**Core Concept:** Triphasic tumour is a term used to describe certain types of abdominal masses, particularly Wilms' tumor, which is the most common malignant kidney tumor in children. These tumors have three distinct components: a central area of necrosis, a peripheral zone of blastemal cells, and an intermediate zone of stromal cells.

**Why the Correct Answer is Right:** The correct answer, option D (Wilms' tumor), is identified as a feature of this tumour due to its specific histopathological characteristics. Wilms' tumor is characterized by the presence of small blue cells, which are the blastemal component. This component contributes to the triphasic nature of the tumor.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because the triphasic tumor does not solely consist of blastemal cells. The presence of a central area of necrosis and an intermediate zone of stromal cells further distinguishes it from a blastemal-only tumor.

B. This option is incorrect because it does not involve small blue cells, which are a key feature of the triphasic tumor. Wilms' tumor has small blue cells, while hepatoblastoma is characterized by large cells.

C. This option is incorrect because hepatoblastoma is a rare hepatic tumor in children that has distinct histopathological features, including the presence of large cells, not small blue cells.

**Clinical Pearl:** Wilms' tumor is a critical feature to recognize as it can lead to appropriate management strategies, such as nephrectomy (removal of the affected kidney) and adjuvant therapy (chemotherapy and/or radiotherapy) following surgery. Early recognition and prompt treatment are essential to improve patient prognosis and survival.