Dermatology MCQ - Infiltrative and Neoplastic Disorders - Spitz naevus

A 6-year-old child presents with a rapidly growing, pink, dome-shaped papule on the cheek that appeared 3 months ago. The lesion is 6 mm in diameter, symmetrical, and vascular with fine telangiectasia. There is no ulceration or bleeding. The most appropriate next step in management is:

A. Initiate a course of high-potency topical corticosteroids to reduce inflammation and slow growth.
B. Perform a shave biopsy to confirm the diagnosis, as this is the least invasive procedure.
C. Reassure the parents that this is a benign Spitz naevus and schedule follow-up in one year.
D. Perform a full-thickness excisional biopsy with a narrow (1-2 mm) margin for complete pathological assessment.
E. Order a PET-CT scan to rule out metastatic disease due to the rapid growth rate.

Correct Answer: D. Perform a full-thickness excisional biopsy with a narrow (1-2 mm) margin for complete pathological assessment.

Answer and Explanation

The correct answer is D. This question describes a classic presentation of a Spitz naevus. The key clinical clues are the young age, location on the face, rapid growth, and appearance as a pink, dome-shaped, vascular papule. However, despite the classic history, the definitive diagnosis of a Spitz naevus is histological. Furthermore, it is often histologically difficult to distinguish from spitzoid melanoma. Therefore, the standard of care is a complete excisional biopsy. This provides the pathologist with the entire lesion, allowing for assessment of crucial architectural features like symmetry, maturation, and the deep margin, which are essential for an accurate diagnosis.

Why the Other Options are Incorrect:

• A. Initiate a course of high-potency topical corticosteroids...: This is incorrect. Corticosteroids have no role in the management of a melanocytic proliferation. The "rapid growth" is a feature of the nevus itself, not inflammation that would respond to steroids.

• B. Perform a shave biopsy...: This is incorrect and can be a critical error. A shave biopsy often fragments the lesion and does not allow for evaluation of the deep and lateral margins or the overall architecture. This incomplete sampling can make the distinction between a benign Spitz naevus and a malignant spitzoid melanoma impossible, leading to diagnostic uncertainty and potentially requiring a more extensive re-excision.

• C. Reassure the parents and schedule follow-up...: This is incorrect. While the history is classic, the clinical appearance of a Spitz naevus can be indistinguishable from melanoma, and rapid growth is a red flag that always warrants a pathological diagnosis. Observation without a biopsy is not safe practice.

• E. Order a PET-CT scan...: This is incorrect and represents extreme over-management. A PET-CT is a high-radiation study used for staging known malignancies. There is no role for it in the initial diagnosis of a small, solitary, cutaneous lesion, even one with rapid growth.

Additional High-Yield Information for Exams:

• Histopathology: Key features include:

  • Large, epithelioid and/or spindled melanocytes with abundant, pink cytoplasm.

  • Nesting pattern ("raining down" or "hanging" nests).

  • Clefting around nests.

  • Epidermal hyperplasia.

  • Maturation with descent into the dermis (cells get smaller deeper down).

  • Kamino bodies: Globular, eosinophilic deposits at the dermo-epidermal junction (PAS-positive, diastase-resistant).

  • The distinction from melanoma relies on a combination of symmetry, maturation, and lack of severe atypia and mitotic activity, especially deep mitoses.

• Differential Diagnosis: The primary and most critical differential is Spitzoid Melanoma. Features favoring melanoma include older age, large size (>1 cm), ulceration, high mitotic rate, deep mitoses, and asymmetry.

• Prognosis: A classic, benign Spitz naevus has an excellent prognosis. Once completely excised, recurrence is rare, and the lesion is considered cured.

• Management & Rationale:

  • Rationale: To obtain a definitive histological diagnosis to rule out the spitzoid melanoma mimic.

  • First-line: Complete excisional biopsy is the gold standard.

  • After Diagnosis: If the pathology report confirms a benign Spitz naevus with clear margins, no further treatment is needed. If the margins are involved, a conservative re-excision may be recommended, particularly if there is any diagnostic uncertainty in the original report.

  • Atypical Spitz Tumour: For lesions with atypical features that fall short of melanoma, wider excision and sentinel lymph node biopsy may be considered in a multidisciplinary setting, though this remains an area of controversy.