Clinical History:

A 45-year-old man incurred abdominal trauma, and an exploratory laparotomy was performed. A ruptured splenic capsule was found, with hemoperitoneum, and a splenectomy was performed. During exploration, the surgeon observed a small, discrete, 0.7 cm mass beneath the serosa in the wall of the stomach, and it was resected.

This neoplasm is discrete and has well-defined borders (features of a benign tumor). It is composed of cells resembling mature adipocytes (the lipid has been dissolved out in routine tissue processing, leaving a clear space for cytoplasm that gives a grid-like appearance). The cell nuclei are pushed to the periphery of the cells by the stored lipid and are barely visible.

Questions:

1. What is the degree of differentiation?

This neoplasm is extremely well-differentiated, since it resembles normal adipose tissue. Benign neoplasms are always well-differentiated. In general, the degree of differentiation is helpful in grading a neoplasm, but grading schemes are applied to malignant neoplasms. In general, the better differentiated a tumor, the lower grade it is.

2. What is the malignant counterpart of this lesion?

Liposarcoma. Such a neoplasm would most likely be found in deep soft tissues in thigh or retroperitoneum, and it would probably be much larger. Lipomas can be found in a variety of locations and are generally small and incidental, without major problems resulting from their presence.