A 68-year-old farmer from rural Maharashtra presents with a non-healing ulcer on the dorsum of his left hand for 8 months. He reports that it started as a small nodule which gradually enlarged and ulcerated. On examination, the lesion is 2 × 2 cm, indurated with raised, everted edges and a granulating base. There is regional lymphadenopathy. Dermoscopy shows keratin-filled crater and polymorphous vessels. Histopathology reveals infiltrative nests of malignant squamous cells with moderate differentiation and 4 mitoses per high-power field. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Squamous Cell Carcinoma (SCC) ### Key Clinical Features **Key Point:** The combination of non-healing ulcer, raised everted edges, granulating base, and regional lymphadenopathy in a sun-exposed site (dorsum of hand) in an elderly farmer is pathognomonic for cutaneous SCC. ### Histopathological Grading The Broders classification grades SCC based on the percentage of differentiated cells: | Grade | Differentiation | % Keratinization | Prognosis | Metastatic Risk | |-------|-----------------|------------------|-----------|------------------| | I | Well-differentiated | >75% | Excellent | <5% | | II | Moderately differentiated | 50–75% | Good | 5–15% | | III | Poorly differentiated | 25–50% | Fair | 15–30% | | IV | Anaplastic | <25% | Poor | >30% | This patient has **Grade II (moderately differentiated) SCC** with 4 mitoses/hpf, which indicates intermediate risk of metastasis and recurrence. ### Risk Stratification for Cutaneous SCC **High-Yield:** Risk factors for aggressive behavior include: - **Histological:** Poor differentiation (Grade III–IV), depth >4 mm, Clark level IV–V - **Clinical:** Size >2 cm, location on ear/lip/genitals, rapid growth, immunosuppression - **Molecular:** TP53 mutations, high mitotic rate (>4/mm²) **Clinical Pearl:** This patient has a 2 × 2 cm lesion with moderate differentiation and 4 mitoses/hpf — placing him in the **intermediate-risk category**. Regional lymphadenopathy suggests possible nodal involvement, warranting sentinel lymph node biopsy or imaging. ### Management Implications 1. **Surgical excision** with 4–6 mm margins (intermediate-risk lesions) 2. **Mohs micrographic surgery** if high-risk features or recurrent disease 3. **Lymph node assessment** — clinical examination ± ultrasound or CT given adenopathy 4. **Adjuvant therapy** — consider if positive nodes or extranodal extension 5. **Follow-up** — 3-monthly for 2 years, then 6-monthly ### Why Not the Other Options? - **Basal cell carcinoma:** Does not metastasize to regional lymph nodes; presents with pearly nodule or rodent ulcer, not everted edges - **Merkel cell carcinoma:** Rare neuroendocrine tumor; presents as rapidly growing nodule in elderly; immunohistochemistry shows CK20+ (paranuclear dot pattern), synaptophysin+ - **Keratoacanthoma:** Self-limited lesion with spontaneous involution over months; lacks regional lymphadenopathy and has better prognosis