## Core Concept
Krukenberg tumors are a type of metastatic tumor in the ovaries, typically originating from a primary site elsewhere in the body, most commonly the gastrointestinal tract, particularly the stomach. They are characterized by mucin-filled signet-ring cells. The key concept here is to understand the primary sites and histological features associated with Krukenberg tumors.

## Why the Correct Answer is Right
The correct answer, which is not provided, relates to the exception among the given choices regarding Krukenberg tumors. Generally, Krukenberg tumors are known for their origin from gastric carcinoma (most common), but they can also arise from other parts of the gastrointestinal tract and rarely from other sites. The histological hallmark is the presence of signet-ring cells. Understanding the common primary sites and the histological features helps in identifying the correct exception.

## Why Each Wrong Option is Incorrect
- **Option A:** If option A mentions a common primary site for Krukenberg tumors, such as the stomach, it would be incorrect as an exception.
- **Option B:** If option B refers to a characteristic feature of Krukenberg tumors, like signet-ring cells, it would not be the exception.
- **Option C:** Similarly, if option C describes another typical aspect of Krukenberg tumors, it would be incorrect as an exception.
- **Option D:** This would be the correct statement regarding an exception if it describes something not characteristic of Krukenberg tumors.

## Clinical Pearl / High-Yield Fact
A key point to remember is that Krukenberg tumors most commonly metastasize to the ovaries from a gastric primary site. Clinically, they can present with symptoms related to ovarian enlargement or as part of a more widespread metastatic disease. A classic clinical correlation is that Krukenberg tumors are often associated with a poor prognosis.

## Correct Answer: D.