**Core Concept**
Gardner's syndrome is a variant of Familial Adenomatous Polyposis (FAP), characterized by the presence of multiple colorectal adenomas, osteomas, and soft tissue tumors. It is an autosomal dominant genetic disorder caused by mutations in the APC gene, leading to uncontrolled cell growth and tumor formation.

**Why the Correct Answer is Right**
Gardner's syndrome is associated with the development of multiple colorectal adenomas, which are precancerous lesions that can progress to colorectal cancer if left untreated. The syndrome also involves the presence of osteomas, which are benign bone tumors, and soft tissue tumors, such as desmoid tumors and epidermoid cysts. The APC gene mutation leads to the activation of the Wnt/β-catenin signaling pathway, promoting cell proliferation and tumor formation.

**Why Each Wrong Option is Incorrect**
* **Option A:** is incorrect because Gardner's syndrome is indeed associated with osteomas, which are a hallmark of the disorder. Osteomas are benign bone tumors that can occur in various parts of the body, including the skull, jaw, and long bones.
* **Option B:** is incorrect because Gardner's syndrome is not typically associated with medullary thyroid carcinoma. Medullary thyroid carcinoma is a type of thyroid cancer that is associated with multiple endocrine neoplasia (MEN) syndromes, but not with Gardner's syndrome.
* **Option C:** is incorrect because Gardner's syndrome is not typically associated with pheochromocytoma. Pheochromocytoma is a type of adrenal gland tumor that is associated with MEN syndromes, but not with Gardner's syndrome.
* **Option D:** is incorrect because Gardner's syndrome is indeed associated with desmoid tumors, which are a type of soft tissue tumor that can occur in various parts of the body.

**Clinical Pearl / High-Yield Fact**
Gardner's syndrome is a classic example of a genetic disorder that can be prevented with early screening and treatment. Regular colonoscopy and polyp removal can prevent the development of colorectal cancer in individuals with FAP and Gardner's syndrome.

**Correct Answer:** B.