**Core Concept**
Café-au-lait spots are a type of skin hyperpigmentation characterized by well-defined, light brown macules. They are a common feature of neurofibromatosis type 1 (NF1), a genetic disorder caused by mutations in the NF1 gene. Café-au-lait spots are typically present at birth or appear during infancy and are often one of the earliest signs of NF1.

**Why the Correct Answer is Right**
Café-au-lait spots are a diagnostic criterion for NF1, and their absence does not rule out the diagnosis. However, they are not typically seen in other conditions such as tuberous sclerosis complex (TSC), a different genetic disorder characterized by hamartomatous lesions. TSC is caused by mutations in either the TSC1 or TSC2 gene.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because NF1 can present with café-au-lait spots, and their absence does not rule out the diagnosis.
**Option B:** Incorrect because TSC is a different genetic disorder with distinct diagnostic criteria, and café-au-lait spots are not typically seen in TSC.
**Option C:** Incorrect because other conditions such as McCune-Albright syndrome can present with café-au-lait spots, and their absence does not rule out the diagnosis.

**Clinical Pearl / High-Yield Fact**
Remember that café-au-lait spots are a common feature of NF1, but their absence does not rule out the diagnosis. A comprehensive evaluation, including genetic testing and imaging studies, is necessary to confirm the diagnosis of NF1.

**Correct Answer: B. Tuberous sclerosis complex.**