Spitz nevi in the classic histopathological pattern--lamb in wolf`s clothing

Abstract

Spitz nevus is a benign melanocytic lesion and also one of the main differential diagnosis of melanoma. A descriptive and retrospective study of surgical specimens from patients with a diagnosis of Spitz nevus was conducted at two institutions in Niterói - RJ. 32 cases were analyzed. The most frequent histological subtype was compound (60 %), with a predominance of epithelioid cells (17 cases - 53%). Pagetoid spread was observed in 21 cases (68%). Maturation of melanocytes was present in 13 cases (81%). Kamino bodies were found in eight cases (25%). Atypical melanocytes were present in 18 cases (56%). Mitoses were present in 11 cases (34%). Detailed knowledge of the classical form of Spitz nevi is essential for the differential diagnosis with melanoma. However, no single criterium is definitive in the differential diagnosis between Spitz nevus and melanoma.

FIGURE 1

Panoramic photo shows marked symmetry and circumscription, prominent skin alterations (orthokeratosis, hypergranulosis and acanthosis), nests of melanocytes perpendicular to the epidermis, artifactual cleft between the nests of melanocytes and the keratinocytes, and pigmentary incontinence (HE, original magnification - 15x)

FIGURE 2

Asymmetry and imperfect circumscription; orthokeratosis, hypergranulosis and acanthosis (HE, original magnification - 40x)

FIGURE 3

Numerous Kamino bodies associated with orthokeratosis, hypergranulosis, acanthosis and artifactual clefts between the nests of melanocytes and the keratinocytes (nest extrusion) (HE, original magnification - 100x)

FIGURE 4

Area of pagetoid spread, with irregular distribution of pigmentation and irregular maturation of melanocytes (HE, original magnification - 100x)

FIGURE 5

Lack of maturation. Atypical melanocytes with pleomorphism, anisocoria, cariomegaly and eosinophilic nucleoli (HE, original magnification - 400x)

FIGURE 6

Atypical melanocytes with pleomorphism, hyperchromasia and mitotic figure at the base of an intraepidermal nest (arrow) (HE, 400x magnification)

FIGURE 7

Spindle melanocytes forming nests in the epithelium of the skin appendages, located in a deeper position than the intradermal component (HE, original magnification - 100x)