**Core Concept**
Rhabdomyosarcoma is a type of soft tissue sarcoma that arises from skeletal muscle cells. The diagnosis of rhabdomyosarcoma often involves histopathological examination of tumor tissue, which may require specific special stains to confirm the presence of muscle cells.

**Why the Correct Answer is Right**
The correct special stain used for the diagnosis of rhabdomyosarcoma is Masson's trichrome stain. This stain helps to highlight the presence of striated muscle cells by differentiating between muscle and non-muscle tissue. Masson's trichrome stain uses a combination of aniline dyes and acidic solutions to produce a blue-stained background, which allows for the visualization of red-stained muscle cells. The use of Masson's trichrome stain is particularly useful in identifying the characteristic striations and cross-striations of rhabdomyoblasts.

**Why Each Wrong Option is Incorrect**
**Option A:** H&E (Hematoxylin and Eosin) stain is a general-purpose stain that is often used in histopathology, but it is not specific for diagnosing rhabdomyosarcoma.
**Option B:** Periodic Acid-Schiff (PAS) stain is used to identify glycogen-rich structures, such as those found in some types of cancer, but it is not specific for rhabdomyosarcoma.
**Option C:** Gomori's trichrome stain is another type of trichrome stain, but it is not typically used for the diagnosis of rhabdomyosarcoma.

**Clinical Pearl / High-Yield Fact**
When interpreting histopathological slides, it is essential to consider the clinical context and to use a combination of special stains to confirm the diagnosis. In the case of rhabdomyosarcoma, Masson's trichrome stain is a critical tool for identifying the characteristic muscle cells that are diagnostic of this tumor.

**Correct Answer:** C. Masson's trichrome stain.