Pathology of Spitz Nevus, Atypical Spitz Nevus, Spitzoid Melanoma

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Pathology of Spitz Nevus,

Atypical Spitz Nevus and

Spitzoid Melanoma

Dr Sampurna Roy MD 2022

Sophie Spitz, in 1948, for the first time established the criteria to distinguish Spitz nevus from melanoma.

Spitz nevus mostly occurs in children and young adults.

Clinically, the tumour presents as a pink or flesh coloured papule or nodule, located on the face, trunk or extremities.

Histologically, Spitz nevus may be junctional, compound or intradermal.

The majority of Spitz nevi are compound lesions.

Microscopic images of Spitz Nevus:

Diagnostic criteria:
Major criteria:

1. Symmetry and sharp lateral borders (no lateral extension of junctional activity beyond the limits of dermal components).

Silhouette symmetry: an unsupportable histologic criterion for distinguishing Spitz nevi and compound nevi from malignant melanoma. Arch Pathol Lab Med. 1997 Jan;121(1):48-53.

2. Cell type- epithelioid and spindle cells.

Spindle cells are more common.

These cells are arranged in fascicles with vertical orientation related to the rete ridges.

3. Maturation of cells - Presence of small normal nevus cells in the deeper part of the lesion.

4. Absent pagetoid spread of single cells in most cases (when present, located in the center of the lesion);

5. Coalescent, pale pink Kamino bodies.

Multiple step sections may be necessay.

These are PAS and trichrome positive. Eosinophilic globules in spitz nevi: no evidence for apoptosis.Am J Dermatopathol. 1998 Dec;20(6):551-4.
Minor criteria

1. Junctional clevage

2. Hyperkeratosis and acanthosis.

3. Superficial multinucleate naevus cells

4. Perivascular inflammation

5. Absence of nuclear pleomorphism

6. No deep atypical mitoses (mitosis may be present in the junctional and superficial component.

7. Deep outlying, solitary naevus cells. Nevus cells drift inbetween collagen fibres.

8. Superficial edema, telangiectasia present.

9. Stratification of HMB-45 and cyclin D1 staining.

10. Low PCNA staining (only 2-3% of cells display Ki-67 in contrast to 15% in melanoma, p53 is expressed in occasional Spitz nevi).

Pathology of Atypical Spitz Nevus:

This lesion displays architectural and cytological atypia to a degree beyond to what is accepted as a benign Spitz nevus.

However, the features do not amount to clear cut malignant melanoma.

Atypical features may be subdivided into those involving the epidermis or the dermis/subcutis.

"Atypical" Spitz's nevus, "malignant" Spitz's nevus, and "metastasizing" Spitz's nevus: a critique in historical perspective of three concepts flawed fatally.

Cutaneous melanoma and atypical Spitz tumors in childhood.

Diagnostic clues to Atypical Spitz Nevus:

I -Intradermal variant:

A. Architectural disorder-

- 1. Disordered intraepidermal melanocytic proliferation (lentiginous and junctional nests).

- 2. Asymmetry,

- 3. Poorly circumscribed,

- 4. Lateral extension of intraepidermal component.

B. Cytological atypia-

Nuclear pleomorphism and enlargement.

Variation in nuclear chromatin pattern and nucleoli.

C. Host response-

Patchy chronic inflammation and fibroplasia

II -Dermal variant:

A. Architectural disorder.

Expansile nodule, increased cellularity, asymmetry, loss of cellular cohesion, deep extension, lack of maturation, ulceration, necrosis.

B. Cytological atypia.

C. Numerous atypical mitosis and mitosis at base of lesion.

Grading System:

Some authors have advocated a grading system to assess Atypical Spitz nevus: Spitz tumors in children: a grading system for risk stratification.

Spitz tumour is categorized into:

1. Low 2. Intermediate and 3. High risk groups.

Parameters studied for grading are as follows:

1. Age more than 10 years.

2. Diameter of lesion more than 10 mm.

3. Presence of ulceration.

4. Involvement of subcutaneous fat (level V)

5. Mitotic figures atleast more than 6 / mm2.

1. Halo Spitz nevus ; 2. Desmoplastic Spitz Nevus;

3. Plexiform Spitz nevus; 4. Pagetoid Spitz nevus ;

5. Angiomatoid Spitz nevus ; 6. Hyalinizing Spitz nevus

7. Recurrent Spitz nevus

Pathology of Spitzoid Melanoma:

Spitzoid Melanoma is malignant melanoma composed of spindle or epithelioid cells, and share morphological features in common with Spitz nevus.

The tumour has an aggressive behaviour and lead to metastasis.

Diagnostic clues to Melanoma:

1. Lack of maturation of cells at the base.

2. Presence of numerous deep or atypical mitoses.

3. Intraepidermal melanocytes (epithelioid type) below parakeratosis.

The melanocytes show pagetoid spread within the epidermis.

4. Dermal nests larger than junctional nests.

5. Deep extension in a bulbous manner into the fat (Clark level V).

Read related post: Desmoplastic Spitz Nevus

Morphological features provide valuable clues to the underlying genetic aberrations in spitzoid neoplasms.

Genetic aberrations can be found in the entire biological spectrum of spitzoid neoplasms (i.e. Spitz nevi, atypical Spitz tumors and spitzoid melanoma) and are, therefore, probably not useful for distinguishing benign from malignant tumours.

Genetic aberrations represent vital targets for therapeutic interventions and offer investigational treatment options for patients with metastatic disease.

The appearance of multiple epithelioid melanocytic tumors with BAP1 loss indicates a hereditary tumour syndrome.

Immediate genetic counselling and preventive screening of affected individuals is necessary in these cases.

Dermatopathology Quiz Case 60