Cutaneous Oncology Flashcards

A 22-year-old patient with fair skin presents with multiple jaw keratocysts, palmar pits, and over 15 basal cell carcinomas diagnosed since their teenage years. A germline mutation in which of the following tumor suppressor genes is the most likely underlying cause of this patient's condition?

Answer: PTCH1

This patient's constellation of findings—multiple early-onset basal cell carcinomas, odontogenic keratocysts of the jaw, and palmar pitting—is classic for Nevoid Basal Cell Carcinoma Syndrome (NBCCS), also known as Gorlin syndrome. This autosomal dominant disorder is most commonly caused by a germline mutation in the PTCH1 gene, a key component of the Sonic Hedgehog signaling pathway.

A 65-year-old man has a biopsy of a plaque on his buttock. Histopathology reveals a band-like dermal infiltrate of atypical lymphocytes with cerebriform nuclei showing prominent epidermotropism and forming Pautrier's microabscesses. Which immunophenotype is most characteristic of the neoplastic cells in this condition?

Answer: CD3+, CD4+, CD8-

The clinical and histopathologic findings are classic for Mycosis Fungoides, the most common type of cutaneous T-cell lymphoma (CTCL). The neoplastic cells are typically mature, skin-homing helper T-cells. Their characteristic immunophenotype is CD3+ (pan T-cell marker), CD4+ (helper T-cell marker), and CD8- (cytotoxic T-cell marker). Loss of pan-T-cell antigens like CD7 is also common.

According to the American Joint Committee on Cancer (AJCC) 8th edition staging system for melanoma, which of the following findings defines a primary tumor as stage T1b?

Answer: A melanoma <0.8 mm in thickness with ulceration

The AJCC 8th edition revised the T1 criteria. A T1a melanoma is defined as being <0.8 mm thick without ulceration. A T1b melanoma is defined as either being <0.8 mm thick with ulceration OR being 0.8-1.0 mm thick, with or without ulceration. Mitotic rate is no longer used for T1 sub-categorization.

A 75-year-old immunosuppressed (renal transplant recipient) patient develops a rapidly growing, 3 cm ulcerated nodule on the scalp. A biopsy confirms squamous cell carcinoma (SCC). Which of the following features most significantly classifies this tumor as 'high-risk' according to NCCN guidelines?

Answer: The patient's immunosuppressed state

While tumor diameter (>2cm on the scalp is a high-risk feature) and location (scalp) contribute to risk, SCC arising in an immunosuppressed patient is considered a high-risk feature by itself. Immunosuppression is a major risk factor for aggressive behavior, recurrence, and metastasis in cutaneous SCC.

A patient with metastatic melanoma that has progressed after chemotherapy is started on pembrolizumab. What is the primary mechanism of action of this agent?

Answer: It is a monoclonal antibody that blocks the PD-1 receptor on T-cells, preventing immune suppression.

Pembrolizumab is an immune checkpoint inhibitor. It is a humanized monoclonal antibody that targets the programmed cell death-1 (PD-1) receptor on T-cells. By blocking the interaction between PD-1 and its ligands (PD-L1/L2) on tumor cells, it releases the 'brakes' on the immune system, allowing the patient's own T-cells to recognize and attack the melanoma.

An 80-year-old woman presents with a 1.5 cm firm, red-violaceous nodule on her sun-exposed forearm. A biopsy confirms Merkel cell carcinoma. Her physical exam reveals no clinically palpable lymphadenopathy. According to NCCN guidelines, what is the most appropriate next step for staging this patient's regional lymph node basin?

Answer: Sentinel lymph node biopsy (SLNB)

For patients with clinically node-negative Merkel cell carcinoma, a sentinel lymph node biopsy (SLNB) is the most reliable tool for identifying subclinical (micrometastatic) nodal disease. The status of the sentinel node is a powerful prognostic factor and is critical for accurate staging and guiding decisions about adjuvant therapy, such as radiation.