The benign neoplasm of ‘brown fat’ noted in oral/pharyngeal region is:

 # The benign neoplasm of ‘brown fat’ noted in oral/pharyngeal region is:

A. Lipoma

B. Hibernoma

C. Teratoma

D. Brown tumor

The correct answer is B. Hibernoma. 

Hibernomas are uncommon neoplasms of brown adipose tissue. The most frequent sites of occurrence include the thigh, shoulder, and back. Less common myxoid and spindle cell hibernoma variants are likely to be located in the posterior neck and shoulder. Hibernomas are benign lipomatous neoplasms and have no potential for malignant transformation.  Hibernomas contain brown fat, and the name was coined about the presence of brown fat in hibernating animals. First described by Merkel 1906, these tumors are similar to lipomas in clinical behavior but have unique imaging and histopathologic features. Hibernomas generally present in young adults with a mean age of 38. In summary, these tumors are:

• Composed of brown fat
• Represent benign neoplasms
• Generally well-circumscribed masses
• Generally are small in size
• Exhibit slow growth
• Histopathologically composed of brown fat cells
• Chief differential diagnosis include well-differentiated liposarcomas (WDLS)
• Most often involve the thigh, trunk, and chest.
• Rare locations seen in less than 10% of cases include retroperitoneal, thorax, and intraabdominal regions.
• Fewer than 20% are intramuscular in location.

Reference: Tafti D, Cecava ND. Hibernoma. [Updated 2023 May 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK570579/