A 52-year-old man from Mumbai presents with a 6-month history of progressive swelling of the right parotid region, facial pain, and trismus. Imaging shows a 4 cm heterogeneous mass with skin involvement. All of the following features suggest malignancy in this salivary gland tumor EXCEPT:

Explanation

## Malignant vs. Benign Salivary Gland Tumors: Clinical Distinction ### Clinical Features Suggesting Malignancy | Feature | Benign | Malignant | | --- | --- | --- | | **Growth rate** | Slow (years) | Rapid (weeks–months) | | **Facial nerve involvement** | Rare | Common (25–50%) | | **Skin involvement** | Absent | Present (fixation, ulceration) | | **Pain** | Absent | Often present | | **Trismus** | Absent | May indicate invasion | | **Imaging borders** | Well-defined, smooth | Ill-defined, infiltrative | | **Surrounding invasion** | No invasion | Invasion of muscle, bone, soft tissue | **High-Yield:** The classic triad of malignancy in salivary gland tumors is: (1) rapid growth, (2) facial nerve paralysis, and (3) skin involvement with fixation. ### Imaging Characteristics **Key Point:** Benign tumors (e.g., pleomorphic adenoma) show smooth, well-circumscribed borders with NO invasion of surrounding structures. Malignant tumors show ill-defined borders with infiltration into adjacent tissues, muscle, and bone. **Clinical Pearl:** In this case, the patient has rapid growth (6 months), facial pain, trismus, and skin involvement — all red flags for malignancy. However, the presence of a smooth, well-circumscribed border with no invasion of surrounding structures is a **benign feature** and does NOT suggest malignancy. ### Histological Subtypes of Malignant Salivary Tumors **Mnemonic: MASC** (Malignant salivary cancers) - **M**ucoepidermoid carcinoma (most common malignant parotid tumor) - **A**denocarcinoma (not otherwise specified) - **S**quamous cell carcinoma - **C**arcinoma ex pleomorphic adenoma Other malignancies: acinic cell carcinoma (low-grade), adenoid cystic carcinoma (perineural invasion, poor prognosis). ### Management Algorithm ```mermaid flowchart TD A[Salivary gland mass]:::outcome --> B{Clinical features of malignancy?}:::decision B -->|Rapid growth, FN palsy, skin involvement| C[Likely malignant]:::urgent B -->|Slow growth, no FN involvement, mobile| D[Likely benign]:::outcome C --> E[Wide local excision or parotidectomy with neck dissection]:::action D --> F[Superficial parotidectomy with FN preservation]:::action E --> G[Adjuvant RT/CT based on grade and stage]:::action ``` **Warning:** A smooth, well-circumscribed border on imaging is a **benign feature**. Malignant tumors characteristically show ill-defined, infiltrative borders. This is the ONLY option that does NOT suggest malignancy. [cite:Robbins 10e Ch 16] [cite:Park 26e Ch 11]