Sentinel node biopsy will determine tumor staging and the need for lymphadenectomy. In order to maintain thumb function following amputation, Z-plasty, detachment of the first dorsal interosseous tendon, and a more proximal reattachment of the adductor pollicis tendon can be performed to deepen the first web space and effectively lengthen the thumb.

More distal amputation will not clear local disease and will instead increase the risk for local recurrence. A more proximal amputation will not improve the poor prognosis and will also result in a significantly less functional digit, especially when the thumb is involved.

References
1. Kato T, Suetake T, Sugiyama Y, et al. Epidemiology and prognosis of subungual melanoma in 34 Japanese patients. Br J Dermatol. 1996;134:383-387.
2. Linares M, Hardisson D, Pena C. Subungual melanoma of the hand: unusual clinical presentation Ð case report. Scand J Plast Reconstr Surg Hand Surg. 1998;32:347-350.
3. Ogose A, Emura I, Iwabuchi Y, et al. Malignant melanoma extending along the ulnar, median, and musculocutaneous nerves: a case report. J Hand Surg. 1998;23A:875-878.
4. Quinn MJ, Thompson JE, Crotty K, et al. Subungual melanoma of the hand. J Hand Surg. 1996;21A:506-511.
5. Tubiana R, Gilbert A, Masquelet AC, eds. An Atlas of Surgical Techniques of the Hand and Wrist. Baltimore, Md: Williams & Wilkins; 1999:38-39.
6. Warso M, Gray T, Gonzales M, et al. Melanoma of the hand. J Hand Surg. 1997;22A:354-360.