Indian Journal of Pathology and Microbiology
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Year : 2011  |  Volume : 54  |  Issue : 4  |  Page : 817-818
Vulvar hibernoma

1 Department of Cellular Pathology, PathLinks Pathology Service, Lincoln County Hospital, Lincoln, United Kingdom
2 Institute for Gynaecology and Obstetrics, Clinical Centre of Serbia, Belgrade, Serbia

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Date of Web Publication6-Jan-2012


A 35 year old woman presented with 18 months history of a painless, soft, well-circumscribed, vulvar subcutaneous lump which measured approximately 7 cm. The lesion was completely excised and microscopically was consistent with a hibernoma. According to the available literature in English, this is the first reported case of hibernoma of the vulva.

Keywords: Brown fat, hibernoma, vulva

How to cite this article:
Sheth A, Terzic M, Arsenovic N. Vulvar hibernoma. Indian J Pathol Microbiol 2011;54:817-8

How to cite this URL:
Sheth A, Terzic M, Arsenovic N. Vulvar hibernoma. Indian J Pathol Microbiol [serial online] 2011 [cited 2022 Jan 26];54:817-8. Available from: https://www.ijpmonline.org/text.asp?2011/54/4/817/91532

   Introduction Top

The brown adipose tissue is a specialized form of fat found in the hibernating and non hibernating animals and humans. In humans, it is usually found as persisting vestigial remnants along the esophagus, trachea, posterior neck and around the great vessels of the mediastinum. Hibernoma is a rare, benign tumor that arises mostly in adults. It is composed of multivacuolated adipocytes with small central nuclei. There have been small number of cases of this neoplasm reported, and according to the available literature, this is the first and unique case of hibernoma of the vulva.

   Case Report Top

A 35 year old woman presented to our outpatient clinic with an 18 weeks history of a painless, gradually enlarging subcutaneous mass at mons pubis. Prior to presentation, she had no reported significant history. Clinical examination revealed an approximately 7 cm large, soft, non tender, mobile lump on anterior portion of the vulva. There was no associated inguinal lymphadenopathy. After preoperative evaluation, the lesion was excised with the clinical diagnosis of a lipoma and the patient remained free of symptoms following the excision.

Macroscopic and Microscopic Features

Grossly, the specimen consisted of a 6 × 5 × 1.5 cm lump of dark yellow soft tissue covered by a delicate and translucent membrane [Figure 1]. On sectioning, the cut surface displayed greasy, yellow-brown, muscle-like appearance with no evidence of haemorrhage or necrosis [Figure 1].
Figure 1: Macroscopic images of the specimen showing a dark yellow soft tissue mass covered by a delicate and translucent membrane. The cut surface is greasy, yellow-brown and muscle-like

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Histological examination revealed a neoplasm composed mostly of multivacuolated brown fat cells with abundant, granular, eosinophilic cytoplasm and small, central nuclei [Figure 2]. Neither mitoses nor cellular atypia were found. The features were consistent with the diagnosis of a hibernoma.
Figure 2: Neoplasm composed of multivacuolated brown fat cells with abundant granular eosinophilic cytoplasm (Hematoxylin and eosin, ×100) Inset (Hematoxylin and eosin, ×200)

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   Discussion Top

Hibernoma is a rare, benign adipose tissue tumor. It shows differentiation towards brown fat and has received its name due to morphologic similarity to hibernating glands of animals. This tumour arises in adults and shows peak incidence in the third decade. The reported age range is from 2 to 72 years. It usually grows slowly and is painless. Tumor size can range from 1 to 24 cm with an average dimension of 9.3 cm. [1] Macroscopically, hibernomas are soft, well circumscribed and tan to red brown on cut section. Microscopically, hibernomas show a distinct lobular pattern and are composed of cells that show varying degrees of differentiation. Four histological variants including typical, myxoid, spindle cells, and lipoma-like have been described. The typical variant of hibernoma shows often equal numbers of pale and eosinophilic multivacuolated cells. The eosinophilic cell subtype is composed of at least 50% of hibernoma cells with deeply eosinophilic, granular cytoplasm. [1] Excision is curative and there appears to be no tendency for local recurrence.

Brown fat is more prevalent in fetal and neonatal ages. It is known to play an important role in thermoregulation and endocrine functions. Its amount decreases with age. The human depots are located in the supraclavicular and the neck region with some additional paravertebral, mediastinal, para-aortic, and suprarenal localizations. Previously, it was thought that the most common site of occurrence of hibernomas is in areas of residual brown fat. However, as per the study of the largest series of hibernomas, this tumor is most commonly found in the thigh [1] where residual brown fat has not been described. Hibernomas have also been described in the other anatomic locations including shoulder, back, neck, chest, arm, abdominal cavity, retroperitoneum, axilla, groin, supraclavicular area, buttock, scalp, abdominal wall, breast, spermatic cord, and perirectum. [1]

Lipomas have been described in the vulva, but to the best of our knowledge, no case of vulvar hibernoma has so far been reported in the English literature.

Residual brown fat has not been described in vulva and as suggested by Mary et al. ,[1] hibernomas may represent altered programming of the neoplastic fat cells towards brown fat differentiation.

   References Top

1.Furlong MA, Fanburg-Smith JC, Miettinen M. The morphologic spectrum of hibernoma: A clinicopathologic study of 170 cases. Am J Surg Pathol 2001;25:809-14.  Back to cited text no. 1

Correspondence Address:
Anuradha Sheth
Department of Histopathology, Lincoln County Hospital, Greetwell Road, Lincoln
United Kingdom
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.91532

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