Pseudoinfiltration in a Spitz nevus
Pseudoinfiltration in a acral nevus
(Pagetoid) infiltration in a superficial spreading melanoma
In some lesions, epidermal melanocytes, generally located mostly in the basal layer, appear in spinous, granular or horny layers (suprabasal melanocytes). In melanoma, this phenomenon, produced by the impact of a malignant melanocytic proliferation with the epidermis (pagetoid infiltration)[1], is virtually diagnostic, even if its absence does not exclude the diagnosis [2-3]. However, suprabasal melanocytes are not constantly a sign of malignancy. The particular microanatomic structure of the rete ridges, effects due to a tangential cut, and a high speedy in melanocytic growth can produce some histological pictures displaying suprabasal melanocytes, without malignancy. Such pictures, recognized with the term "pseudoinfiltration", occur in various types of nevi (Spitz nevi, Reed nevi, acral nevi, genital nevi, nevi of childhood, dysplastic nevi and common nevi) [4-6]. Infiltration and pseudoinfiltration, albeit often confused, can be histologically distinguished, just as dermal infiltration in a squamous cell carcinoma can be distinguished from the false infiltration of pseudocarcinomatous hyperplasia. Number of suprabasal melanocytes, epidermal layers involved, structure of neoformed epidermal spaces, spatial and topographical characteristics of the phenomenon often allow such distinction [2,4-5]. In a difficult field like that of histological differential diagnosis between melanoma and nevi, in which sinle features are not exclusive, but often somewhat shared, an evaluation of soprabasal melanocytes can become important in the diagnostic decision.
1. Allen Ac, Spitz S: Malignant melanoma. A clinicopathological analysis of the criteria for diagnosis and prognosis. Cancer 6: 1-45, 1953.
2. Urso C, Wolovsky M, Bondi R: L'infiltrazione epidermica nel melanoma. Pathologica 87: 42-44, 1995
3. Fallowfield ME, Cook MG: Pagetoid infiltration in primary cutaneous melanoma. Histopathology 20: 417-420, 1992.
4. Urso C, Giannini A, Bartolini M, Bondi R: Histological analysis of intraepidermal proliferations of atypical melanocytes. Am J Dermatopathol 12: 150-155, 1990.
5. Urso C, Bondi R: "Infiltrazione" e "pseudoinfiltrazione" dell'epidermide nelle lesioni melanocitiche. G Ital Dermatol Venereol 126: 197-199, 1991.
6. Haupt HM, Stern JB: Pagetoid melanocytosis. Histologic features in benign and malignant lesions. Am J Surg Pathol 19: 792.797, 1995.
page 4
The other pages
- Home Page: Dermatopathology - C. Urso, MD
- page 1: Melanoma of the skin
- page 2: Histologic diagnosis of cutaneous melanoma
- page 3: Melanoma arising in a melanocytic nevus
- page 4: Infiltration and pseudoinfiltration
- page 5: Sweat gland carcinomas
- page 6: The sentinel lymph node in cutaneous melanoma
- page 7: Bullous cutaneous diseases
- page 8: Spitz nevus
- page 9: Prognostic factors in cutaneous melanoma
- page 10: The dysplastic nevus
- page 11: Dermatofibrosarcoma protuberans
- page 12: Melanoma in situ
- last page: Questions, comments and opinions
page 13: Merkel cell carcinoma
page 14: Basal cell carcinoma
page 15: Melanoma in paediatric age