Dermatology Online Journal

Cytological diagnosis of subcutaneous fat necrosis of newborn: A case report
Dr G K Parvathidevi MD, Dr M R Vijayashankar MD DVD, Dr CS Belagavi MD FICP FIMSA, Dr Deepak MD, Dr Vijaya MD, Dr G Narendra MD, Dr Ramesh MD
Dermatology Online Journal 11 (3): 20

Department of Pathology, Sri Siddhartha Medical College. Tumkur. hvss77@yahoo.com

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Abstract

Cytological findings of subcutaneous fat necrosis of the newborn, a rare and transient disorder of neonates, is described in a 20-day-old male baby, who presented with a 2-week history of firm, erythematous nodules and plaques on the back and upper arms.

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Introduction

Subcutaneous fat necrosis of newborn is an uncommon and self-limited disorder characterized by firm, erythematous nodules and plaques on the trunk, arms, back, buttocks, thighs, and cheeks of full-term newborns. We report the fine needle aspiration cytology findings in this rare disorder, which forms the second such case report in English literature.

Clinical synopsis

Figure 1	Figure 2
Figure 1. Purplish nodules over infants back.
Figure 2. Nodules on the back

A 3-week-old infant had been born at 40 weeks of gestation. The birth weight was 3600 g. Clinically, perinatal asphyxia was noted with aspiration of meconium. The infant was otherwise well developed. Because labor had been difficult, a forceps delivery was done. Within a few days of birth, diffuse erythematous skin discoloration was noted with formation subcutaneous purplish nodules over the infants back and upper arms (Figs. 1-3). All laboratory investigations were normal except for hypercalcemia in the range of 2.76 - 2.98 mmol/L (normal 2.25-2.49). Fine needle aspiration of a subcutaneous nodule on the back was undertaken for cytological study using a 23-gauge needle. The smears were stained with hematoxylin-eosin (H & E) and MGG (May Grunwald Giemsa), which revealed many necrotizing fat cells of varying size with needle-like crystals (Fig. 4). These crystals were doubly refractile and arranged in radial pattern or starburst pattern. A varying amount of inflammatory infiltrate was noted at the periphery of the fat cells, which was composed of lymphocytes, histiocytes, and multinucleated giant cells. The diagnosis of subcutaneous fat necrosis (SFN) was rendered. Culture of aspirated material revealed no growth. Biopsy of the lesion revealed the same features as fine needle aspiration cytology (FNAC) (Figs. 5-7). On followup the diffuse skin lesions regressed, and at the age of 7 weeks the child was in good health.

Figure 3	Figure 4
Figure 3. Large fat cell with multiple needle like crystals against hemorrhage and necrotic background. (H&E × 400)
Figure 4. Large fat cells with needle like crystals along with purplish blue calcium deposits and inflammatory infiltrate (H&E × 100)

Figure 5	Figure 6
Figures 5 and 6. Fat cells with needle-like crystals along with mixed inflammatory cells (H&E × 400).

Discussion

Subcutaneous fat necrosis of the newborn is a rare and self-limited condition characterized by firm, erythematous or blue-red nodules and plaques involving the trunk, arms, buttocks, thighs, and cheeks of full term newborns [1]. Lesions appear in first several weeks of life and resolve spontaneously in several weeks to 6 months without any treatment, but may be complicated by hypercalcemia and other metabolic abnormalities [2]. In our case, lesions appeared after 1 week of birth and mild hypercalcemia was noted. The exact etiology of this condition is unknown. The possibility of initiation by ischemic injury with trauma from forceps or pressure against the bony pelvis during labor has been suggested [3]. Other theories include a deficiency in brown fat [4] and defect in fat composition and metabolism combined with a stressful event [5]. Most neonates with this condition have had perinatal asphyxia or a difficult labor. These clinical settings were found in our case and FNAC findings were typical of subcutaneous fat necrosis. As in our case, some infants experience hypercalcemia [8]. This warrants close observation; reassurance is essential because SFN is a transient and self healing condition. The differential diagnosis includes sclerema neonatorum, which occurs in preterm infants with the involvement of whole body, is usually associated with debilitating diseases, and is fatal. FNAC in this condition reveals only large fat cells with needle-like crystals, with little or no fat necrosis, inflammation, or giant cells [7]. In the present case typical findings of many necrotizing fat cells with needle-like crystals along with lymphocytes, histiocytes and multinucleated giant cells [9] were seen, which prompted the diagnosis of SFN. Also culture report was negative, which ruled out the possibility of pyemic abscesses. Biopsy was also performed, revealing similar findings of the FNAC. Because tissue biopsy is an invasive procedure, FNAC should be done as the first line of investigation in suspected cases of subcutaneous fat necrosis of the newborn. In our opinion FNAC would not only obviate the need for a more invasive procedure such as tissue biopsy, but would also provide a prompt and correct diagnosis with less invasive technique.

References

1. Schulzke S. Fahnestich H. Buchner S. Subcutaneous fat necrosis of newborn. www.neonet.ch/cotm/html/body-case - 1. Feb.03.html.

2. Irwin M. Freedberg et al.; FitzpatrickÕs Dermatology in General Medicine.6th edition. MC Graw-Hill Publishers .vol 2, PP1369-70.

3. Potter EL. Craig JM: Pathology of the Fetus and the Infant. 3rd edition, Chicago, year book of Medical publishers, 1975, PP 642-644.

4. Taieb A. Douard D. Maleville J: Subcutaneous fat necrosis and brown fat deficiency. J.Am. Acad. Dermatol 1987; 16:624-625.

5. Silverman AK. Michels EH. Rasmussen JE: Subcutaneous fat necrosis in an infant, occurring after hypothermic Cardiac surgery. J. Am Acad. Dermatol 1986; 15:331-336.

6. Golitz LE: Inflammatory diseases of skin. In: Silverberg SG. Delellis RA. Frable WJ, editors. Principles and Practice of Surgical Pathology and Cytopathology. 3rd edition. New York: Churchill Livingstone, 1997,371.

7. Lever WF. Lever GS: Inflammatory diseases of subcutaneous fat. In Histopathology of Skin. 7th Ed. Philidelphia: Lippincot Company, 1990; 279-280.

8. Thomsen RJ: Subcutaneous fat necrosis of the newborn and idiopathic hypercalcemia. Arch Dermatol 1980; 116:115-1158.

9. Gupta .R.K. Naran. S. Selby RE, Fine needle aspiration cytodiagnosis of subcutaneous fat necrosis of newborn. A case report Acta cytol 1995;39: 759-76

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