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nodular melanoma

Second most common of tumors that arise in melanocytes of individuals with white skin. Etiology: (risk factors) 1) precursor lesions a) congenital melanocytic nevus b) dysplastic (Clark's) melanocytic nevus 2) family history of melanoma 3) light skin color with inability to tan 4) excessive sun exposure, especially during preadolescence 5) HCTZ (RR=1.2) [4] Epidemiology: 1) median age 40-50 years 2) equal incidence in males & females 3) occurs in all races 4) 15-30% of melanomas in US 5) 8 times more common than superficial-spreading melanoma in Japanese 6) responsible for most melanoma deaths Pathology: 1) arises in the dermal-epidermal junction 2) extends vertically into the dermis 3) epidermal growth limited to a small groups of tumor cells also invading the dermis 4) surrounding epidermis is normal 5) tumor may show large epithelioid cells, spindle cells, small malignant melanocytes or mixtures of the 3 6) S100 & HMB-45 positive 7) the tumor is in the vertical growth phase from the onset 8) most aggressive form of cutaneous melanoma [3] Clinical manifestations: 1) uniformly elevated nodule or ulcerated thick plaque 2) may be reddish-blue (purple) or blue-black; either uniform in color or mixed with brown or black 3) may become polypoid & amelanocytic (pink) or tan 4) early lesions are 1-3 cm, but may grow much larger if undetected initially 5) oval or round with regular borders in contrast to other melanomas - most nodular melanomas are smooth, but others are eroded, portending poor prognosis 6) distribution: upper back (most common), legs, anterior trunk (same as superficial spreading melanoma), on arms & legs in Japanese 7) arises within 2-4 months to 2 years from normal-appearing skin or a melanocytic nevus Laboratory: 1) excisional biopsy with narrow margins 2) punch biopsy is acceptable when total excision is not feasible or impractical Complications: - nodular melanomas - account for 14% of invasive melanomas - responsible for 43% of melanoma deaths [3] Differential diagnosis: 1) hemangioma: red or pink, can be blue or purple, slow growth 2) pyogenic granuloma 3) pigmented basal cell carcinoma - rolled, pearly, translucent borders, arborizing telangiectasias - dermoscopy distinguishes clinically 4) keratoacanthoma - appears rapidily within 4-6 weeks as a round pink nodule with a central, keratin-filled crater - not black Management: (same for superficial spreading & acral melanoma): 1) examine regional lymph nodes 2) surgical excisions a) melanoma in situ - excise with > 5mm margin b) thickness < 1 mm 1] excise with 10 mm margin 2] excise down to fascia or muscle if no underlying fasica 3] direct closure without graft often possible 4] node dissection only if palpable & suspscious for metastasis c) thickness 1-4 mm 1] excision with 20 mm margin 2] excise down to fascia or muscle if no underlying fasica 3] regional lymphadenectomy if sentinel node procedure is positive 4] lymph node dissection if regional lymph nodes are palpable d) thickness > 4 mm 1] excision with 30 mm margin 2] excise down to fascia or muscle if no underlying fasica 3] lymph node dissection if regional lymph nodes are palpable 3) adjuvant chemotherapy a) interferon alpha-2b b) melphalan

Related

superficial spreading melanoma

General

cutaneous melanoma

References

  1. Color Atlas & Synopsis of Clinical Dermatology, Common & Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY, 1997, pg 202-203
  2. Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 544
  3. Mar V et al. Nodular melanoma: A distinct clinical entity and the largest contributor to melanoma deaths in Victoria, Australia. J Am Acad Dermatol 2012 Nov 21 PMID: 23182058
  4. Pottegard A, Pedersen SA, Schmidt SAJ et al Association of Hydrochlorothiazide Use and Risk of Malignant Melanoma. JAMA Intern Med. Published online May 29, 2018. PMID: 29813157 https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2682616