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Presented by Ashley Cimino-Mathews, MD and prepared by Armen Khararjian, MD
This case talks about:
A 40 year-old male with a gluteal mass.
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Question 1 of 1
1. Question
Week 620: Case 1
A 40 year-old male with a gluteal mass.
Correct
Answer: Hibernoma
Histology: The core biopsy shows lobules of adipocytes with polygonal, granular and variably eosinophilic cytoplasm containing multiple small vacuoles. The nuclei are small, bland and either peripherally or centrally located. These morphologic features are characteristic of brown fat.
Discussion: The cytologic features of these cells are those of brown fat, and this mass lesion is termed a “hibernoma.” Normal brown fat is seen primarily in children, but residual brown fat can also be seen in adults as incidental findings (such as focal brown fat in the adipose tissue associated with a lymph node dissection). The differential diagnosis of hibernoma includes residual brown fat (which does not form a mass), fat necrosis, other fatty tumors such as lipoma and atypical lipomatous tumor/liposarcoma, granular cell tumors, and histiocytoid carcinomas. The diagnosis of a hibernoma is made on the histologic features alone, but like other fatty tumors, hibernomas are immunoreactive for S-100 protein and negative for CD68. Classic lipomas lack the granular vacuoles seen in hibernomas, and atypical lipomatous tumors/liposarcomas have nuclear atypia and lipoblasts. Granular cell tumors also have granular, eosinophilic cytoplasm, but they are not vacuolated and are immunoreactive for both S-100 protein and CD68. Histiocytoid carcinomas display nuclear atypia and are immunoreactive for cytokeratin.
Reference:
Furlong MA, Fanburg-Smith JC, Miettinen M. The morphologic spectrum of hibernoma: a clinicopathologic study of 170 cases. The American journal of surgical pathology. 2001;25(6):809-14.Incorrect
Answer: Hibernoma
Histology: The core biopsy shows lobules of adipocytes with polygonal, granular and variably eosinophilic cytoplasm containing multiple small vacuoles. The nuclei are small, bland and either peripherally or centrally located. These morphologic features are characteristic of brown fat.
Discussion: The cytologic features of these cells are those of brown fat, and this mass lesion is termed a “hibernoma.” Normal brown fat is seen primarily in children, but residual brown fat can also be seen in adults as incidental findings (such as focal brown fat in the adipose tissue associated with a lymph node dissection). The differential diagnosis of hibernoma includes residual brown fat (which does not form a mass), fat necrosis, other fatty tumors such as lipoma and atypical lipomatous tumor/liposarcoma, granular cell tumors, and histiocytoid carcinomas. The diagnosis of a hibernoma is made on the histologic features alone, but like other fatty tumors, hibernomas are immunoreactive for S-100 protein and negative for CD68. Classic lipomas lack the granular vacuoles seen in hibernomas, and atypical lipomatous tumors/liposarcomas have nuclear atypia and lipoblasts. Granular cell tumors also have granular, eosinophilic cytoplasm, but they are not vacuolated and are immunoreactive for both S-100 protein and CD68. Histiocytoid carcinomas display nuclear atypia and are immunoreactive for cytokeratin.
Reference:
Furlong MA, Fanburg-Smith JC, Miettinen M. The morphologic spectrum of hibernoma: a clinicopathologic study of 170 cases. The American journal of surgical pathology. 2001;25(6):809-14.
