Abstract: Spitz nevi are acquired melanocytic lesions with a wide histomorphological spectrum; reliable distinction from spitzoid melanoma is often difficult. Misdiagnoses of benign spitzoid tumors as spitzoid melanomas and vice versa are attributable to a frequently disturbing morphology and inconsistent or poorly defined histological criteria for diagnosis. Many recognized histological variants of Spitz nevi have been described, including the intradermal Spitz. Histopathologic descriptions of intradermal Spitz nevi have been done in the past; however, large studies addressing their histological spectrum have been lacking. We have retrospectively assessed the morphological features in 74 cases of intradermal Spitz nevi, excluding tumors clearly defined as atypical Spitz nevi and Spitzoid melanomas, to further delineate their histological spectrum. The patients' ages ranged from 5 to 81 years (median: 27). Anatomic location included: the upper extremities (27 cases), followed by head and neck (22 cases), lower extremities (9 cases), back (8 cases), buttock (5 cases), chest (1 case), and vulva (1 case). In 1 case, the anatomic location of the lesion was not available. Different histological variants were observed including hyalinized, polypoid, desmoplastic, angiomatoid, and halo Spitz. Morphological features evaluated included symmetry (100%), cell type (epithelioid 42%, spindle 16%, mixed 42%), maturation (85%), pigmentation (26%), chronic inflammation (24%), and mitotic activity (38%). Mild atypia was seen in 36 cases (49%), moderate atypia was seen in 28 cases (38%), and severe atypia was seen in 10 cases (14%). Intradermal Spitz nevus is a distinctive type of Spitz nevus that sometimes can be difficult to define given the unusual features that these lesions can show; thus, strict application of well-defined histological criteria and awareness of their morphological spectrum will facilitate definitive diagnosis.
*Associate Professor (J.A.P.), Pathology resident (D.D.S.), Chairman of Pathology (S.S.), Division of Dermatopathology, Department of Pathology, Medical College of Wisconsin, Milwaukee, WI;
†Head of Dermatopathology, University of Texas MD Anderson Cancer Center Department of Pathology, Houston, TX;
‡Dermatopathologist (D.K.), Head of Pathology (M.M.), Head of Dermatopathology (D.V.K.), Sikl's Department of Pathology, Charles University Medical Faculty Hospital, Pilsen, Czech Republic; and
§Head of Dermatopathology, Hospital Obrero Department of Pathology, La Paz Bolivia.
Reprints: Jose A. Plaza, MD, Division of Dermatopathology, Department of Pathology, Medical College of Wisconsin, 8701 Watertown Plank Rd, Milwaukee, WI 53226 (e-mail: firstname.lastname@example.org).
All authors and staff in a position to control the content of this CME activity and their spouses/life partners (if any) have disclosed that they have no financial relationships with, or financial interests in, any commercial organizations pertaining to this educational activity.