In a 6 months old cross breed sow, a marked splenomegaly (measuring about 85 cm) was observed, the spleen also had a pale coloration and a marbe-like appearance. In the peritoneal serous membranes small whitish nodular lesions could be seen with an appearance similar to a chronic peritonitis.

The histopathological study showed, both in the spleen and in the peritoneal lesions, a neoplastic round cell proliferation surrounded by an abundant proliferation of connective tissue. Polymorphonuclear eosinophilic leukocytes could be observed infiltrating this tissue. Morphological diagnosis was compatible with a Mastocytoma.

To confirm the diagnosis immunohistochemistry against C-kit receptor was done, with a positive outcome. Toluidin Blue stain revealed the presence of intracytoplasmic granules in the neoplastic mast cells.

It is a rare neoplasm in pigs, we had previously described a case affecting the skin: Cutaneous Mastocytoma.

Marked increase in size of the spleen, which presents a pale appearance.

Marked increase in size of the spleen, which presents a pale appearance.

Detail of the marble-like appearance of the splenic parenchyma.

Detail of the marble-like appearance of the splenic parenchyma.

Miliary nodular lesions in the serous membranes of the abdominal cavity (intestines, stomach, etc.)

Miliary nodular lesions in the serous membranes of the abdominal cavity (intestines, stomach, etc.)

Histopathological study. A: H&E staining shows neoplastic mast cells surrounded by a fibrous matrix and presence of eosinophils infiltrating the mass (arrowhead). B: These mast cells were positive for the immunohistochemical marker against C-kit receptor. C: Toluidine blue staining showed the presence of intracytoplasmic granules.

Histopathological study. A: H&E staining shows neoplastic mast cells surrounded by a fibrous matrix and presence of eosinophils infiltrating the mass (arrowhead). B: These mast cells were positive for the immunohistochemical marker against C-kit receptor. C: Toluidine blue staining showed the presence of intracytoplasmic granules.