Giuseppe Argenziano

Benign Melanocytic Tumors

Common scalp nevi in children and teenagers are classically pigmented, whereas most scalp nevi in adults are usually nodular and nonpigmented with a smooth or papillomatous, occasionally keratotic, surface. Scalp nevi have no documented risk for malignant transformation.

Flat Solitary Pigmented Lesions in the Elderly

The sentence “we are born and we will die without nevi” summarizes one of the key components of the diagnosis of atypical lesions in the elderly. Epidemiologic data demonstrated that the nevus count and prevailing nevus patterns are strongly influenced by age. Notably, nevus count increases from childhood to midlife and decreases thereafter. In light of these findings, if evolving nevi in adolescence are an expected finding and therefore do not require further interventions, a melanocytic skin lesion showing signs of growth in the elderly should raise the index for malignancy. Furthermore, any flat acquired melanocytic lesion in this age should be considered with caution since the majority of lesions in the elderly are persistent intradermal nevi (congenital type). Firstly termed as atypical lentiginous junctional melanocytic proliferations, indeed they are regarded nowadays as melanomas.

Lesions with Regression

Regression of pigmented skin tumors represents a peculiar biologic phenomenon with not fully elucidated significance.

Recurrent Nevi and Nevi with Sclerosing Features and Inflammation

Recurrent nevi are benign melanocytic nevi that regrow after incomplete surgical removal or traumatic injury. Recurrent nevi are biologically benign without a documented risk of malignant progression, but they pose diagnostic problems because their morphological features resemble those of melanoma. They are also commonly referred to as “pseudomelanomas.” The management of repigmentation within a scar after incomplete biopsy or other destructive procedures (i.e., laser and cryotherapy) depends on whether a prior histopathologic diagnosis confirming a benign tumor was obtained or not. In cases of regrowth without histopathologic diagnosis, immediate excision and histopathologic examination are mandatory to rule out melanoma unintentionally treated as benign tumor. When a prior histopathologic diagnosis reports a benign tumor, often no further interventions are performed. However, careful histologic reevaluation of the slides of the previous excision is strongly encouraged, in order to avoid a misclassification which potentially delays diagnosis and adequate treatment of recurrent melanoma. The differential diagnosis of newly developing pigmentation within a scar of a previous excision of a melanocytic lesion includes recurrent nevus, recurrent melanoma, and melanotic reactive pigmentation. As a general rule, a relatively rapid development of the repigmentation favors the diagnosis of a benign recurrence. This is confined within the scar, and, dermoscopically, a regularly pigmented network and thin parallel streaks are associated with reactive pigmentations, whereas an irregular prominent network, globules, streaks, and heterogeneous pigmentation are usually associated with a melanocytic proliferation. On the other side, melanomas tend to recur months if not years after excision at the edges of the scar in the normal skin. Dermoscopy may not reveal specific melanoma features, displaying only a heterogeneous, structureless pigmentation. Therefore, in the case of a recurrent pigmentation involving the normal skin around the scar, a biopsy specimen should be obtained to exclude a possible melanoma recurrence. Histological features, even in case of recurrent nevi, can be very worrisome as recurrent nevi generally present a rich junctional component, sometimes frankly atypical and, with epidermotropism, arising on a sclerotic dermis.

Melanocytic Atypical Lesions in Patients with Multiple Nevi

In patients with multiple nevi, management goals are early diagnosis of melanoma while avoiding unnecessary excisions of benign lesions.

Lesions on the Head and Neck

Head and neck area represents a “special” body site where the close collaboration of the dermatologist together with the pathologist is of uppermost importance for reaching a correct diagnosis and consequently an optimal patient management. On this body site, especially on chronically sun-damaged skin in adults and elderly individuals, clinical and dermoscopic differential diagnosis can be challenging.

Dermoscopy of Nonmelanocytic Skin Tumors

Dermoscopy is a widely accessible, inexpensive, and reliable noninvasive diagnostic tool that improves the accuracy of the clinical diagnosis of skin tumors. Most dermoscopic patterns correlate with specific histopathologic substrates. Accordingly, dermoscopy allows a better differentiation between specific subtypes of skin tumors. The common benign epithelial skin tumors, such as solar lentigo and actinic keratosis, typically display specific dermoscopic criteria, which allow their clinical recognition. The dermoscopic hallmark of all vascular tumors is a mixture of red-purple-blue at times black colors, which however present with different patterns. Adnexal tumors are generally considered as dermoscopic mimickers of basal cell carcinoma, but specific clues exist, facilitating the differential diagnosis. The sensitivity and specificity rate of dermoscopy in the diagnosis of basal cell carcinoma is reported to be 9 and 93 %, respectively. Dermoscopy reaches 98 % sensitivity and 95 % specificity in the diagnosis of actinic keratosis. Dermoscopy reaches 79 % sensitivity and 87 % specificity in the diagnosis of squamous cell carcinoma.